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Subject: "Two CLS questions" Previous topic | Next topic
Toby01 Silver Member Nikonian since 19th Nov 2012Fri 09-Aug-13 03:33 AM
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"Two CLS questions"


El Sobrante, US
          

Hi, Everybody. I have two questions about Nikon's CLS system, even though I have been using it occasionally for several years:

1) My SB700 does not support normal TTL; it only does TTL-BL. If I use the SB700 as the master and a mix of other Nikon strobes for illumination, does CLS work in normal TTL or does the camera meter the flash in TTL-BL mode?

2) I have read many times that you should not use auto-ISO with TTL flash, and I basically understand the reasons for this. Normally, I use flash with the camera in manual, underexpose the ambient by 1/3 to 1 stop, and use the flash with +1/3 to +1 EC to bring exposure to the 'normal metered' value. But I wondered whether I could use auto-ISO with flash to handle situations where the ambient light is changing quickly. Here is my idea: in manual exposure mode, set my aperture and shutter speed as desired, set the camera EC to -1/3 to -1 and use auto-ISO to get the ambient underexposed by the corresponding amount. Then have the flash EC set to offset the camera's underexposure. Would this work? If not, can you explain why not? I will try some experiments, but I'm not sure how accurately I will be able to evaluate the results, particularly if this scenario works variably depending on the environment.

Thanks.

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Replies to this topic
Subject Author Message Date ID
Reply message RE: Two CLS questions
ScottChapin Moderator
09th Aug 2013
1
Reply message RE: Two CLS questions
Toby01 Silver Member
09th Aug 2013
2
     Reply message RE: Two CLS questions
ScottChapin Moderator
09th Aug 2013
3
Reply message RE: Two CLS questions
Toby01 Silver Member
09th Aug 2013
4
Reply message RE: Two CLS questions
mklass Platinum Member
10th Aug 2013
5
Reply message RE: Two CLS questions
Vlad_IT Silver Member
11th Aug 2013
6
Reply message RE: Two CLS questions
mklass Platinum Member
11th Aug 2013
7
Reply message RE: Two CLS questions
Toby01 Silver Member
11th Aug 2013
8
     Reply message RE: Two CLS questions
Vlad_IT Silver Member
11th Aug 2013
9
Reply message RE: Two CLS questions
Toby01 Silver Member
13th Aug 2013
10
Reply message RE: Two CLS questions
ScottChapin Moderator
13th Aug 2013
11
Reply message RE: Two CLS questions
Vlad_IT Silver Member
13th Aug 2013
12
Reply message RE: Two CLS questions
Toby01 Silver Member
15th Aug 2013
13

ScottChapin Moderator Awarded for his high level skills in various areas, including Aviation and Birds Photography Charter MemberFri 09-Aug-13 03:21 PM
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#1. "RE: Two CLS questions"
In response to Reply # 0


Powder Springs, US
          

CLS and CTL work only in TTL. TTL-BL is for solo on camera flash.

Scott Chapin
Powder Springs, GA, USA
Nikonians Team Member

  

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Toby01 Silver Member Nikonian since 19th Nov 2012Fri 09-Aug-13 04:52 PM
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#2. "RE: Two CLS questions"
In response to Reply # 1


El Sobrante, US
          

Thanks for that info, Scott. Do you have any idea about my second question?

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ScottChapin Moderator Awarded for his high level skills in various areas, including Aviation and Birds Photography Charter MemberFri 09-Aug-13 09:38 PM
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#3. "RE: Two CLS questions"
In response to Reply # 2


Powder Springs, US
          

Sorry I didn't get to question two earlier. I was swamped at work, expecting others to chime in. Really, the big problem is not so much exposure control as it is noise control.

If you are willing to let the ISO climb and introduce noise even on the flash illuminated areas where you don't need to settle for noise, then go for it.

Obviously, if you're shooting a wedding, then you don't want noisy portraits. You just need to be aware of what's going on.

Scott Chapin
Powder Springs, GA, USA
Nikonians Team Member

  

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Toby01 Silver Member Nikonian since 19th Nov 2012Fri 09-Aug-13 11:11 PM
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#4. "RE: Two CLS questions"
In response to Reply # 0


El Sobrante, US
          

In addition to Scott's info, I wanted to provide the results of some experiments I just finished. There is a fundamental flaw in my original idea because of the way Nikon has implemented flash and auto-ISO. I found that they keep ramping up the flash component of the exposure, rather than increasing the ISO. I was hoping that the ISO would climb as the ambient light level fell, so that I could keep the flash contribution constant, but it doesn't work that way. I realize, as Scott points out, that I could run into noise issues if I didn't keep an eye on how far the ISO went up, but figured as long as the ambient didn't change by more than 3 stops I'd be OK. Oh, well, I'll just have to continue doing this the way I have for years, playing the balancing act between ISO, shutter speed, and aperture, all in manual mode.

