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Subject: "Hypothesis - comments invited" Previous topic | Next topic
PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014   Lincoln, US  Nikonian since 04th Jan 2010 Tue 19-Mar-13 06:08 PM
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"Hypothesis - comments invited"



As I have admitted many times, I'm more of a techie photographer than I am an artist - having enjoyed a lifetime's association with hardware and software development. My experiences lead me to be curious about the relative auto-focusing speed between the D4 and other Nikon DSLRs.

I doubt that I'll be challenged if I state that the D4 achieves faster autofocus than its stablemates. That being the case, I propose that the governing factor might well be the "beefier" battery used in the D4 - which may well allow greater surge currents during auto-focus than the lesser batteries used in other bodies.

Unfortunately, I sold my D4 but do have a couple of D800s which use the, somewhat puny, EN-EL15 batteries. I have a Nikon AC adapter with the matching connector for the EN-EL15 and have used this during lengthy AF fine-tuning tests. I have the potential to power D800s externally, either by a HD battery or the AC adapter.

Would anyone like to suggest a good way to quantify speed-of-AF during tests with different power options? Results might be dominated by the in-camera power circuitry, but could well depend on the capacity of the battery to maintain voltage during the surge current while auto-focusing.

Pete

  

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Reply message RE: Hypothesis - comments invited JosephK Silver Member Fellow Ribbon awarded for his excellent and frequent contributions and sharing his in-depth knowledge and experience with the community in the Nikonians spirit.
19th Mar 2013
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Reply message RE: Hypothesis - comments invited PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014
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Reply message RE: Hypothesis - comments invited avm247 Moderator Awarded for high skills in documentary architecture and aviation photography Donor Ribbon. Awarded for his support to the Fundraising Campaign 2014
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Reply message RE: Hypothesis - comments invited PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014
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     Reply message RE: Hypothesis - comments invited Ferguson Silver Member
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Reply message Hypothesis - comments invited PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014
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               Reply message RE: Hypothesis - comments invited Ferguson Silver Member
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               Reply message RE: Hypothesis - comments invited PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014
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                    Reply message RE: Hypothesis - comments invited Ferguson Silver Member
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               Reply message RE: Hypothesis - comments invited PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014
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                    Reply message RE: Hypothesis - comments invited avm247 Moderator Awarded for high skills in documentary architecture and aviation photography Donor Ribbon. Awarded for his support to the Fundraising Campaign 2014
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                         Reply message RE: Hypothesis - comments invited PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014
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                              Reply message RE: Hypothesis - comments invited avm247 Moderator Awarded for high skills in documentary architecture and aviation photography Donor Ribbon. Awarded for his support to the Fundraising Campaign 2014
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JosephK Silver Member Fellow Ribbon awarded for his excellent and frequent contributions and sharing his in-depth knowledge and experience with the community in the Nikonians spirit.   Seattle, WA, US  Nikonian since 17th Apr 2006 Tue 19-Mar-13 09:46 PM
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#1. "RE: Hypothesis - comments invited"
In response to Reply # 0



I would think that for some of this discussion you would need to qualify it as to what kind of focus motor is being used. For the camera's built-in screw motor, yes, a bigger motor and higher voltage would get you faster focus times. However, I am not sure how an increased voltage might affect the SWM components of an AF-S lens.

---------+---------+---------+---------+---------+
Joseph K
Seattle, WA, USA

D700, D200, D70S, 24-70mm f/2.8, VR 70-200mm f/2.8 II,
50mm f/1.4 D, 70-300mm f/4.5-5.6 VR, 18-70mm f/3.5-4.5 DX

  

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PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014   Lincoln, US  Nikonian since 04th Jan 2010 Tue 19-Mar-13 11:57 PM
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#6. "RE: Hypothesis - comments invited"
In response to Reply # 1




Joseph,
My feeling is that you make a good point with respect to determining the fastest achievable AF, but for COMPARISONS, there needs to be a finite amount of energy put into moving the focusing elements of a given lens. If high energy is available, the movement can be achieved in less time.

