HDR - AEB Exposure Question

[SilverMercury]

When I practice HDR photography, I prefer using Auto Exposure Bracketing (AEB).

The way I make most of my HDR's is through six exposures, but I delete one image because it's a repetitive exposure around which my question is oriented.

So first let me explain how the AEB works on my camera, because I'm sure not everyone reading uses the 5D Mark II.

1. In AEB, I take 3 images in this sequence: -4 EV, -2 EV and 0 EV.
2. I move my AEB dial to take another three images, this time: 0 EV, +2 EV and +4 EV.

As you can see, 0 EV repeats twice, so I delete one of these exposures because it's not necessary to have both when making the HDR.

My question:

I've noticed that there is a slight change in exposure between the two '0 EV' exposures. This happens every single time I practice HDR, and I have examined the f-stop and shutter speed between the two O EV images, and although the settings are consistent, one '0 EV' image appears slightly different in exposure than the other, and I have no idea why.

Has any else noticed this, or have any explanation why this is? I have always been curious why, and just recently found this HDR forum.

Thanks guys,
Stephen

 

[Overread]

The slight difference might simply be a reflection in the fact that whilst the settings for the two 0 exposures are the same, the light itself has made a small shift resulting in a slightly different exposure. Furthermore it might be that if you are shooting JPEG or have RAW processing software that reads and uses your in-camera JPEG settings as a default, that some special in-camera JPEG processing option is giving one version a slightly different treatment to the other (again a reflection of slight changes).

Disabling auto-editing/optimising features might well negate the problem.

 

[Bynx]

If the lighting is consistent and not changing like a cloudy day where the sun comes and goes, and if the camera settings remain the same, then the output should be the same. If you do see a difference between the two 0EV shots pick the best one and toss the other. Would you mind posting two 0EV shots so we can see what you see?

 

[SilverMercury]

Definitely. I don't have any on my computer at the moment, but I can post some tonight when I get home. I'm very new to this forum, any quick tip on how to post images here?

Another thing I wanted to adress:
The change I notice between the two 0 EV occurs both in-camera and in post-production software (specifically lightroom). In respect to the file extension, I'm shooting .CR2 (SRAW1, I think?) - like 11 megapixels.

 

[480sparky]

.......... I'm very new to this forum, any quick tip on how to post images here? ...........

Click here.

 

[SilverMercury]

Hey guys,

Sorry for not posting last night, the sun had gone down by the time I got home. Anyway, I took a few samples today and - more importantly - I think I figured out the problem. I don't think that I'm witnessing a change in exposure on the 0EV images, I think it's a change in white balance. Traditionally I've left my white balance on the Auto White Balance (AWB) setting, and I think this is what has been causing the apparent change between the two 0EV images.

Anyway, below is a link to three sets of 0 EV images taken in my backyard. The images were taken with a Canon 5D Mark II in SRAW1, file extension '.CR2'. Imported into lightroom 3 and exported as .jpeg images at 1080x720 then uploaded to image shack. The first two sets were taken on the AWB setting, the last set (of the Pepsi can) was taken on the 'Sunny' white balance setting. Whereas in the other two sets I can notice a visible change in white balance, I don't on the third set - but I want your opinions, too.

http://imageshack.us/g/97/hdr0evtestimages1755.jpg/

Personally I'm able to observe the changes in these images more easily when I rotate back and forward between them quickly, so you may need to download them to do that. Anyway, feel free, and thanks in advance for your thoughts.

Best,
Stephen

 

[SilverMercury]

My first ever HDR:


Backyard_HDR_1 by The Higgs Boson, on Flickr

 

[Overread]

Having had a quick look I think you are right, its not the exposure that is changing its the white balance and since you are shooting in RAW mode it should be easy to fix. Just set the camera sit in auto WB for the shots and then, in the editing phase, set the colour and temperature of all the shot to be made into the HDR to the same values (ie setting the same white balance for all). That should eliminate the problem