Nikon CLS and i-TTL discussion

wildviper

Mod edit: This is a discussion moved from this starting thread in the Accessories forum:

http://dgrin.com/showthread.php?t=198368

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ziggy53 wrote: »

when you use a lens which supplies distance information, the E-TTL II program automation puts extra emphasis on the guide number of the flash and the distance to subject. The flash does not know about any modifier and it will "not completely" compensate for light loss incurred by a flash modifier.

I guess this one more reason to think again before using 3rd party lenses. I am not sure they are as sophisticated as Nikons or Canon's lenses.

Ziggy, can you clarify your comment about flash not compensating for the diffuser? Is that true only on Canons? Cause I have heard Joe Mcnally on numerous times say that the system is smart enough to figure all this out since it reads the "amount" of light reflected back into the lens. ???

If you tilt the flash or swivel the flash, the flash program, should revert to basic E-TTL which does not use distance information.

Once again, is this related to Canon cameras only? I didn't realize the Nikon's version of E-TTL II ..."i-TTL something or the other" had this issue? Thanx

ziggy53

wildviper wrote: »

ziggy53 wrote: »

when you use a lens which supplies distance information, the E-TTL II program automation puts extra emphasis on the guide number of the flash and the distance to subject. The flash does not know about any modifier and it will "not completely" compensate for light loss incurred by a flash modifier.

I guess this one more reason to think again before using 3rd party lenses. I am not sure they are as sophisticated as Nikons or Canon's lenses.

Ziggy, can you clarify your comment about flash not compensating for the diffuser? Is that true only on Canons? Cause I have heard Joe Mcnally on numerous times say that the system is smart enough to figure all this out since it reads the "amount" of light reflected back into the lens. ???

Some Canon lenses also lack distance information. I am not sure where there might be a comprehensive listing of lenses that have distance information.

Please reread my post. I have emphasized the important portions. The E-TTL II does not ignore the TTL component of flash automation but it does put primary flash exposure emphasis on the guide number and distance calculation. The more a flash modifier negatively affects the flash's output, the more you will see underexposure.

Both the exposure mode and the metering program will impact the calculations. I tend to use Aperture priority mode and Evaluative/Matrix metering myself, with some Manual mode thrown in.

I would have to see Joe's comments before I could comment on what he said.

wildviper wrote: »

ziggy53 wrote: »

If you tilt the flash or swivel the flash, the flash program, should revert to basic E-TTL which does not use distance information.

Once again, is this related to Canon cameras only? I didn't realize the Nikon's version of E-TTL II ..."i-TTL something or the other" had this issue? Thanx

I do believe that Nikon was the innovator of using guide number/distance information in their i-TTL. I am less sure of the exact implications. Since no flash can know the distance from flash to subject in the case of bounced flash I believe that a Nikon flash only allows i-TTL in flash forward position and they revert to Nikon TTL in bounce orientation. Yes, Nikon i-TTL should also be affected by a flash modifier used in forward orientation. I don't know how their exposure and metering modes are affected in any detail.

Check out Pathfinder's sources for Canon E-TTL II information:

http://www.dgrin.com/showthread.php?t=70330&highlight=fill+flash+pathfinder

If we want to pursue the technical aspects any more it would be best to open a thread in the Techniques forum.

wildviper

Here is one clip I found...albeit its the girl that says so vs. Joe in this one. I have other videos and I will have search those.

Video link
Go to 9:20 marker.

ziggy53

wildviper wrote: »

Here is one clip I found...albeit its the girl that says so vs. Joe in this one. I have other videos and I will have search those.

Video link
Go to 9:20 marker.

The video in your link is of a desert shoot with three subjects, individually and as a group portrait. I don't find any mention of the lighting situation at 9:20 but all of these are multi-light setups and, it would appear, that while the external flash on the camera is used as "commander/master", it does not appear to be used as "key" light in any of the setups. Indeed the key light in the 2 strobe show-girl shot appears to be camera left and the key light flash does not appear to have a modifier on the flash head.

If the Nikon CLS is using the flash from the key light to set primary flash contribution exposure, as it should, and if the subordinate flashes are set at ratios relative to the key, that explains the proper exposure without flash exposure compensation.

