Better understanding Photoshop's Auto commands and adjustments

Started Jul 28, 2009 | Discussions thread
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sethmarshall Regular Member • Posts: 153
Better understanding Photoshop's Auto commands and adjustments

Last week I started a thread titled "What is your "quick" everyday workflow (i.e. auto adjustments)...." here: http://forums.dpreview.com/forums/read.asp?forum=1014&message=32462972

There was some great feedback given and I thank everyone who replied. I don't mean to repost but I wanted to better title my question to more specifically address my concern.

I think we can all agree most people stay away from any sort of AUTO adjustment and do it by hand. Further it was agreed it's best to work with adjustment layers. But there was difficulty answering the specific questions on what each perimeter does that is specifically different from other perimeters. Maybe people assume the name of that tool is the answer. Others seemed to ignore this concern perhaps because they've really never thought about it themselves. I want to hear your opinions on each adjustment perimeter and how it fits in your workflow.

Here I am speaking of two specific areas in Photoshop:
1. IMAGE > AUTO TONE or AUTO CONTRAST or AUTO COLOR
2(a). IMAGE > ADJUSTMENTS > (all these perimeters in the drop-down menu)

2(b). LAYER > NEW ADJUSTMENT LAYER > (all these perimeters in the drop-down menu)

I know that's three (not two) areas, but the adjustments in 2a and 2b are the same perimeters. The difference being how they're applied, in layers or not. In the manual it warns when not working with layers "...keep in mind that this method makes direct adjustments to the image layer and discards image information." Please let's assume we're talking about working with layers because I don't want this to get off track. I am also interested in learning why there are additional perimeters in the 2a area that's not in 2b (the six at the bottom) and what those perimeters do that can't be done in other adjustment perimeters... But first:

My issue is that it seems some adjustments are redundant in that their effects can be seen using different perimeters also. This was debated in my original thread. After re-reading the manual I have evidence that I was right, partially. (See my excerpts at the bottom)

It appears to me by the manual that Auto Tone does something similar to the auto option in levels and curves. It then explains since it adjusts each color channel individually, it may remove color or introduce color casts.

Auto contrast, on the other hand, does not adjust channels individually and does not effect color at all as a result. And Auto Color also does not adjust channels individually but searches to identify shadows, midtones, and highlights and using the method of neutralizing midtone target RGB 128 gray adjusts the contrast and color.

I'm only citing these 3 perimeters which aren't even under the adjustments or adjustment layers pull-down menu. My point is WHICH perimeters do you use for certain situations since it appears they are all tied in together?

It seems everything is complicated as could be expected but I was correct to some degree there is a redundancy in these perimeters that other perimeters control as well. I know everyone says "don't use AUTO" anything but I use this as example that the adjustment features are confusing not just to me but to those experienced users who claimed that certain features didn't overlap in their abilities.

Sorry this is so long. I simply find it frustrating and hard at times to state my question in a way that people understand.

AUTO TONE from the manual:

The Auto option for Levels and Curves and the Auto Tone command automatically adjust the black point and white point in an image. This clips a portion of the shadows and highlights in each channel and maps the lightest and darkest pixels in each color channel to pure white and pure black. The intermediate pixel values are redistributed proportionately. As a result, using the Auto option or Auto Tone increases the contrast in an image because the pixel values are expanded. Because the Auto option and Auto Tone adjust each color channel individually, it may remove color or introduce color casts.

AUTO CONTRAST from the manual:

The Auto Contrast command adjusts image contrast automatically. Because Auto Contrast does not adjust channels individually, it does not introduce or remove color casts. It clips the shadow and highlight values in an image and then maps the remaining lightest and darkest pixels in the image to pure white and pure black . This makes the highlights appear lighter and shadows appear darker.

AUTO COLOR from the manual:

Auto Color adjusts the contrast and color of an image by searching the image to identify shadows, midtones, and highlights. By default, Auto Color neutralizes the midtones using a target color of RGB 128 gray and clips the shadowand highlight pixels by 0.5%. You can change these defaults in the Auto Color Correction Options dialog box.

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