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Focus Problems Continue -- Your Insight Requested


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johno

St. Louis, US
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johno Silver Member Nikonian since 23rd May 2006
Fri 30-Nov-12 06:50 PM

All,

After two trips to Nikon to fix the left focus issue between July and October the camera is focusing worse than ever. (There was a delay between trip one and trip two while Nikon Japan pondered the situation. For me, the story that this problem is fixed is not proving true.

I have uploaded samples to Osthus.us/focus_test.

If you decide to have a look and help me out with your insights, you will find a big zip with about 20 images. I have also uploaded a few sample JPEGs of some of the worst examples for anybody who does not want to download the big file to see the test series.

Test conditions: Tripod mounted. High shutter speed. Defocus then focus via left, center then right sensors. The photos of my 85 mm 1.4 were hand-held.

In the zip file you will see a couple of series of 3 shots where the target (mailbox) is centered in each of the three images. What I did there is shoot left-sensor focus, lock and re-center, center sensor; then right sensor focus, lock and recenter. This was done to give me three shots with the target centered. For good measure I simply shot left, center and right sensor images of the same target.

What I see:

-There is variation in focus across all sensors
- The image sets where all three shots were framed the same show a large variation in file size. In some cases as much as 2 MB with the SAME SHOT.

I also tied normal shots like focusing on a red barn isolated against a blue sky; and the D800 could not reliably hit the side of the barn.

I would be grateful your insights. Do I really have a focus problem or am I imagining this?

Thanks,

John

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rplst8

Johnstown, US
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#1. "RE: Focus Problems Continue -- Your Insight Requested" | In response to Reply # 0

rplst8 Silver Member Nikonian since 18th Dec 2008
Fri 30-Nov-12 06:17 PM | edited Fri 30-Nov-12 06:17 PM by rplst8

>In the zip file you will see a couple of series of 3 shots
>where the target (mailbox) is centered in each of the three
>images. What I did there is shoot left-sensor focus, lock and
> re-center, center sensor; then right sensor focus, lock and
>recenter. This was done to give me three shots with the
>target centered. For good measure I simply shot left, center
>and right sensor images of the same target.
>
>I would be grateful your insights. Do I really have a focus
>problem or am I imagining this?

I haven't looked at your images, however I can tell you now that any comparison of a focused and recomposed image with one shot via the center sensor is invalid.

You can't focus and recompose to do any focus point to focus point comparison.

--
RL

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johno

St. Louis, US
525 posts

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#2. "RE: Focus Problems Continue -- Your Insight Requested" | In response to Reply # 1

johno Silver Member Nikonian since 23rd May 2006
Fri 30-Nov-12 08:15 PM | edited Fri 30-Nov-12 08:16 PM by johno

OK

Anticipating methodology pushback I shot some the other way. So at least some of my "tests" may be valid. Or more valid.

In any case, images are in fact out of focus. My presumpumption is that if a camera is functioning correct a comparison would become irrelevant, because all of the shots would be in focus.

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johno

St. Louis, US
525 posts

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#3. "RE: Focus Problems Continue -- Your Insight Requested" | In response to Reply # 2

johno Silver Member Nikonian since 23rd May 2006
Mon 03-Dec-12 03:09 AM

I spent some time just shooting around a trendy street with my daughter. Enough with "testing"

The walking around shots were fuzzy too, more so with the 24 70 than the 105 2.8. Wich made me think that's really odd.

So I broke out a ruler at home and tried some shots and sure enough it is front focusing like crazy. I tried the fine tune settings but I maxed out the 24-70 with the focus point still 2 inches too close.

The 105 got within an inch of the target at plus 15 and I gave up to go for a bike ride.

This raises a question about my second trip for the left focus fix. What the >#!|%%{. Really, there is no way that anybody could have really checked this camera and pronounced it shooting on target. Unless their test lens is coincidentally -15.

I have several other lenses left to test. But I am seeing a trend toward severe fron focus.

Is this the sort of thing that could be fixed by a competent technician? I do not mean at Nikon. I'm going to just pay somebody to fix it.


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briantilley

Paignton, UK
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#4. "RE: Focus Problems Continue -- Your Insight Requested" | In response to Reply # 3

briantilley Gold Member Deep knowledge of bodies and lens; high level photography skills Donor Ribbon awarded for his support to the Fundraising Campaign 2014 Nikonian since 26th Jan 2003
Mon 03-Dec-12 07:21 AM

>Is this the sort of thing that could be fixed by a competent
>technician?

Without some more data, we can't advise you either way. Which AF mode, AF-area mode, AF point(s), aperture, shutter speed, etc...

I doubt whether many members will be inclined to view even the JPEG's you posted, as they are 13MB each. Try posting smaller versions (perhaps in your gallery here) - we will still be able to see any big problems that exist.

If the ruler was used at an angle to the sensor as an AF target, the results mean virtually nothing. Only when a flat target is used, parallel to the sensor, can you be absolutely sure about what the camera thinks it's focusing on.

Brian
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johno

St. Louis, US
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#5. "RE: Focus Problems Continue -- Your Insight Requested" | In response to Reply # 4

johno Silver Member Nikonian since 23rd May 2006
Mon 03-Dec-12 12:39 PM | edited Mon 03-Dec-12 12:43 PM by johno

This is frustrating and I am mostly disappointed in myself. The images are out of focus. What f stop and shutter speed are required to test a D800 for focus accuracy? On a tripod with a 2 second exposure delay?

I tried the flat target scenario at the request of a famous Nikon blogger and I was told I did that wrong too. But I felt less bad after hearing that 40 percent of the people who followed the "Smith" protocol also were incapable of a proper flat-target test.