Edit: I should mention that in a multi-flash lighting setup the system would not be in Nikon i-TTL mode. The reason is that the system cannot know the distance from flash to subject to use the guide-number/distance calculation. Rather it falls back to Nikon TTL.

wildviper

Ziggy,

Don't try and take it that I am trying to argue for the heck of it. What you are saying is not what I have been led to believe (various legitimate sources). With my understanding, what the OP is trying to do should work the same with a Nikon system. I do not know the Canon system and so is not a knock on that.

At the video marker 9:20, you hear the lady say something to the effect of "The CLS system is smart enough to calculate correct flash output without hinderance from the diffusion material". Just by that statement, I take it to understand that the system figures out the reflected light coming back to the camera...then telling the flashes how much power to put out...thus if the diffusion material is using up a stop or two of light....the CLS system is aware and adjusts for this. No???

I am still trying to find publicly available videos where Joe has said something similar.

I know this may seem like a hijack of the OP's thread, but I think it is relevant. Let me know if otherwise.

basflt

diffusion material is using up a stop or two of light....the CLS system is aware and adjusts for this. No???

no

CLS only controls things like fast-sync and modeling flash , nothing else

the camera cannot ever know what diffuser you use
nor can it know the distance
so it does nothing

TTL cannot do that either
TTL only measures light and adjust amount of flash accordingly , nothing else
this is done before the shot , not after

ziggy53

wildviper wrote: »

Ziggy,

Don't try and take it that I am trying to argue for the heck of it. What you are saying is not what I have been led to believe (various legitimate sources). With my understanding, what the OP is trying to do should work the same with a Nikon system. I do not know the Canon system and so is not a knock on that.

At the video marker 9:20, you hear the lady say something to the effect of "The CLS system is smart enough to calculate correct flash output without hinderance from the diffusion material". Just by that statement, I take it to understand that the system figures out the reflected light coming back to the camera...then telling the flashes how much power to put out...thus if the diffusion material is using up a stop or two of light....the CLS system is aware and adjusts for this. No???

I am still trying to find publicly available videos where Joe has said something similar.

I know this may seem like a hijack of the OP's thread, but I think it is relevant. Let me know if otherwise.

No problem with this discussion. Nikon and Canon flash systems can get complicated in both nomenclature and function.

Let's start with the nomenclature. The Nikon CLS system is an abbreviation for "Creative Lighting System" and in the context of this discussion it refers to the wireless lighting control automation of a multi-flash setup. In a multi-flash setup i-TTL is not used because you cannot know the distance from the flash to the subject for each flash. In this case of a multi-flash setup the camera and flash revert to the slightly simpler Nikon TTL system of flash automation. (I suppose that i-TTL could be a component for the external flash if the external flash is the "key" light, but that's not my understanding of how the system works in a multi-flash/wireless/CLS operation.)

Especially when the key light is off-camera, the camera and flash coordinate to send a reference pre-flash pulse of light. This pulse is not used directly for imaging but it is used for measuring the scene and subject for illumination values. The results of the pre-flash are coordinated with the flash program with regard to channels, groups and ratios. Each flash is then sent the required flash output information and then each flash fires during the image exposure at this calculated output.

In a "single", camera mounted, external flash, Nikon i-TTL can be used because the camera and flash program can use distance information as the primary determinant of flash power for proper exposure. The distance information comes from a compatible lens capable of supplying the camera with its distance information after AF.

I believe that linked video is correct because the CLS/wireless is using Nikon TTL, which does use the camera's metering to help determine the correct flash outputs by measuring the pre-flash results.

It is not correct to think that CLS means Nikon i-TTL. Those are mostly exclusive technologies (although Nikon i-TTL does include "some" Nikon TTL information from a similar pre-flash cycle).

basflt

but that's not my understanding of how the system works in a multi-flash/wireless/CLS operation.

you are right , sir
it doesnt work , at least not properly

i dont think any brand of camera can automaticaly compensate for diffusers

thats why i set my flash to manual , just as all other things in my camera

ziggy53

Here is a link to a digram of the CLS multi-flash system, with pre-flash and primary flash pulses indicated.

Here is the primary discussion leading to the diagram:

http://photo.net/photography-lighting-equipment-techniques-forum/00JJUC

basflt

thanks for that ziggy53

going to experiment again

Dan7312

In one of the experiments I did with my 7D\580EXII on camera combo, I used FEL (Flash Exposure Lock, on Canon that means I press a button to tell the camera to evaluate the scene illumination which it does by using the pre-flash).

When i use FEL the image produced by the flash has the same brightness with or without the Lastolite modifier on the flash. So with FEL the camera is compensating for the light loss of the modifier.