It's not always the voltage which matters, as much as the internal impedance of the power source.

Pete

  

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avm247 Moderator Awarded for high skills in documentary architecture and aviation photography Donor Ribbon. Awarded for his support to the Fundraising Campaign 2014   Rancho Cordova, US  Charter Member Tue 19-Mar-13 10:36 PM
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#2. "RE: Hypothesis - comments invited"
In response to Reply # 0



Pete, wouldn't you also have to take the AF sensor's sensativity into consideration? I'm thinking that by sticking to the center sensor location with a good X-section and contrasty subject you'll be able to AF speed.

You would also have to control light levels as that can effect AF speed, right?

Type of lens would also be an issue...internal focus (IF) have shorter rotational throw (angle?) vs. non-IF lenses (which are mostly older). Then there's the type of AF...integrated in the lens or in the body...AF-I and AF-S are so much faster than their helicoil brethern.

Lens speed might be another variable...primes may be faster than zooms expecially variable aperture lenses.

Do you have equipment to measure the time diferrence from say infinity focus to minimum distance focus?


Anthony

The Moderator Page and My Gallery
The important things in life are simple; the simple things are hard.

  

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PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014   Lincoln, US  Nikonian since 04th Jan 2010 Tue 19-Mar-13 11:52 PM
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#4. "RE: Hypothesis - comments invited"
In response to Reply # 2
Wed 20-Mar-13 12:20 AM by PeterBeckett


Hi Anthony,
I agree with the points you made, but my feeling is that it should be possible to QUANTIFY(see my OP) the time it takes for a given lens on a given body to focus.

I'm thinking that, for situations in which the AF speed may a critical factor (BIF, for example), it's not at all likely that anyone would select a "screwdriver" lens.

So, for a given body (in my case, a D800/E) and a given lens (perhaps an AFS 400mm/2.8G VRII or an AFS 70-200mm f/2.8G VRII) it might be possible to correlate a difference in time-to-AF with the voltage/internal impedance of the power source (which would be strictly maintained within the published Nikon specs).

We KNOW that Nikon once gave different CH rates with/without the use of external batteries in a "grip". Was that with the D3? Anyway, at that time the dominant power drain was probably the shutter and mirror motors.

I don't know if the limiting factor for shooting rate is the available power for mirror+shutter operation, or if it's the speed with which data can be stored on the memory card(s). I'll probably determine the maximum shooting rate vs power source, so then we will know if the former is still a factor.

Going back to the main question I posed in the OP, let me propose a strawman answer. Everybody please comment.

Assume a fixed target, at a decent distance from the camera - maybe 50ft or more. Assume a D800 with 400mm lens. Assume that the camera is electronically triggered by a custom programmed, microprocessor-based, controller. Assume also EITHER 1) a microphone close to the camera and whose output is fed to the controller, which is able to determine (and display) the time between triggering the camera and the microphone picking up the camera's "click". OR 2) I could use the PC flash trigger to indicate that the shutter had reached fully open. Before writing the code for such an experimental "controller", I would probably "breadboard" a really simple arrangement to see if I could make the measurements with an oscilloscope.

So, the camera's release would be set to focus priority and the lens focus set to the closest available. Using a variety(a small number) of power sources, I feel that it should be possible to MEASURE the delay between the "trigger" signal and when the mirror/shutter actuates. Hopefully, that time would be dominated by the time to AF.

Whaddya think?

Pete

Edited to add...
Although I didn't say so, by making the measurements mentioned WITHOUT AF, I will be able to determine the "overhead" time and that time OUGHT to be pretty constant. Then, after making an equivalent measurement with AF enabled, I should be able to determine the time-to-AF.