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mklass Platinum Member As a semi-professional involved in all manner of photographic genres including portraiture, sports, commercial, and events coverage, Mick is always ready to help Nikonians by sharing his deep knowledge of photography and printing. Nikonian since 08th Dec 2006Sat 10-Aug-13 03:28 PM
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#5. "RE: Two CLS questions"
In response to Reply # 0


Tacoma, US
          

The SB-700 uses TTL-BL when your camera is set to Matrix metering. Switch to Center or Spot metering and it will switch to TTL.

Mick
http://www.mickklassphoto.com
or
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Vlad_IT Silver Member Nikonian since 21st Sep 2011Sun 11-Aug-13 05:52 AM
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#6. "RE: Two CLS questions"
In response to Reply # 0
Sun 11-Aug-13 06:07 AM by Vlad_IT

New Tampa, US
          

>Hi, Everybody. I have two questions about Nikon's CLS system,
>even though I have been using it occasionally for several
>years:
>
>1) My SB700 does not support normal TTL; it only does TTL-BL.
>If I use the SB700 as the master and a mix of other Nikon
>strobes for illumination, does CLS work in normal TTL or does
>the camera meter the flash in TTL-BL mode?
>





Use spot metering to switch to TTL mode







>2) I have read many times that you should not use auto-ISO
>with TTL flash, and I basically understand the reasons for
>this. Normally, I use flash with the camera in manual,
>underexpose the ambient by 1/3 to 1 stop, and use the flash
>with +1/3 to +1 EC to bring exposure to the 'normal metered'
>value. But I wondered whether I could use auto-ISO with flash
>to handle situations where the ambient light is changing
>quickly. Here is my idea: in manual exposure mode, set my
>aperture and shutter speed as desired, set the camera EC to
>-1/3 to -1 and use auto-ISO to get the ambient underexposed by
>the corresponding amount. Then have the flash EC set to offset
>the camera's underexposure. Would this work? If not, can you
>explain why not? I will try some experiments, but I'm not sure
>how accurately I will be able to evaluate the results,
>particularly if this scenario works variably depending on the
>environment.
>
>Thanks.
>
>


I can speak only about D7000 camera. in Auto-ISO mode camera is metering ambient light and sets the lowest allowed shutter speed, if the subject is still underexposed, than camera bumps ISO up. the same rule is for camera with Speedlight attached. in most cases we use speadlights when the ambient light is very low. so camera will bump ISO all way up to the max allowed auto ISO value and only then will calculated required flash power using reflection data from a pre-flash, but calculation already includes ISO chosen by the camera.

Now, I use Speedlight a lot in sunny weather to brighten the shadows, or in cloudy weather to make a main subject to stand out a bit out of dull environment. in all situations when the ambient light is the main light - you most of the time need to use TTL-BL mode (and not TTL). And in such situations I use auto ISO from 100 to 800.

In a dark environment, when flash is the main power source plain TTL mode (combined with manual exposure mode on your camera will give you the most consistent results.

The bottom line I keep ISO at 800 in most cases when using a speedlight or if I swith to auto ISO mode - I keep max value to 800

I have such settings programmed in to U1. with spot metering (for regular TTL mode) and camera exposure set to M(annual) mode.

I hope it help as a start point for your research.



in the example below I used a manual mode to set aperture and shutter speed to correctly expose outside environment with slight +1/2 stop over-exposure. Than I used speedlight in TTL mode (metering was set to spot, regardless using manual aperture and shutter speed) and turned the flash head 60 degrees up and to the left of me for bounced photography. TTL mode correctly exposed my lovely wife, without harsh shadows or bright flash reflections in the glass.

  

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mklass Platinum Member As a semi-professional involved in all manner of photographic genres including portraiture, sports, commercial, and events coverage, Mick is always ready to help Nikonians by sharing his deep knowledge of photography and printing. Nikonian since 08th Dec 2006Sun 11-Aug-13 11:53 AM
5572 posts Share on Facebook Share on Twitter Share on Linkedin    Click to send email to this author Click to send private message to this authorClick to view this author's profile
#7. "RE: Two CLS questions"
In response to Reply # 6


Tacoma, US
          

Good example, Vlad.

Mick
http://www.mickklassphoto.com
or
Visit my nikonians gallery

  

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Toby01 Silver Member Nikonian since 19th Nov 2012Sun 11-Aug-13 04:11 PM
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#8. "RE: Two CLS questions"
In response to Reply # 6


El Sobrante, US
          

Thanks for the info, Vlad. I was hoping that the auto-ISO/flash combination worked as you have described, but in my brief testing it didn't seem to. I will try again, with a little more rigor to my methodology. I'm trying all this with the on-camera flash as the master in a CLS setup, with the on-camera flash set to contribute nothing to the exposure.

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Vlad_IT Silver Member Nikonian since 21st Sep 2011Sun 11-Aug-13 07:07 PM
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#9. "RE: Two CLS questions"
In response to Reply # 8
Sun 11-Aug-13 07:26 PM by Vlad_IT

New Tampa, US
          

>Thanks for the info, Vlad. I was hoping that the
>auto-ISO/flash combination worked as you have described, but
>in my brief testing it didn't seem to. I will try again, with
>a little more rigor to my methodology. I'm trying all this
>with the on-camera flash as the master in a CLS setup, with
>the on-camera flash set to contribute nothing to the
>exposure.