When I don't use FEL the images taken with the modifier on the flash are about 2-3 stops darker then when no modifier is on the flash. So it looks like in this case the camera is setting the flash level mainly based on distance. I say mainly because the preflash does occur so I'm guessing it does take some part in the calculation, but much less so than when FEL is used.

basflt wrote: »

you are right , sir
it doesnt work , at least not properly

i dont think any brand of camera can automaticaly compensate for diffusers

thats why i set my flash to manual , just as all other things in my camera

wildviper

basflt wrote: »

i dont think any brand of camera can automaticaly compensate for diffusers

thats why i set my flash to manual , just as all other things in my camera

Even after reading what Ziggy and you say, I am not fully convinced. I probably am guilty of interchanging the words to describe one technology vs. another...but, basicly, this is what I am saying:

The Nikon flash system (CLS , iTTL or TTL) does adjust for diffusers. Its not about it knowing what diffuser it is..it is about the "amount" of light reflected back(during the pre-flashes and exposure calculations) to the camera and the camera adjusting the output before it "fires" the flashes.

And that is what that lady is saying in the Nikon video.

Once again, I am not sure how it does all this....but here is another link:

What is Nikon i-TTL?

The above link pretty much says what I am saying....it doesn't matter if you put a diffuser infront of this flash or are bouncing the light off or direct flash...the system apparently figures all this out via the amount of reflected light coming back to the camera...then adjusts it accordingly.


The above is what I have been led to believe...now are you going to continue to tell me there is no Santa?????? :cry

I know we will get to the bottom of this sooner than later. :P Or at least I will! haha

ziggy53

wildviper wrote: »

Even after reading what Ziggy and you say, I am not fully convinced. I probably am guilty of interchanging the words to describe one technology vs. another...but, basicly, this is what I am saying:

The Nikon flash system (CLS , iTTL or TTL) does adjust for diffusers. Its not about it knowing what diffuser it is..it is about the "amount" of light reflected back(during the pre-flashes and exposure calculations) to the camera and the camera adjusting the output before it "fires" the flashes.

And that is what that lady is saying in the Nikon video.

Once again, I am not sure how it does all this....but here is another link:

What is Nikon i-TTL?

The above link pretty much says what I am saying....it doesn't matter if you put a diffuser infront of this flash or are bouncing the light off or direct flash...the system apparently figures all this out via the amount of reflected light coming back to the camera...then adjusts it accordingly.


The above is what I have been led to believe...now are you going to continue to tell me there is no Santa?????? :cry

I know we will get to the bottom of this sooner than later. :P Or at least I will! haha

The more I get into the Nikon system the more confusing some of the terms become. I still believe that I am correct in what I've told you so far. The European Nikon site has an elaboration on the different Nikon TTL flash technologies employed:

https://nikoneurope-en.custhelp.com/app/answers/detail/a_id/8443/~/guide-to-slr-ttl-flash-modes

Of what it says I think you need to only look at the:

3D Multi-Sensor balanced fill-flash
and
Multi-Sensor balanced fill-flash

... because according to:

The Nikon compatibility chart

"and" the

Features table for the SB600 flash, only the "TTL Balanced fill" is available on your cameras (the D70s and the D300s). (i.e. of the other 2 modes mentioned, "Standard TTL flash" is for film cameras and "Matrix balanced fill-flash" applies to very old cameras like the Nikon D1/D100 [which lack the "3D" metering program of more recent cameras], I believe.)

Of the two flash metering automation modes, "3D Multi-Sensor balanced fill-flash" and "Multi-Sensor balanced fill-flash", they differ only in the allowed use of distance information. If the distance information is available from the lens, a type "D" or type "G" lens, then "3D Multi-Sensor balanced fill-flash" is used. If distance information is not available, as in a non-D/G lens or when the flash head is not straight forward, then the simpler "Multi-Sensor balanced fill-flash" is used.

If Nikon does not discriminate the label of i-TTL for these applications then you are right for the simpler "Multi-Sensor balanced fill-flash" in that it is still i-TTL. (I could swear that I read a Nikon publication describing i-TTL as the more complicated "3D Multi-Sensor balanced fill-flash" and calling the simpler mode "Nikon TTL" or somesuch. I can't find that information now and the information I can find, that I linked above, labels both modes as i-TTL.)

At any rate, I do think that you need to determine for yourself the relationship between the more complicated "3D Multi-Sensor balanced fill-flash" (which includes distance information) and the impact of a flash modifier.

