image brightness variation

Shooting in macro mode, techniques, tips & tricks

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hondoguy2

image brightness variation

Unread postby hondoguy2 » 01.12.2011 14:53

If I shoot a stack of images in outdoor light and the light intensity changes during the exposure sequence, I get a message when processing the stack in HF that brightness varies 22% or something to that effect.

Is there a way to equalize the exposures in HF or in Lightroom to solve this problem before running the stack? I have tried doing it manually in Lightroom with mixed results. I have a stack now that I can't work with because I can't equalize the brightness.

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Stas Yatsenko
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Re: image brightness variation

Unread postby Stas Yatsenko » 04.12.2011 12:27

Helicon Focus is trying to equalize the stack and in most cases does it very well. But the program warns you about about potential problem.

If the brightness of all parts of the image is changing uniformly, Helicon Focus will have no problem in adjusting the brightness. In case if object is lighted differently and background has constant brightness, the program will not be able to correct this effect properly.

wsingles

Re: image brightness variation

Unread postby wsingles » 25.12.2012 20:08

I have seen this problem more often recently. I am taking pictures indoors in a closed room. I use two professional quality off camera flash units for lighting. Camera is a D800E Nikon. I have not been able to figure out where the lighting variation is coming from. Is the software trying to say that the flash uni is varying output 15 to 20% on each shot?

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Stas Yatsenko
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Re: image brightness variation

Unread postby Stas Yatsenko » 27.12.2012 15:56

We can check if this is true. You can take RGB value of the same spot on all of the source images and see if the different is that big. Please also get measurement of the background too, its brightness can vary if the camera is moved toward the object.

If you send us downsized images, we can check this for you. Please upload samples as described at http://www.heliconsoft.com/ftp.html

thenickdude
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Re: image brightness variation

Unread postby thenickdude » 14.06.2013 10:17

I realize this is an old topic, but I've figured out how to solve this in Lightroom.

I had a series of images illuminated by daylight where not only did the brightness change (as the sun went near edges of clouds) but also the colour temperature.

I selected the whole series in Lightroom, then clicked the "auto tone" button. This chooses exposure settings automatically, and since the images are so similar, it tends to equalise the brightness between the images. I found that it set kind of random values for black-point, white-point, shadows, highlight and contrast, so I set those up correctly on one image and then used the Sync Settings option to copy those settings to all of the photos, leaving only the Exposure varying between shots.

Then I selected Auto for white-balance, which again made the images very similar to each other. It wasn't the correct white-balance, but it doesn't seem possible to (for example) add 500K to every photo in the selection (it just ends up changing the white balance of every photo to be the same). So I ignored the wonky white balance and sent the results off to Helicon Focus.

This time, Helicon merged the images perfectly with no weird brightness transitions in the image, and no warning about image brightness differences.

Finally, I corrected the white-balance of the resulting image in Lightroom.

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Stas Yatsenko
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Re: image brightness variation

Unread postby Stas Yatsenko » 17.06.2013 10:58

Thanks for the hint! Have you tried method C? It should be less sensitive to brightness and wb changes.


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