  

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Ferguson Silver Member  Cape Coral, US  Nikonian since 20th Aug 2004 Tue 19-Mar-13 11:56 PM
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#5. "RE: Hypothesis - comments invited"
In response to Reply # 4




>Assume a fixed target, at a decent distance from the camera -
>maybe 50ft or more. Assume a D800 with 400mm lens. Assume
>that the camera is electronically triggered by a custom
>programmed, microprocessor-based, controller. Assume also
>EITHER 1) a microphone close to the camera and whose output is
>fed to the controller, which is able to determine (and
>display) the time between triggering the camera and the
>microphone picking up the camera's "click". OR 2) I
>could use the PC flash trigger to indicate that the shutter
>had reached fully open. Before writing the code for such an
>experimental "controller", I would probably
>"breadboard" a really simple arrangement to see if I
>could make the measurements with an oscilloscope.

Hmmm... there might be a simpler way. Is there a documented API for tether control? If you had that, there MIGHT be feedback in the API for when it fires. A computer could easily time the difference between "shoot" and "have shot" (unless it mixes in download time of course). Or alternatively get some simple device that can detect the strobe on the PC and let it time between those two events.

You could even calibrate for USB speed difference but turning off AF and doing the same timing as the zero-difference baseline.


Linwood

Comments welcomed on pictures: Http://captivephotons.com

  

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Ferguson Silver Member  Cape Coral, US  Nikonian since 20th Aug 2004 Tue 19-Mar-13 11:52 PM
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#3. "RE: Hypothesis - comments invited"
In response to Reply # 0




I took a D4 and D800 and put a 70-200/F2.8 VR-I on, and set it to AF-S, twisted to infinity and hit focus. It runs all the way down, and back to infinity in about a second. UNfortunately I have only one lens and no accurate way to time it, but they "felt" the same.

But I'm not sure that's really what matters. There's obviously some amount of computation time in the mix -- whether it is significant or not (or overshadowed by mechanism movement) I do not know.

So a more meaningful test, but one that would be harder to do, is to put a real subject in view with the lens equally defocused and see how quickly it focuses. Much harder to time.

And another perhaps more meaningful test is whether they maintain focus equally well (tracking, continuous focus, rate of change of focus on moving object).

I don't envy you the task you set.

But I've always wondered how it can have the same focus system and be different.


Linwood

Comments welcomed on pictures: Http://captivephotons.com

  

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PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014   Lincoln, US  Nikonian since 04th Jan 2010 Tue 19-Mar-13 11:59 PM
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#7. "Hypothesis - comments invited"
In response to Reply # 3
Wed 20-Mar-13 12:03 AM by PeterBeckett


Hi Linwood,
It seems that we may have been typing concurrently.

What do you think of the approach I gave above, as a strawman?

Best,

Pete

  

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Ferguson Silver Member  Cape Coral, US  Nikonian since 20th Aug 2004 Wed 20-Mar-13 01:46 AM
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#8. "RE: Hypothesis - comments invited"
In response to Reply # 7



>Hi Linwood,
>It seems that we may have been typing concurrently.
>
>What do you think of the approach I gave above, as a
>strawman?

Actually I was responding to that and quoted it. I'm agreeing with you, suggesting that you might be able to do this without any hardware other than a PC, or at most a PC and a way to detect a flash (I wonder if some of the "popper" type devices may have something that can hook to a PC as well).

The D800 and D4 can both be computer controlled, I suspect the API is not hard to get it to do something really simple like "take a picture", as opposed to something custom built.



Linwood

Comments welcomed on pictures: Http://captivephotons.com

  

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PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014   Lincoln, US  Nikonian since 04th Jan 2010 Wed 20-Mar-13 02:05 AM
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#9. "RE: Hypothesis - comments invited"
In response to Reply # 8
Wed 20-Mar-13 02:09 AM by PeterBeckett


Hi again,
I'm now convinced that the measurement boils down to something REALLY simple, so here's my plan:
I will use an AWB (Arbitrary Waveform Generator) to create pulses at 10 second intervals, with a 1% duty ratio. Use those pulses, via a simple circuit, to trigger the camera AND provide a "start" signal to a digital timer/counter which will be given a "stop" signal when the PC closure occurs. The T/C will directly read the time (to a ridiculously high accuracy) from triggering the camera until the shutter becomes fully open.