Please use your Nikkor 18-70mm, f3.5-4.5G AF-S IF-ED DX lens* on your D300s with the camera shooting to JPG files, to eliminate software processing variation, and photograph a subject with bare SB600 flash in a darkened ambient light setting at ISO 100, 1/250th shutter speed and f5.6 aperture. (The darkened ambient light environment will insure that most of the scene exposure comes from the flash.) I believe that manual exposure mode is best for this test. You might also try Aperture Priority mode to see if there's any difference.

Now cover the flash head bezel with a single thickness of typing/printer paper over the flash head, but keep all other settings the same.

If the flash does indeed produce a similar exposure in both setups, the bare flash vs the "modified" flash, then you can safely conclude that you are correct that the flash-and-camera does fully compensate for the modified flash output.

If the two images vary significantly in exposure then you can conclude that the "3D Multi-Sensor balanced fill-flash" program places a significant emphasis on the flash to subject distance divided into the guide number and does not properly accommodate the modified flash output.

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*The Nikkor 18-70mm, f3.5-4.5G AF-S IF-ED DX lens is a "G" series lens and should supply distance information to the camera.

wildviper

Nooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo!!!!

My SB600 has died! :cry

Doesn't fire anymore.

I was about to do the test you told me...well...to be continued later...once I get it fixed or get a SB800

basflt

you are all right

it does work , but ,,,,,,,,,,,
it has its limits
outside this limits it does not work [ properly ]

do you shoot in "auto" mode , or manual mode ?????
................. then why set flash to "auto" ?????


me , i mostly do macro
therefor i cannot use auto mode [ the camera software dont "understands" ]
therefor TTL dont work [ the camera software dont "understands" ]

noooooo:nono
i'm in control
not a piece of software from Japan

basflt

i re-read this thread
also did some search

TTL works fine , but
you must adjust it

first
your camera has 2 light-meters
the normal light-meter and the TTL meter
stupid enough , they work seperate from each other

when using TTLflash , you must find the balance
adjust both exposure-compensation and flash-comansation , regardless what your meter in viewfinder says

more exposure-compensation and less flash-comansation = more natural light [ more background ]
more flash-comansation and less exposure-compensation = more supject , [ dark background ]

wildviper

Ok...so I was finally able to do the test as you suggested Ziggy.

Here is what I did.

I used my D300s, with a Tamron 28-75 (I do not have the 18-70 anymore) and borrowed a SB900.

The SB900 was mounted on camera for all the pictures. Settings...ISO 200(sorry Nikon that is the start), 1/250 @f5.6. In a dark room. Only flash exposure was captured and no other light(as proved by the black photo which was without flash). WB was set to Flash.

Image #5200 - No Flash
Image #5201 - Straight Flash on TTL - not TTL BL
Image #5202 - Straight Flash with paper infront - thus the color difference
Image #5203 - Flash head rotate back 180 and bounced of wall behind me - 1foot behind me.
Image #5204 - Flash head straight up - no modifier - bounced to ceiling which is slanting..so not straight ceiling. about 3 feet to 4 feet from flash head
Image #5205 - Bounced into closet on right - it was half open so some light went in there. about 3 to 4 feet away

Here are the images:

#5200 -


Image #5201


Image #5202




Image #5203




Image #5204



- Image #5205




No changes made to anything else. I was sitting and shooting from the same location...yes, my framing may be a bit off here and there...but I tried to be in the same without a tripod. Also, my focus point was the center one...or close that.

Btw, Wall color is creamish

Here is the gallery

To me, this would indicate that TTL for Nikon works the way I have understood it so far....Doesn't matter what you put infront of it...TTL will calculate the light reflected back to camera and thus adjust for it.

And I didn't use a lens that provides distance data to camera...lazy to put on one with that..plus, I wanted to see if Tamron affects camera calcs.

Agree??? More tests??

wildviper

Btw, the histograms for these are exactly the same!

basflt

step outside in daylight and try again , with same settings
i bet they are too dark as it goes with me

as i said , it works fine , but you still have to adjust it

ziggy53

wildviper wrote: »

...

I used my D300s, with a Tamron 28-75 (I do not have the 18-70 anymore) and borrowed a SB900.

...

And I didn't use a lens that provides distance data to camera...lazy to put on one with that..plus, I wanted to see if Tamron affects camera calcs.

