Exposure Compensation Custom Setting

[TME]

Hi,

Anyone knows what the difference is between the two custom settings for Exposure Compensation... I remember long ago there was a very long discussion with Zerstorer, forbytes, and sulhan about the way the Dynax 7 did its exposure compensation... I never really got it... but last night as I played around with my camera, I decided to try both modes...

The modes are:
1) Ambient only
2) Ambient and Flash

The manual isn't very helpful in that all it states is that for (1), flash exposure is fixed and only the ambient exposure controls (shutter speed, aperture and ISO) adjust the exposure....

And for (2), when using exposure compensation for flash, u can adjust both the flash and ambient exposure controls...

Which of course is Greek to me....

I tried shooting to try to understand what it means and I'm perhaps more lost that before...

All shots, shutter speed 1/60, f/3.5. All comparisons are relative exposures based on the histogram.

Situation 1
Aperture priority
Flash TTL
Custom WB
-1EV; +1EV (flash)

The shot set to Ambient Only (A) is slightly brighter than Ambient & Flash (A&F).

Situation 2
Aperture priority
Flash TTL
Custom WB
0EV; -2.0EV (flash)

No difference in exposure.

Situation 3
Aperture priority
Flash TTL
Custom WB
-2.0EV; 0EV (flash)

(A) exposed properly,; (A&F) was 2 stops under.

Situation 4
Aperture priority
Flash TTL
Custom WB
-2.0EV; +1.0EV (flash)

(A) exposed properly but darker than situation 3. (A&F) was underexposed and looked similar to situation 3 based on histogram again.

Situation 5
Aperture priority
Flash TTL
Custom WB
+2.0EV; -1.0EV (flash)

(A) is underexposed, much more than in situation 3 & 4. (A&F) is properly exposed. Like for (A&F) in situation 1.


So what do the two modes do??? I believe in one mode, the exposure compensation offsets any changes in the opposite direction made to the flash compensation... but which? Will put up pics tomorrow...

 

[UY79]

http://forums.clubsnap.org/showthread.php?t=150883

 

[UY79]

Basically if you understand the link I've posted you can work out the resultant compensation you would get when you use them.

Situation 1
Aperture priority
Flash TTL
Custom WB
-1EV; +1EV (flash)

The shot set to Ambient Only (A) is slightly brighter than Ambient & Flash (A&F).

A: Ambient @ -1EV, Flash @ +1EV
A&F: Ambient @ -1EV, Flash @ 0EV

Situation 2
Aperture priority
Flash TTL
Custom WB
0EV; -2.0EV (flash)

No difference in exposure.

A: Ambient @ 0EV, Flash @ -2EV
A&F: Ambient @ 0EV, Flash @ -2EV

Situation 3
Aperture priority
Flash TTL
Custom WB
-2.0EV; 0EV (flash)

(A) exposed properly,; (A&F) was 2 stops under.

A: Ambient @ -2EV, Flash @ 0EV
A&F: Ambient @ -2EV, Flash @ -2EV

Situation 4
Aperture priority
Flash TTL
Custom WB
-2.0EV; +1.0EV (flash)

(A) exposed properly but darker than situation 3. (A&F) was underexposed and looked similar to situation 3 based on histogram again.

A: Ambient @ -2EV, Flash @ +1EV
A&F: Ambient @ -2EV, Flash @ -1EV

Situation 5
Aperture priority
Flash TTL
Custom WB
+2.0EV; -1.0EV (flash)

(A) is underexposed, much more than in situation 3 & 4. (A&F) is properly exposed. Like for (A&F) in situation 1.

A: Ambient @ +2EV, Flash @ -1EV
A&F: Ambient @ +2EV, Flash @ +1EV

 

[TME]

I'm not sure I got u... but I'm uploading the photos so that maybe u could point out more clearly what is going on... left photo is Ambient only. Right photo is Ambient & Flash.

And what does Ambient & Flash do?

Situation 1
Aperture priority
Flash TTL
Custom WB
-1EV; +1EV (flash)

The shot set to Ambient Only (A) is slightly brighter than Ambient & Flash (A&F).

A: Ambient @ -1EV, Flash @ +1EV
A&F: Ambient @ -1EV, Flash @ 0EV

Situation 2
Aperture priority
Flash TTL
Custom WB
0EV; -2.0EV (flash)

No difference in exposure.

A: Ambient @ 0EV, Flash @ -2EV
A&F: Ambient @ 0EV, Flash @ -2EV

 

[TME]

Situation 3
Aperture priority
Flash TTL
Custom WB
-2.0EV; 0EV (flash)

(A) exposed properly,; (A&F) was 2 stops under.