The camera will be set to "M" and the average of several "shots" will be determined without/with AF (always starting with de-focus at one end of the scale when focus requires it to be close to the other end of the scale). These tests to be repeated with various power sources. The same setup will be used to TRY to determine the effect of the increased loading that is imposed on the power source by VR.

Although I now only own D800s, I'd like to be able to repeat the measurements using a D4.

Incidentally, I have developed several microprocessor-based gizmos that, among other things, trigger the D4 and D800 electronically. That's positively trivial!

Wouldn't it be interesting if the results showed that, for birding or sports, the D800 AF could be as fast as that of the D4 if a simple external battery were used!

Now you have my plan. Give me around a week or so, and I'll report results!

(But I am very much still open to further comments/suggestions!)

Pete

  

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Ferguson Silver Member  Cape Coral, US  Nikonian since 20th Aug 2004 Wed 20-Mar-13 02:55 AM
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#10. "RE: Hypothesis - comments invited"
In response to Reply # 9



>Wouldn't it be interesting if the results showed that, for
>birding or sports, the D800 AF could be as fast as that of the
>D4 if a simple external battery were used!

Wouldn't it be fascinating if you found that even with normal power the D800 and D4 focused at the same speed, and we learned it was all a "but I paid twice as much so it MUST be faster". I'm honestly of split personality on that subject, some days I feel they focus about the same, some days I feel the D4 is much faster. I'm curious to see numbers.


Linwood

Comments welcomed on pictures: Http://captivephotons.com

  

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PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014   Lincoln, US  Nikonian since 04th Jan 2010 Wed 20-Mar-13 03:32 AM
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#11. "RE: Hypothesis - comments invited"
In response to Reply # 10



Yup! Sure would!!!

I hope I'm not going to have to buy another D4 just so I can make the measurements. LOL.

Pete

  

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Ferguson Silver Member  Cape Coral, US  Nikonian since 20th Aug 2004 Wed 20-Mar-13 12:07 PM
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#12. "RE: Hypothesis - comments invited"
In response to Reply # 11



>Yup! Sure would!!!
>
>I hope I'm not going to have to buy another D4 just so I can
>make the measurements. LOL.

Better excuse than many of us probably used on that fateful day.

If I were anywhere nearby would certainly offer to come help, but I suspect there are people in S. Cal. who will.

Anxiously awaiting results....


Linwood

Comments welcomed on pictures: Http://captivephotons.com

  

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PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014   Lincoln, US  Nikonian since 04th Jan 2010 Wed 20-Mar-13 03:08 PM
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#13. "RE: Hypothesis - comments invited"
In response to Reply # 9
Wed 20-Mar-13 03:48 PM by PeterBeckett


OK, I dare not spend any more time on this project today, but I thought some of you might like to see the results of a simple, preparatory, test. The purpose of this is to determine the likelihood of the EP-5b being active.

O/C means "open circuit, with no load imposed"

O/C Output of EH-5a: 9.41644V
O/C Output of EP-5b when connected to EH-5a: 9.41644V
O/C Output of fully charged EN-EL15: 8.355V

While not absolutely conclusive, the above results strongly suggest that the EP-5b is passive. If so, that means the camera MIGHT WELL be able to take advantage of a heavy-duty external power source - but that will depend entirely on the camera's internal power circuitry!

The EN-EL15 voltage is likely to be about 7.4V when loaded, as it is probably based on 2x 3.7V Lithium cells.

I won't be able to make any further progress on this project until Friday, possibly the weekend.

Pete
Edited to correct wrong part number. I previously used DP-6, where I should have said EP-5b. I'm sorry for any confusion this might have caused!