It is in fact possible to discern a camera problem without a certain test condition. To claim otherwise is to say the camera can work properly only under that condition. If I posted shots praising the camera showing the images in focus would you also say I have not proved the case given there was no flat target?

I'm now 100 percent satisfied that there is a problem. I've tried shooting under various conditions and see the same result. The focus offset is reduced with focus fine tune. Reliably. That I was so insecure I needed help to tell me that my camera was malfunctioning is a bigger problem than the camera.

P.S. in review mode and in Nikon software the focus point can be seen, so it is in fact possible to determine what the camera thinks it is focusing on in the absence of a flat target. It also states the focus distance.

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briantilley

Paignton, UK
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#6. "RE: Focus Problems Continue -- Your Insight Requested" | In response to Reply # 5

briantilley Gold Member Deep knowledge of bodies and lens; high level photography skills Donor Ribbon awarded for his support to the Fundraising Campaign 2014 Nikonian since 26th Jan 2003
Mon 03-Dec-12 01:21 PM

>I'm now 100 percent satisfied that there is a problem.

If you're convinced, then by all means proceed to have it fixed. I hope it is successful.

But here's what I'm getting at - if you are trying to convince people here there is a problem, or want practical advice on what to do about it, you need to give us some better material to work with

>P.S. in review mode and in Nikon software the focus point can
>be seen, so it is in fact possible to determine what the
>camera thinks it is focusing on in the absence of a flat
>target.

The problem there is that the actual AF sensors do not match up exactly with the displayed focus brackets - in particular, the AF sensor is typically larger than the markings. With an angled target, there will be detail at different distances under the same sensor, which leads to unpredictable results. A flat, parallel target eliminates this variable.

Brian
Welsh Nikonian

johno

St. Louis, US
525 posts

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#7. "RE: Focus Problems Continue -- Your Insight Requested" | In response to Reply # 6

johno Silver Member Nikonian since 23rd May 2006
Mon 03-Dec-12 01:54 PM

Thanks for your replies.

I just did some shooting outside to try the fine-tune-on vs. fine-tune-off settings using the +20 I dialed into the 24-70.

Night and day difference. No ambiguity.

I will be uploading some small images so anybody who wants to see the effect of autofocus fine tune can see it. I had zero interst in autofocus fine tune until now. In my case it is a very big differnce.

The system is misnamed. It should be called the "focus accuracy verification" setting. Or, "self-service quality control and tech support" setting.

Your note to "have it fixed" is my hope too. Whether Nikon can accomplish that is in doubt.

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KnightPhoto

Alberta, CA
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#8. "RE: Focus Problems Continue -- Your Insight Requested" | In response to Reply # 0

KnightPhoto Gold Member Nikonian since 18th Dec 2006
Thu 06-Dec-12 03:16 AM | edited Thu 06-Dec-12 03:36 AM by KnightPhoto

I haven't looked at your test photos yet but this comment drew my attention:

"What I see:
-There is variation in focus across all sensors
- The image sets where all three shots were framed the same show a large variation in file size. In some cases as much as 2 MB with the SAME SHOT."

With my newly purchased FocusTune software, the testing protocol calls for shooting 4 identical shots at each AF fine tune setting. The software then throws out outliers(!) and then proceeds to chart the variation, with those values showing the best average result being the suggested AF fine tune value. What is my point? We can expect variation in PDAF result from shot to shot, even on a locked down tripod under identical condition.

Also you ask about shutter speed, I try and get at least 1/250 with 3 second delay timer. I had to buy a 500 watt construction light to actually achieve this. This is on a locked down 5-series Gitzo. I've got enough variables to deal with without adding camera vibration into the mix. The job is about eliminating variables.

Anyhow if +20 is consistently needed, yes your camera is way out of whack. Your remaining problem doesn't sound like the left AF problem, at least not the way you are describing it, though that may be what you started with.

It might be helpful to just post the real-world images. We can check for motion blur vs. focus or possible suggestions for technique changes.

Edit: I looked at some photos on your website. It's hard to tell and not even sure I was looking at the right photos. It's too bad we can't reach out and shoot your camera and form some conclusions The mailbox ones (with house/garage in background) strike me as too small an AF target. I.e. On the shots where the mailbox is blurry, it looks like the AF grabbed onto the garage door way way back in the background, so the mailbox ones don't look indicative of anything to me. Nice looking neighbourhood BTW!

Make sure you look for consistent patterns. Then you know you need to AF tune. Sorry, not much help.

Best regards, SteveK

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johno

St. Louis, US
525 posts

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#9. "RE: Focus Problems Continue -- Your Insight Requested" | In response to Reply # 8

johno Silver Member Nikonian since 23rd May 2006
Thu 06-Dec-12 04:24 AM

Thank you for the time and thought you out into helping me.

I started another thread with a few samples of the before and after fine tune results.

I've given up on test shots. But your software sounds really handy. I would like to have that capability. Too bad we need it.

And you are also right..why shoot a mailbox anyway. The samples I posted in the other thread include a few targets that are equally unrealistic, but they show the before and after pretty clear.

Now that I've isolated the symptoms to a repeatable front focus problem, the next step is figuring out how it got that way during repair number 2, why the doctor made the patient worse, and what can be done to fix it.

I'd be grateful if you'd drop into the other thread and have a look. Now that the problem is isolated I'm hoping there will be some discussion over there.

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briantilley

Paignton, UK
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#10. "RE: Focus Problems Continue -- Your Insight Requested" | In response to Reply # 0

briantilley Gold Member Deep knowledge of bodies and lens; high level photography skills Donor Ribbon awarded for his support to the Fundraising Campaign 2014 Nikonian since 26th Jan 2003
Thu 06-Dec-12 07:06 AM

To avoid duplication, further replies may be posted in John's new thread.

Thanks!

Brian
Welsh Nikonian

G