A: Ambient @ -2EV, Flash @ 0EV
A&F: Ambient @ -2EV, Flash @ -2EV

Situation 4
Aperture priority
Flash TTL
Custom WB
-2.0EV; +1.0EV (flash)

(A) exposed properly but darker than situation 3. (A&F) was underexposed and looked similar to situation 3 based on histogram again.

A: Ambient @ -2EV, Flash @ +1EV
A&F: Ambient @ -2EV, Flash @ -1EV

 

[TME]

Situation 5
Aperture priority
Flash TTL
Custom WB
+2.0EV; -1.0EV (flash)

(A) is underexposed, much more than in situation 3 & 4. (A&F) is properly exposed. Like for (A&F) in situation 1.

A: Ambient @ +2EV, Flash @ -1EV
A&F: Ambient @ +2EV, Flash @ +1EV

 

[Zerstorer]

TME,

Remember the long discussion about 2 years back along with Jerry and Ckiang in the thread where we talked about this? It's basically the same thing.

The reason why the "ambient" only setting seems to have no effect is because you are shooting Aperture priority in an environment where the ambient exposure levels are below the default flash sync speed selected by the camera.*The shutter speed is locked* Hence, ambient exposure cannot be changed at all! All that changes is just the flash exposure.

When in Ambient Only mode, if the shutter speed is locked by the camera, the Ambient EV settings will have no effect.

In the Ambient + Flash mode, when the shutter speed is locked, the camera will divert the ambient EV settings to the flash instead. So in the case of -2EV, +1FEV, it just sums up to be -1FEV.

If you were shooting outdoors in bright daylight where ambient exposure levels are beyond the compensation ranges, they should appear the same. Or if you shoot with the camera in SLOW SYNC mode, they should be identical.

For the detailed explanation WHY, go read the previous post by uy79 on the other thread.

 

[TME]

Basically if you understand the link I've posted you can work out the resultant compensation you would get when you use them.

I've re-read what u posted and I must admit it's pretty confusing and I am confused more so now with my pics in front of me...

1)
(a) So Ambient & Flash are linked... is that what I see in situation 1?
A&F photo is correctly exposed cos +1 FEC and -1 EC cancel out and the net effect is 0EV overall? All EV for later situations are compared against this photo.

(b) And for Ambient only, since the EC ignores what is done for FEC and vice versa, the picture is still overexposed cos the flash is the main source of illumination? But u find that overall Ev is less than +1 ,why?


2) I think I can assume that in the pics posted, the flash is the main souce of lighting... Is this situation 2? Both photos in situation 2 are underexposed after I tuned down the flash.
(a) For Ambient only, EC no effect and the FEC affects the overall EV, so the overall EV is -2.

(b) For Ambient & Flash, FEC is coupled with EC and if flash illumination is cut by -2 then overall EV also -2.

3) In situation 3, I tune down the exposure compensation, but left the flash alone.
(a) Ambient only photo is correctly exposed. Is this what u mean by the camera ignoring the EC with ambient only since the exposure is below the 1/focal length rule? But there seems to be some effect since the picture is a little under compared to situation 1, A&F photo. Why?

(b) Ambient & Flash photo is underexposed cos EC is -2 and since FEC and EC are linked, overall EV is -2. I suppose the effect is to lower the flash to effect -2 EV overall?


4) In situation 4, same as 3 but +1 for FEC.
(a) Ambient only is a tad brighter than situation 3 Ambient only cos this time I have extra help from the flash. Overall EV is -1EV. It's about 1 stop dimmer than situation 1 A&F photo. Why, if EC is not factored in? Should it not be overall +1EV and it should look the same as situation 1 A only photo?

(b) This is easier to understand since FEC and EC linked, overall is -1 so it looks underexposed.


5) In situation 5, opposite settings of situation 4. This one I dun quite understand also... not sure correct or not...
(a) EC is +2 but FEC is -1. Underexposed cos flash is main source of illumination. And +2 EC does not help cos shutter speed will not fall below 1/60s based on Minolta 1/focal length rule. Hence underexposed.

(b) EC and FEC are linked, overall offsetting should yield EV+1. But the shot looks a tad underexposed over situation 1 A&F photo. Might be due to the fact again that the flash is main source of illumination. What I dun understand is why overall it should be +1 EV but again it looks dimmer than A only photo from situation 1?

Additional notes/queries:
1) [Rephrased] In situation where the net effect is +1 EV for Ambient & Flash, the picture still looks a tad under.