  

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avm247 Moderator Awarded for high skills in documentary architecture and aviation photography Donor Ribbon. Awarded for his support to the Fundraising Campaign 2014   Rancho Cordova, US  Charter Member Fri 22-Mar-13 04:24 AM
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#14. "RE: Hypothesis - comments invited"
In response to Reply # 13



Sounds like a fun project, and I'd be interested in the testing process and results.


Anthony

The Moderator Page and My Gallery
The important things in life are simple; the simple things are hard.

  

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PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014   Lincoln, US  Nikonian since 04th Jan 2010 Fri 22-Mar-13 03:40 PM
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#15. "RE: Hypothesis - comments invited"
In response to Reply # 14



Hi Anthony,
I'm keen to proceed, but, unless my plans for today take less time than anticipated, am unlikely to make progress until Sunday and Tuesday (after the el cheapo AC power system for EN-EL15 cameras, arrives at around 5pm on Monday).

I will post explicit details of the test setup, results and conclusions.

I would appreciate hearing from anyone with a D4 who lives close to San Jose/Saratoga/Los Gatos/Cupertino and is willing to let me measure its AF speed with the same lenses as I use for my D800/E. The tests with the D4 will be TOTALLY SAFE as I will only use its regular battery.

Pete

  

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avm247 Moderator Awarded for high skills in documentary architecture and aviation photography Donor Ribbon. Awarded for his support to the Fundraising Campaign 2014   Rancho Cordova, US  Charter Member Fri 22-Mar-13 04:03 PM
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#16. "RE: Hypothesis - comments invited"
In response to Reply # 15



Pete, if you can't borrow one, what about a rental? (Insert my big, toothy grin here. )


Anthony

The Moderator Page and My Gallery
The important things in life are simple; the simple things are hard.

  

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PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014   Lincoln, US  Nikonian since 04th Jan 2010 Fri 22-Mar-13 04:36 PM
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#17. "RE: Hypothesis - comments invited"
In response to Reply # 16



Definitely "maybe"...

Pete

  

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PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014   Lincoln, US  Nikonian since 04th Jan 2010 Sat 23-Mar-13 07:56 PM
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#18. "RE: Hypothesis - comments invited"
In response to Reply # 0



Hi Everyone,
This message is really just a teaser! I decided to abort my scheduled plans for this morning in order to set up my test equipment for "this" project.

About all I'm going to say, for now, is that the test setup is working perfectly and there have already been a few surprises. I am able to accurately measure timings and current draw vs time. After initial test results, I decided to illustrate timings as oscilloscope traces - along with my interpretation. I am experimenting with options to capture the traces. As I don't have a licence for the very expensive support software to go with my 'scope, I'll probably have to resort to photographing the screens.

If all goes well, I hope to post results obtained using my D800 and a small selection of lenses, very early next week.

I will say that the surge currents are very high!!!

I'm still hoping to hear from someone who is willing to bring me a D4 to be tested...

Pete

  

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Stagecoach Silver Member  Suva, FJ  Nikonian since 03rd Apr 2009 Sun 24-Mar-13 09:15 AM
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#19. "RE: Hypothesis - comments invited"
In response to Reply # 18



Pete

Seems like you have got everything sorted for your tests but one thing that came to mind was another possibility for the timing measurement.

Would an electronic timer (stopwatch) that was triggered at exactly the same time as the camera been an option ? The camera could have been pointing at the timer to give the 'duration' record. It may have also been a good indication of focus repeatability accuracy .

Just a thought.

Grahame

Visit my Nikonians gallery.

  

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PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014   Lincoln, US  Nikonian since 04th Jan 2010 Sun 24-Mar-13 03:47 PM
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#20. "RE: Hypothesis - comments invited"
In response to Reply # 19



Thanks Grahame, but I'm doing everything electronically.

I detect when the shutter fires by using the PC flash trigger.