Agree??? More tests??

I agree that using a lens without distance information means that you revert to the Nikon TTL flash metering. Nikon TTL flash metering works fine with average scenes but it can get confused by, and be inaccurate in, difficult scenes like:

Scenes with bright or reflective scene elements.
Scenes with black backgrounds or where the background is at some distance behind the subject, especially when the subject does not occupy much of the scene.
Scenes generally much lighter or much darker than average.

Nikon i-TTL, using distance information, does much better in the above conditions and situations, except when there is a flash modifier in place.

Canon E-TTL is similar to Nikon TTL, and Canon E-TTL II is similar to Nikon i-TTL, in the above regards.

wildviper

Ziggy,

what's your thoughts on the diffuser and how it affects Nikon's flash system???? You had mentioned that Nikon flash system doesn't adjust for diffusers. That was your original point and the OP(from previous thread)....does the test above not prove that Nikon system actually does...I see no real difference in the above exposures.

I am not saying about Nikon TTL/i-TTL being correct all the time...more about that it DOES account for diffuser or bounce or whatever with the way it calculates the flash output and keeps it consistent.

ziggy53

wildviper wrote: »

Ziggy,

what's your thoughts on the diffuser and how it affects Nikon's flash system???? You had mentioned that Nikon flash system doesn't adjust for diffusers. That was your original point and the OP(from previous thread)....does the test above not prove that Nikon system actually does...I see no real difference in the above exposures. ...

I agree that your tests with that lens seem to indicate that the Tamron 28-75mm, f2.8 does not relay distance information and that the camera and flash revert to Nikon TTL flash program automation for each image.

wildviper wrote: »

... I am not saying about Nikon TTL/i-TTL being correct all the time...more about that it DOES account for diffuser or bounce or whatever with the way it calculates the flash output and keeps it consistent.

I believe that your results would be somewhat different if you had used a lens which does relay distance information to the camera. This is because Nikon "i-TTL" would probably have been engaged for the flash-forward position with modifier, although not for the bounce positions. I would predict that the flash forward with modifier image should be somewhat under-exposed compared to the other images. I would not expect horrible under-exposure because the distance/guide-number calculation is only a part of the flash exposure program of i-TTL. Most of the exposure will still come from the TTL pre-flash measurements.

wildviper

Isn't i-TTL the same as TTL in Nikons? TTL was for film cameras. I think with Digital, we are in iTTL mode all the time. Unless you have the older cameras D100?? or so that did DTTL. DTTL doesn't even exist anymore in newer systems...D200 and onwards.

If my thinking above is correct, then it shouldn't matter between TTL and i-TTL ...they are one and the same for digital Nikon cameras. And obviously that means that if the head is pointed up, down, sideways...the system adjusts as shown by my test above. No?

I have returned the borrowed SB900 to do further tests...until this weekend.

ziggy53

wildviper wrote: »

Isn't i-TTL the same as TTL in Nikons? TTL was for film cameras. I think with Digital, we are in iTTL mode all the time. Unless you have the older cameras D100?? or so that did DTTL. DTTL doesn't even exist anymore in newer systems...D200 and onwards.

If my thinking above is correct, then it shouldn't matter between TTL and i-TTL ...they are one and the same for digital Nikon cameras. And obviously that means that if the head is pointed up, down, sideways...the system adjusts as shown by my test above. No?

I have returned the borrowed SB900 to do further tests...until this weekend.

Rereading all of the sources and trying to track down the nomenclature I believe that we are both right and both wrong (both partially correct.)

It appears that Nikon i-TTL "is" the current flash automation technology. You are right in that i-TTL is always in use in a current Nikon dSLR.

What changes is "3D Multi-Sensor balanced fill-flash" versus "Multi-Sensor balanced fill-flash". The "3D" system is what I was mistaking in terminology.

Try your test series again when you have the SB900 flash "and" a "D" or "G" series Nikon lens attached. I believe that you will find "some" difference in exposure with flash forward, with and without a modifier, because of the "3D Multi-Sensor balanced fill-flash" metering program not acknowledging the full effect of the flash modifier loss in efficiency.

wildviper

Ok...now that we are on the same page...

yes iTTL BL is totally different than iTTL. Here you may be right about the diffusers and stuff. I do not know about the BL as much...I will re-run the test this weekend and see if TTL BL takes into account diffusers or bouncing.

We shall see what I found out!

Here is a quick link to TTL BL vs. TTL