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taking the red out


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#1 nb9989

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Posted 15 May 2002 - 02:08 AM

I was hoping someone had some advice as to how to bring back the reds lost at depth when the flash was off or turned down to low. In photoshop, using auto levels generally did a good job with that except autolevels does other things that are negatives like sharpening when I don't want sharpening. Does anyone know of an article or something?

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#2 james

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Posted 15 May 2002 - 05:00 AM

This is what "Levels" "Color Balance" and "Curves" are for.

Then again, if the shot doesn't have enough red in it to begin with, you aren't going to have much luck adding more later. Photoshop doesn't generally "know" where to put the red pixels. Have you ever noticed what happens when you auto-level a shot w/ a lot of water in it? The water turns purple, right? :)

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#3 nb9989

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Posted 15 May 2002 - 05:14 AM

Ok then, I noticed that a video guy was using a red filter which I assumed was to bring out or adjust for reds otherwise lost. Is there no way to digitally apply a red filter to get the same end product.

#4 derway

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Posted 15 May 2002 - 08:29 AM

Yes. Ikelite and others sell or provide a "UR-Pro" filter, which is reddish tint, which blocks out lots of blue and green, so whatever red is left, will be relatively stronger, in the light that hits the film/sensor.

There are lots of sample shots with it, on the ikelite web pages.

It is probably too much filter, in the top 20 or so feet of water, (clear water that is), and probably not enough, below 50 or 60 feet.

That is why most people end up bring artificial light down with them. To get consistent results, at varying depths.

I do not believe that levels or auto levels does any sharpening. But it can dramatically increase contrast, which may fool the eyes into thinking it is sharper.

In general, autolevels frequently way over does the adjustment. I found a great photoshop plug in, for adjusting colors, by clicking on various spots in the image, and telling it, "this should be neutral, that should be sky blue, this should be skin", etc.

It is called icorrect professional. Web site here:

http://www.picto.com/productsA.html

Don


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#5 snoack

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Posted 15 May 2002 - 12:02 PM

Instead of autolevels try working with layers and do it manually (no autostuff)
- create a new layer for manual level adjustment and play around with red.
- create a new layer for selective color adjustment and play around with reds and greys. Making red and grey colors a bit less cyan (i.e. adding red) often does the job.
For better control of the outcome select and deselect the layers.

Sabine

BTW: My Photoshop is german, i hope i translated the menus/commands in a way you can recognise them)

#6 Kasey

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Posted 16 May 2002 - 02:47 AM

I'm an UW videographer that is just getting more involed in UW stills. When shooting video, we only use the red filter when not using lights, otherwise - too much red. A still photographer told me that he uses the filters even with the flash. It would be great if the filters are mild enough to help reds in the background, but not overpower the areas in range of the flash. Does the WB of the camera compensate for this in the abscence of a filter?

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#7 Andi Voeltz

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Posted 18 May 2002 - 07:49 AM

Hi Kasey,

I recently talked to an engineer who studied some stuff with light wavelenghts etc. and is also an underwater photographer. He suggested to use the manual white balance of the camera and told me that it should make the use of a filter obsolete. About whitebalancing you can find some user experiences in ** this thread ** I recently started at the forum.

Hope that it helps a little... ;-) .oOo. Andi
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