Pete

  

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PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014   Lincoln, US  Nikonian since 04th Jan 2010 Wed 27-Mar-13 08:44 PM
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#21. "RE: Hypothesis - comments invited"
In response to Reply # 0



Hi Everyone,
Well, after a few days working on other, more pressing but less interesting, projects, I was able to devote today to "this" one.

Since overcoming software problems associated with capturing traces from my oscilloscope digitally, I can now report that "all systems go". I was on the verge of setting up to shoot pictures of the screen!

Measurements will not involve a D4, just my D800, but the test matrix involves evaluating Auto-Focus time with more power sources than originally anticipated. I now have the means to make current measurements while auto-focusing with three types of batteries and three types of external Power supplies ("AC Adapters"). These measurements should offer a very good understanding of whether there is likely to be a difference between the D800 and a D4 with respect to Auto-Focus time.

Barring unforeseen problems, I expect to post results tomorrow.

Pete

  

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PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014   Lincoln, US  Nikonian since 04th Jan 2010 Thu 28-Mar-13 09:11 PM
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#22. "RE: Hypothesis - comments invited"
In response to Reply # 21
Thu 28-Mar-13 11:38 PM by PeterBeckett


Overall:
This post presents the results of a series of tests undertaken as part of a project whose original purpose was to determine whether AF might be faster with a D4 than with a D800. Unfortunately I sold my D4 a few months ago and have received no offers of one for testing. Nevertheless, the tests which I conducted yield evidence which suggests an answer to the original hypothesis.

Equipment used:
Batteries – Nikon EN-EL15 and Pearstone EN-EL15 look-alike
AC Adapters – Nikon EH-5a with EP-5b and Power2000 EN-EL15 AC adapter
Camera body - Nikon D800
Lenses – AF-S 70-200mm f/2.8G ED VRII, AF-S 400mm f/2.8G ED VR AF, AF-S 24-120mm f/4
Fluke bench multimeter 8846a
Oscilloscope - Tektronix TDS2024b (digital, 4-channel, 200MHz) with screen capture software
Various custom-made heavy-duty test leads etc., using Deans Ultra high current connectors
50milliohm, 4-terminal, non-inductive shunt for transient current measurements

Test Methodology:
While powered by one of the available power sources, the camera was triggered “remotely”. The trigger also initiated a three-channel oscilloscope trace which showed a) the trigger b) the current and c) the time at which the camera’s shutter became fully open (as indicated by the PC “flash” trigger).

The camera+lens was pointed at a target having major black/white banding located some 75 yards away. Only the central AF point was used. For each lens used, before triggering the camera, the focus was set to the minimum distance for the lens. In all cases, the camera was set for a shutter speed of 1/250.

Results:
First, I evaluated the no-load voltage and determined the effective internal impedance (resistance) of each power source with a load of 2 Ohms. i.e., with a load current of a little over 4 Amps.

Nikon EN-EL15 battery: 8.351V and 0.313 Ohms
Pearstone “EN-EL15”: 8.238V and 0.307 Ohms
Nikon EH-5a: 9.416V (with 100mV pk-pk HF noise) and 0.082 Ohms
Power2000: 9.126V (with 500-600mV pk-pk HF noise) and 0.166 Ohms

Observations a) There is no significant difference between the two batteries with regards to their ability to withstand high surge currents. b) The Nikon power unit appears to be noticeably “better” than the Power2000, but the differences may well be insignificant during real-world use.

Next, I evaluated timings and surge currents.

Note that in all charts, the purple trace is the camera trigger signal (i.e., shutter release). The camera is triggered when the signal goes “low”. The blue/green trace shows a pulse from the flash trigger, i.e., when the shutter has reached fully open. The orange trace shows the current being drawn from the power source. The X-axis is 100 mSec per major division and the Y-axis shows 1 Amp per major division.

Chart 1 shows that the camera actually takes a shot approximately 120mSec after receiving the trigger when AF is disabled. This chart also shows a peak current of around 3.6A. The current profile shows the mirror-up then the shutter release, then followed by restoring the mirror and shutter. It also shows a current of about 800mA being drawn while the image is processed and stored on the memory card. As no AF is involved, the timings and current profile shown in Chart 1 are independent of the particular lens used.