I came last nigh from a party and must be did not understand your problem. I'm not big on CLS, but I have the basic knowledge and the principals are the same as you would use only one flash - with CLS the system does as many pre-flashes as you have groups set up.

I also know that Nikon's CLS is not an "intelligent" to recognize the situation when you set three groups of speedlights to light the same main object - you most likely overexpose it. Nikon had in mind that each group will cover a different part of frame.

start from basics. metering on camera set to spot, to enable regular TTL, than set camera to manual exposure and experiment with different exposure compensation for each group. when you'll get desire result - start introducing the other factors, like matrix metering. And the last I would introduce is the auto ISO.


as per your idea in question #2:

TTL and TTL-BL works differently. in TTL-BL camera calculates the correct flash output MOSTLY based on distance information from lens's CPU. Pre-flash information is used to set white balance only. The distance to the object is the main factor. And that's why TTL-BL is to be used when ambient light is the main source of light.

try this. take a picture of the main object in sufficient ambient light indoors in matrix metering mode (just make sure the object is far away from the back wall as possible) - your object should be correctly exposed along with other parts of the room. Now switch the lens in manual focusing mode and put focus to infinity and slightly move the focus ring back. in such situation your main object will be overexposed, as the flash power will be increased to cover greater distance.

in TTL mode camera calculates flash power based on pre-flash information in the center of the frame, regardless the distance to the object.

That's the main reason to use regular TTL mode when flash is the main source of light - we don't want to balance the flash output with the ambient light, whish is very dark, especially when auto ISO is used. and in any case when using flash the auto ISO should be restricted to some number, like 800 or 1600. I keep it caped at 800. and the reason is in most cases if auto ISO needs to bump ISO above 800 - that means that ambient light is not sufficient to be a main light and TTL should be used instead of TTL-BL.

you should control the camera and not vise versa.
here is an example of TTL mode with ISO set to 25,600. I had to remove noise in PP and do some sharpening, but the result is very pleasing:



Best regards,
Vlad

  

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Toby01 Silver Member Nikonian since 19th Nov 2012Tue 13-Aug-13 06:37 PM
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#10. "RE: Two CLS questions"
In response to Reply # 0


El Sobrante, US
          

Thanks for all of the earlier replies. I have done a series of tests using all combinations of my D90, D7100, SB700, and SB900, and have found some interesting aspects related to my original questions. Both of the cameras work the same way with both of the flashes, with the exception of the SB700 using normal TTL only when the cameras are in spot metering mode. Here are my results:

1) I confirmed Scott's statement that TTL-BL only works when the flash is mounted on the camera. Even with the SB700, which does not have a switch position for TTL, mounted on the camera and the metering mode set to matrix, TTL will be the result in a CLS setup.

2) If the flash is on-camera, auto-ISO will adjust the ISO, but it is unpredictable in how much it will change. At least, I haven't been able to figure out how much it will change the ISO vs upping the flash power in any given circumstance.

3) CLS use disables auto-ISO, even though auto-ISO will still show on the upper LCD and in the finder. In other words, if you have, for example, an SB900 mounted on the camera and you move the on/off switch on the flash to master, ISO will drop to the last ISO you specified manually.

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ScottChapin Moderator Awarded for his high level skills in various areas, including Aviation and Birds Photography Charter MemberTue 13-Aug-13 07:43 PM
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#11. "RE: Two CLS questions"
In response to Reply # 10


Powder Springs, US
          

I've never paid attention to number 3. Though with multiple flash I have never used auto ISO. It makes sense in a studio like situation with all the lights that auto ISO might not be necessary or desirable.

Scott Chapin
Powder Springs, GA, USA
Nikonians Team Member

  

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Vlad_IT Silver Member Nikonian since 21st Sep 2011Tue 13-Aug-13 08:38 PM
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#12. "RE: Two CLS questions"
In response to Reply # 10


New Tampa, US
          

>3) CLS use disables auto-ISO, even though auto-ISO will still
>show on the upper LCD and in the finder. In other words, if
>you have, for example, an SB900 mounted on the camera and you
>move the on/off switch on the flash to master, ISO will drop
>to the last ISO you specified manually.


Nice to know! thanks a lot.
Best regards,
Vlad

  

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Toby01 Silver Member Nikonian since 19th Nov 2012Thu 15-Aug-13 04:11 AM
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#13. "RE: Two CLS questions"
In response to Reply # 0


El Sobrante, US
          

Just one more comment, although it doesn't actually relate to CLS usage: I found that putting the on-camera flash in manual mode, which I have done in the past to trigger simple optical slaves, will also disable auto-ISO. This one puzzles me a little, but I guess Nikon figures that if you have the flash in manual, you don't want any automation helping you out.

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