2) In situations for Ambient only where the EC is ignored and then FEC is +1, the shot still looks under... given that EC is ignored, then shouldn't the overall EV be +1 from the flash?

3) What UY79/sulhan/Drudkh explained in the linked thread by UY79 does not seem to work all the time.... maybe it's just me.... anyone care to walk me through this mess? :sweat:

Thanks a million! ;p

 

[TME]

TME,

Remember the long discussion about 2 years back along with Jerry and Ckiang in the thread where we talked about this? It's basically the same thing.

The reason why the "ambient" only setting seems to have no effect is because you are shooting Aperture priority in an environment where the ambient exposure levels are below the default flash sync speed selected by the camera.*The shutter speed is locked* Hence, ambient exposure cannot be changed at all! All that changes is just the flash exposure.

When in Ambient Only mode, if the shutter speed is locked by the camera, the Ambient EV settings will have no effect.

In the Ambient + Flash mode, when the shutter speed is locked, the camera will divert the ambient EV settings to the flash instead. So in the case of -2EV, +1FEV, it just sums up to be -1FEV.

If you were shooting outdoors in bright daylight where ambient exposure levels are beyond the compensation ranges, they should appear the same. Or if you shoot with the camera in SLOW SYNC mode, they should be identical.

For the detailed explanation WHY, go read the previous post by uy79 on the other thread.

Hi Zerstorer, I remember that very long discussion but I really didn't get it then either I think... at least I think so now...

What u mention briefly makes complete sense but I can't seem to apply it to the photos I took.

In situation 5, for Ambient only. Since EC is not used, then overall -1 due to FEC -1 is correct from the photo. But for Ambient & Flash, if the EC is diverted to FEC, then overall should be +1EV. But u notice that the shot looks under by about 1 stop or less... compared to situation 1 Ambient & Flash (where EC-1 FEC +1)

 

[Zerstorer]

2) What UY79/sulhan/Drudkh explained in the linked thread by UY79 does not seem to work all the time.... maybe it's just me.... anyone care to walk me through this mess? :sweat:

Note that only UY79's explaination is correct in that thread. That's why I specifically mentioned his post.

This is not so difficult to figure out if you understand how ambient exposure is varied in the first place when certain parameters are fixed.

It's like equations, when u vary one parameter and fix another, something else has to change to balance up the equation.

 

[TME]

Note that only UY79's explaination is correct in that thread. That's why I specifically mentioned his post.

This is not so difficult to figure out if you understand how ambient exposure is varied in the first place when certain parameters are fixed.

It's like equations, when u vary one parameter and fix another, something else has to change to balance up the equation.

I'll think about it again... in the process of reworking my questions in the previous post.... thanks!

 

[Zerstorer]

Hi Zerstorer, I remember that very long discussion but I really didn't get it then either I think... at least I think so now...

What u mention briefly makes complete sense but I can't seem to apply it to the photos I took.

In situation 5, for Ambient only. Since EC is not used, then overall -1 due to FEC -1 is correct from the photo. But for Ambient & Flash, if the EC is diverted to FEC, then overall should be +1EV. But u notice that the shot looks under by about 1 stop or less... compared to situation 1 Ambient & Flash (where EC-1 FEC +1)

The thing is you didn't state fully the shooting conditions of your test. What was the ambient exposure like? If at any point in time the ambient exposure is higher than the flash sync speed, it would allow the EV compensation to take place and affect the result.

Moreover, when shooting at such a wide angle with Matrix/honeycomb metering, there may be slight variations in exposure based on the camera's algorithm. One or 2 shots that seem out isn't really significant in this case. If you want to really test, shoot an even coloured test target under spot/centre weighted metering to ensure that there will be no variation.

Basically, you are holding a DSLR, do more shooting tests to ascertain its idiosyncrysies and characteristics to have a good feel of how it reacts in various situations.

 

[TME]

Ambient was f/3.5, 1/10s at 17mm on ISO400. So it was way below the 1/60s rule. I dun think the EC would kick in if what the manual mentioned regarding the Ambient only mode is correct. I had the camera mounted on a tripod and took the shots using the 10s timer.

The thing is that the +1 FEC shots are consistently a tad under what I would expect based on the explanation u and UY79 gave... wonder if the EC completely disabled under sub-1/60s conditions?

Edit: changed the ambient conditions, just went to meter it again using the same settings of matrix metering.

 

[TME]

Basically, you are holding a DSLR, do more shooting tests to ascertain its idiosyncrysies and characteristics to have a good feel of how it reacts in various situations.