Charts 2 and 3 show that, when AF is used, there is no significant difference between timings or current profile when the camera is powered by an EN-EL15 or an EH-5a. The shot is exposed about 475mSec after the trigger. A 70-200mm f/2.8G (VRII) lens was used. Although not shown, I determined that AF time is unaffected by focal length with this lens.

Charts 4, 5 and 6 show a measurable difference between the AF times as a function of the power source when using a 400mm f/2.8G lens.
EN-EL15: 615mSec
EH-5a: 515mSec
Power2000: 625mSec

Overall Conclusions:
IMHO, it is NOT possible to draw any clear conclusion about whether the D4, with its heavier-duty battery than the D800, is likely to AF faster. The timings with the 400mm lens MIGHT be used to support the hypothesis, but I don’t believe the effect would be significant.

A secondary observation based upon my test results is that the Power2000 AC adapter, while not being quite as good a power supply as the Nikon EH-5a, is “adequate” and represents excellent value-for-money.

Pete



















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Ferguson Silver Member  Cape Coral, US  Nikonian since 20th Aug 2004 Thu 28-Mar-13 09:44 PM
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#23. "RE: Hypothesis - comments invited"
In response to Reply # 22





>Charts 4, 5 and 6 show a measurable difference between the AF times >as a function of the power source when using a 400mm f/2.8G lens.
>EN-EL15: 615mSec
>EH-5a: 515mSec
>Power2000: 625mSec

That's not exactly insignificant though. In .1 seconds the ball goes from on the tip of the person's fingers to out of the frame in basketball.

Two questions:

- How repeatable was it?
- Did you the release mode set to Focus?

I wish you were nearby, would love to know how the D4 compared.

I also think it might be interesting to compare to some other lens types, e.g. screw type, or something like the 50/1.4 which has a lot of travel as it focuses.

And while you have your lab set up, if you are still satisfying curiosity, see how VR being turned on affects the same timing. And power.



Linwood

Comments welcomed on pictures: Http://captivephotons.com

  

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PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014   Lincoln, US  Nikonian since 04th Jan 2010 Thu 28-Mar-13 10:25 PM
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#24. "RE: Hypothesis - comments invited"
In response to Reply # 23
Thu 28-Mar-13 11:17 PM by PeterBeckett


Hi Linwood,
I made a whole bunch of measurements other than those illustrated. I did, in fact, look into the effects of VR - but I don't have any means of introducing "vibration" in any repeatable manner. Got any ideas? I'd like to measure the effect that VR has on current draw!

Were results repeatable? Yes, within a few percent for all the AF measurements. Yes, I set release priority to "focus" for all such measurements. I repeated most measurements - and showed the most representative chart for the configuration.

Apart from the lenses whose results I used, I also made measurements with a 24-120mm f/4. Although a bit slower than the 70-200, there was nothing worth reporting. I have several other AF lenses including just a couple of "screwdriver" types (the 50mm f/1.5D and the 60mm Micro). Do you think it's worth evaluating AF with these?

A couple of comments that I didn't make in the "report":
AF is a WHOLE LOT faster when the focus does NOT start from the opposite end of the scale!

My interpretation is that Nikon uses brushless technology for ALL motors involved in AF, mirror positioning and shutter retensioning. The speed of such motors is controlled by the timing of currents flowing in multiple coils. Their torque, however, is likely to be affected by power supply voltage. Therefore, the ability to operate at full speed while under load may well be affected by the power source's capability to maintain voltage during high surge currents. I believe this last point is illustrated by the timing achieved with the three different power sources with the 400mm lens. It might be a larger effect with other "big" lenses in which the components that have to be moved during focusing, might be relatively "massive".

