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09/07/2005 10:31:48 AM · #1 |
Lately I have really been trying to improve many of my deficient skills. One of them is post processing. Hence I have been reading a lot more of the tutorials, mentorship threads, posts describing various tools and how to use them on this site as well as others.
One area that seems to be unclear or confusing to me is when to use levels and curves. Just referring to the two threads posted here (one each on levels and curves) that can be found linked to in the Color mentorship thread, I am confused.
The post on Curves says you should use Levels FIRST. So in trying by example I opened a few pics and experimented. And this is where the confusion comes in. If you use levels first and adjust as the thread says, when you go to use curves (tone map in PI), the histogram is rather flat and the effects are minimal without extreme adjustments which just don't look right.
If you use curves first and then go to levels, again the histogram is flatter than it was, but you do not need to go to such extremes to get useful adjustments and it seems you have more room to work.
So which do you use first and can someone explain exactly why it is beneficial/important to use them in that order? |
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09/07/2005 11:32:03 AM · #2 |
I would also be interested to hear of any recommended processing order, including order for application of adjustment layers (the order of the layers will dramatically affect an image) - which I tend to approach in a mix & match ad hoc manner.
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09/07/2005 11:43:26 AM · #3 |
| Not sure there is a definitive answer on this. I usually start with levels and work my way down. However when processing my images it is not uncommon for me to go back and re-vist curves 3-5 times during the processing of the image to make little tweaks here and there. |
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09/07/2005 11:55:35 AM · #4 |
Here's a little experiment for you: open an image that's way out of whack levels-wise and use auto levels on it; see the color shift? Or open any image and shift the levels a LOT manually, and watch the colors change.
In general, it makes more sense to adjust levels/curves first, then work on colors, for this reason.
As to order of levels/curves, I generally use levels to set my light and dark range, then use curves to adjust the rendition of the middle tones if needed. Often curves are not needed.
I generally use selective color before hue/saturation if I'm going to use both. If the overall tint of the image needs adjusting, selective color works best for me usually. I use hue/saturation to adjust the relationship between colors.
Both hue/saturation and selective color can be used to some extent to adjust the overall light/dark aspect of the image, and its contrast, as well. ue/sat can effectively introduce contrast to a flattish image if you darken some color ranges and brighten others. For example, if your lighting is fairly flat and you have a lot of grass in the image, you can saturate-and-darken the green channel and saturate-and-lighten the yellow channel and get more textured-looking and luminous grass. With selective color you can darken the black range and lighten the bright range to a certain extent while adding (or subtracting) color as needed, and produce a tad more of a sense of luminance that way as well.
However, they are all interdependent. This is why adjustment layers are so important; each time you change one parameter, the others may need tweaking.
Robt.
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09/07/2005 11:58:44 AM · #5 |
i adjust/correct photos for a magazine publishing company, so this is mostly RGB adjustments for a custom CMYK profile for offset or web printing.
this is mass processing, so this all goes pretty fast. Most simple images would be around 15-30 seconds.
first thing i do is crop and use the perspective correction aspects of the crop tool to correct for lens distortion, if needed.
1. Shadows/Highlights [if needed] for subtle adjustments of dark areas. Careful not to make it glowing-round-the-edges crap.
2. Fix things using the healing tool and the clone tool on a new layer, adjust opacity of that layer for some things--like wrinkles, etc...to bring them back slightly. Helps it not look plastic.
3. Curves adjustment layer, to brighten up a bit, set the gray point.
4. CMYK gamut warning view to see which colors are completely f*cked.
5. If it doesn't look to bad, i convert to CMYK, hit my size/resolution/save as macros. The Macros save a lot of time. If you are looking to speed up your process, that is a great way.
6. If it is really bad and the color is important--bigger images needed or its a beautiful red flower in a sea of green--i'll continue to use hue/saturation, levels, and curves adjustment layers--with the CMYK gamut warning on--and try to make the colors survivable. A final selective color layer to bring back blues and adjust greens.
7. Stretch, get more coffee.
8. I also use the layer mask functions for the adjustment layers, so i'll have one for the sky and one for a building and one for the foreground, depending on what is needed.
I tend to never use auto--even though i've adjusted it so that my black and white clipping points are at .01% or so, and do a fairly good job.
Brightness/Contrast is avoided at all costs...i always recommended to students that they learn to use Levels for brightness/contrast adjustments, so that you can see the histogram and you have more control. You can also turn on the histogram as a palette window, and watch the effect Curves adjustments have. It is basically doing the exact same thing...just with a different interface.
I also tend to use series of layers...even several curves layers for instance, rather than trying to get it all perfect with one. I like warmer shots...some correct a bit more towards cool...a lot of it is very subjective unelss you have specific guidlines.
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09/07/2005 12:28:41 PM · #6 |
Originally posted by Alienyst:
So which do you use first and can someone explain exactly why it is beneficial/important to use them in that order? |
I was getting confused about this a couple of weeks ago as well. So now I'm doing levels first, and then curves (as adjustment layers)
Levels makes it easy because you're working with a visual representation of the histogram. And all I really do with levels is stretch the histogram (i.e. move the left and right sliders in) to set light/dark points - I don't touch the middle slider, I think that's best left for curves.
I see levels as just the quick way to set the light/dark points (stretch the histogram, and get rid of that dead area to the right or left)
For the main curves adjustment layer, I then put the three line anchors in place as a minimum to allow an 's' curve.
But I can see no reason why you can't do the same thing using curves layers alone (keeping an eye on the histogram in the info window when you're making the light/dark point adjustment)
I've noticed no difference between using 1 levels + 1 curves layers versus 2 curves layers, using the bottom one for light/dark points. |
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