fixing underexposed photos

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BillZM
Posts: 17
Joined: 16.07.2006 01:38

fixing underexposed photos

Unread postby BillZM » 23.09.2007 17:33

We have a bunch of wedding pictures with some critical ones significantly underexposed (flash problems perhaps) by perhaps 2 stops or so.
What Helicon workflow have others found to try to fix seriously underexposed images? I can simply increase Gamma (v4.71 offers a setting called "Brighter" which sets Gamma to +31). But should I be adjusting contrast, saturation, and white balance too? I'm hoping to find the right fix for about 100 images; I don't want to have to agonize over each individual photo. Hoping to learn from others' experience...

lutz
Posts: 155
Joined: 14.04.2006 02:51

Unread postby lutz » 24.09.2007 07:49

Bill,

could you post an example? It does not have to be full sized. This would certainly help.

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Dan Kozub
Posts: 1157
Joined: 24.03.2004 18:14

Unread postby Dan Kozub » 25.09.2007 16:27

I am using Autocontrast (conservative, 25%) + Local contrast in such cases.

BillZM
Posts: 17
Joined: 16.07.2006 01:38

pictures

Unread postby BillZM » 26.09.2007 12:13

Here are some pics (all processed in Helicon filter 4.71 with moderate sharpening, then resized to 800x600). Otherwise...

as taken
http://i14.photobucket.com/albums/a319/ ... _hf_FS.jpg

Gamma+7 LocalContrast=1 WhitePoint=0 AutoContrast=25
http://i14.photobucket.com/albums/a319/ ... C25_FS.jpg

Gamma+35
http://i14.photobucket.com/albums/a319/ ... G35_FS.jpg

Gamma+35 Saturation-12
http://i14.photobucket.com/albums/a319/ ... -12_FS.jpg

Gamma+35 Saturation-18
http://i14.photobucket.com/albums/a319/ ... -18_FS.jpg

I wonder if the linear color space (no Gamma transformation) new to v4.71 is helping here.

Basically it appears to me that Gamma is mostly all I need to worry about, except that the underexposed pics are overly saturated. As a general rule with this set of pics as shot (camera settings), it appears that a saturation correction of -1/2x to -1/3x that of the Gamma correction seems to give a good result. Any thoughts / comments?

lutz
Posts: 155
Joined: 14.04.2006 02:51

Unread postby lutz » 27.09.2007 05:29

Hi Bill,

your ideas work indeed very well. It is amazing how little noise is coming up despite the photo being so severely underexposed.

Here is my variation: contrast +9, gamma +20, exposure +2.0, saturation -42 and -12.


http://img136.imageshack.us/img136/412/partyxt4.jpg

with some retouching

http://img206.imageshack.us/img206/1203/party2pc5.jpg

BillZM
Posts: 17
Joined: 16.07.2006 01:38

Unread postby BillZM » 27.09.2007 12:37

Lutz, thanks for taking a look. I posted a comment on another thread too referencing this. I think it would be great if there were a button or checkbox for "autoexposure" (either Gamma or exposure correction in this context) to get average value on image to a certain number. That would be a great starting point for these corrections. Especially nice if there were an adjustable factor attached for saturation correction too. With a bit of automation, batch processing would seem possible.

I wasn't sure the contrast adjustments were helping.

This particular image was shot on a Nikon D200 producing a 6MP image (vs native 10MP); an odd choice (to save space, I guess) but that's what the photographer did. ISO400. Yes, it seems to exhibit very little noise, even at larger sizes. Very usable. I didn't use Helicon's noise tab at all (at least yet) though I did sharpen it a bit (which presumably would have made any noise more visible).


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