Yes, I AM still curious about this topic and others which could be investigated using the bits-and-pieces that I've assembled recently to support "this" investigation...

Pete

  

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AMusingFool Silver Member  Arlington, US  Nikonian since 30th Dec 2012 Thu 28-Mar-13 11:13 PM
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#25. "RE: Hypothesis - comments invited"
In response to Reply # 24



Thanks for doing this. Very interesting. And I wish you were closer, I'd love to see D4 results also.

"Geeks of All Nations, Compile!"
Visit my Nikonians gallery.

  

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PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014   Lincoln, US  Nikonian since 04th Jan 2010 Thu 28-Mar-13 11:19 PM
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#27. "RE: Hypothesis - comments invited"
In response to Reply # 25




Thanks David.

I'm almost tempted to get another D4. It was really good for some fast-paced wildlife shots!

Pete

  

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Ferguson Silver Member  Cape Coral, US  Nikonian since 20th Aug 2004 Thu 28-Mar-13 11:18 PM
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#26. "RE: Hypothesis - comments invited"
In response to Reply # 24



> I have several
>other AF lenses including just a couple of
>"screwdriver" types (the 50mm f/1.5D and the 60mm
>Micro). Do you think it's worth evaluating AF with these?

I have no practical need to know, but a mild curiosity is switching to the internal motor helped power draw. But it might be hard to tell without a comparable lens, one screw and one not.

Do you think the AC supply is similar to what the grip + D4 battery would do? I've been thinking about that just for battery compatibility, but the cost (grip + batteries + slide-in) is pretty high. Finding out I could get a tenth of a second on focus speed on some lenses might push me over the edge (though it sounds like it's unlikely on the ones that matter most to me, e.g. the 70-200 or 24-70, though a 200mm might be vaguely similar to the 400).

>> I did, in fact, look into the effects of VR - but I don't
>>have any means of introducing "vibration" in any repeatable
>> manner. Got any ideas? I'd like to measure the effect
>> that VR has on current draw!

I was more curious (as I think about this) whether there's a delay in the shutter from VR activation. "Spin up" (I have no idea if it actually spins). So if one does a grab shot with VR on does it shoot significantly slower than if VR is off? Whether or not there's vibration, no idea if that matters. If you think it does, could be as simple as putting your test setup on your washing machine?

Linwood

Comments welcomed on pictures: Http://captivephotons.com

  

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PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014   Lincoln, US  Nikonian since 04th Jan 2010 Thu 28-Mar-13 11:28 PM
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#28. "RE: Hypothesis - comments invited"
In response to Reply # 26



Hi Linwood,
LOL (I honestly did)! I just LOVE the washing M/C idea!!!

Lemme think about this for a bit.

Wouldn't it be great to actually know what's inside these lenses and bodies - rather than having to guess?

All the very best,

Pete
Hey, I don't have any problem with the concept of pursuing knowledge-for-the-sake-of-it!

  

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kendo1   UK  Registered since 19th Dec 2012 Fri 29-Mar-13 11:38 PM
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#29. "RE: Hypothesis - comments invited"
In response to Reply # 28



Autofocus speed.

I'd say,' Why would you want to?'

But there again, I'm in to landscape- it doesn't move very quickly.
I also like old MF glass.

Ken

  

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Ferguson Silver Member  Cape Coral, US  Nikonian since 20th Aug 2004 Sat 30-Mar-13 02:04 AM
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#30. "RE: Hypothesis - comments invited"
In response to Reply # 29




>I also like old MF glass.
>
>Ken

Be careful, he might hook the shunt and AC adapter up to you, to find out if you focus faster with more power.


Linwood

Comments welcomed on pictures: Http://captivephotons.com

  

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PeterBeckett Gold Member Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014   Lincoln, US  Nikonian since 04th Jan 2010 Sat 30-Mar-13 02:55 AM
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#31. "RE: Hypothesis - comments invited"
In response to Reply # 30




LOL!

I'm always looking for new projects...

Pete

  

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