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Standarize for variation in light between photos

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Maria Tesaker
Standarize for variation in light between photos
on Jan 15, 2013 at 4:08:04 pm

Hi!

I am a biologistudent, and I am studiyng bird plumage. Therefor I have many photos with a lot of variation in lighting, and I am looking for help to find a good way of standarizing my photos for colour value measurements (mean and SD from the histograms in Photoshop).

This is my problem:
Variation in the birds in the photos (e.g in the crown, different colours)
variation between photos, independently from variation among the birds
variation within the photos (the amount of light varies in different areas of the same photo)

How do I standarize for variation between photos for the influence of ambient ligth of the specific area of the photo I want to measure? (e.g crown of the bird)

I need to be able to withdraw the comparable colour measurements from different photos (and its too late for a better method for actually take the photos.)

hann.hus.side.cees.conf.png

hann.hus.bib.cees.conf.png

I have tried to use the white background (going down to pixel level, avoiding the orange grid and dirt) and the yellow post-it note as points to standarize, but that didnt work.
Technical info:
- I use Adobe Photoshop CS6, updated this week
- On a Windows 7 Home Premium computer
- Uploading the images as NEF-files and saving them as psd-files
- RAM: 4,00 GB (3,84 GB uasable)

Hope someone can help or give me a clue what to continue to work on.
Thanks!


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Jonathan Ziegler
Re: Standarize for variation in light between photos
on Jan 16, 2013 at 7:15:54 pm

Egads. I see your dilemma. I have 2 suggestions:

1) since the photos thus far have been shot on a variety of backgrounds and none of them are plain white for the camera (they look white, but there are subtle color variations that adjust the colors slightly so correction is difficult) or calibrated for white balance or exposure, I would use the auto correct feature in Photoshop Raw for each image. You may get some weird results and you will have to play with your pix. This may take some time. You can use levels to balance the histogram, but I'm not sure how to make this an action. You may wind up sacrificing some quality, contrast, or other factors to get the right exposure.

2) shoot the rest of your pictures by first calibrating your white balance, use some type of standard manual setup - write it down so you don't forget, then use the same lighting - may want to get a ring flash for these types of photos. Using the same flash every time qualifies as standardized lighting and will make calibration easier. Get a small white/grey balance card. I have a small lastolite one I got on Amazon that rolls up like a car visor for really cheap or you can use another sort of "standardized" white balance card.

If anyone else wants to chime in who has done this, it would be good. :)

Save early. Save often.

Jonathan Ziegler

http://www.electrictiger.com
520-360-8293


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