Will try some more settings... although idiosyncratic, the camera should behave predictably? I mean it does, i.e. underexpose consistently in each of the situation 2 to 5 as I pointed out... but I'm looking for some explanation... Anyway I chose 17mm cos that is the focal length I use most indoors for group shots. I wanted to sort out the nuances of EC and FEC... but it seems to have given me more questions that answers... :sweat:

Thanks a zillion btw...

 

[UY79]

I don't know where to begin answering. So let me just say something in this post.

Your shots look like what would be expected except that some are a tad under and over. Bascially, all flashed shots with the same resultant flash exposures should look the same but they are not.

Keep in mind that there's always ambient exposure and flash exposure. The custom setting is just to link the compensation for the 2 exposures together or keep them seperate. There's no such thing as overall compensation. They are always seperate. The dominant exposure after compensation will make up the exposure for your shot.

 

[muko]

I don't know where to begin answering. So let me just say something in this post.

Your shots look like what would be expected except that some are a tad under and over. Bascially, all flashed shots with the same resultant flash exposures should look the same but they are not.

Keep in mind that there's always ambient exposure and flash exposure. The custom setting is just to link the compensation for the 2 exposures together or keep them seperate. There's no such thing as overall compensation. They are always seperate. The dominant exposure after compensation will make up the exposure for your shot.

humm??
Yes this discussion very technical and confusing...
technically confusing...

seems like i understand your last comment bro...
Same as my thinking.
But i prefer to separate them both.
Because i use flash mostly to take nighttime self picture.
So i need the background from ambient exposure and i need myself from the flash (i mean so that i can appear sharp also).
Like this ka?

if yes... then when should i use to "not separate" ambient and flash?
any idea of applications?

 

[funhur]

Ref UY's post in the other thread, http://forums.clubsnap.org/showpost.php?p=1533527&postcount=6

when using Ambient&Flash mode, does it means that the EC will "add on" the FEC but not vice versa. hmm, anyway the "addition" cannot be cyclical right ?

it seems that using Ambient mode is more "direct" in the sense that each compensation is as exactly set

 

[UY79]

Yes, you can choose to control ambient EC and FEC individually using Ambient Only setting. This setting allows the EC to follow as what the knobs indicate.

In Ambient+Flash setting, resultant FEC is an offset based on the set FEC(on the knob) on the ambient EC(which means to calculate the resultant FEC, you have to add them up)

Like I mentioned. The ECs are seperate. Here are more examples of how the resultant compensations are derived.

1) Lets say you are using Ambient only setting. You adjust your EC to -2EV leaving FEC at 0EV.

Ambient EC = -2EV, Flash EC = 0EV.

Adjusting FEC knob later will be make the resultant flash exposure to what the FEC knob is set.

2) If you are using Ambient + Flash setting. The same setting gives you the following. This is because the 2 ECs are linked.

Ambient EC = -2EV, Flash EC = -2EV.

In this case, resultant flash EC will be an offset of the set ambient EC (-2EV). If FEC is set to 0EV, flash EC is -2EV. And if FEC is set at +2EV, flash EC is 0EV.

Ambient+Flash setting allows you to control just one knob to lower the overall exposure when your shots overexposes. To do it in Ambient Only, you would have to adjust both knobs.

 

[TME]

I think I understand now...

When using Ambient & Flash, the EC does not change but the final FEC output is calculated by adding the EC + FEC set on the camera.

With Ambient Only, the EC & FEC set on the camera do not affect one another. They affect the exposure separately but their effect is of course cumulative.


Thanks!!! Maybe I will do another set of photos to explain to those who are still confused...
Thanks UY79 and Zerstorer for both your patience...

Edit: I think it is easier to use Ambient Only... less to think and compute...

 

[kueko]

I have always wanted to test this out. Thanks for posting the test shots, those photos speaks many thousands words. Using words to explain is quite confusing as too many similar terms are used. If you are doing some more test shots, can I suggest you try out what UY79 suggested in the other thread.

In Ambient Setting : EC = -2EV, Flash EC = +2EV
In Ambient & Flash Setting : EC = -2EV, Flash EC = 0EV

Theoretically, both photos should look the same.

Bottom line is if you want to adjust ONE EV, use the Ambient & Flash Setting. If you prefer to adjust BOTH EV, use Ambient Setting.

To make the test more "foolproof", set it to Shutter Priority (1/60 or whatever that is lower than the flash sync speed) and include the meter readings in the test result. To make it more "complete", take a shot without any compensation (EC = 0EV, Flash EC = 0EV) to see if all these compensation makes any difference.

Still using D7 SLR, will be broke if I run all these test!