Levels and Curves

[inkista]

Just one more supplemental link: the Chromasia Levels/Curves tutorial. It's a whopping 5 pages long, but it helped unlock "aha!" moments in my head about these tools.

[Brownbear]

Thank you so much Kathy.. I will review this week.. I really need to unlock several "aha!" moments in my head about levels and curves, so truly appreciated.

Just one more supplemental link: the Chromasia Levels/Curves tutorial. It's a whopping 5 pages long, but it helped unlock "aha!" moments in my head about these tools.

[inkista]

You're welcome. The mousovers which show you the levels or curves for a given image are particularly useful.

For me, the easy way to think about Levels is that it's editing your histogram. The easy way to think about Curves was being able to do Levels corrections at any point in the dynamic range.

[Mike Buckley]

[Regarding] setting the tone curve in your camera... I can in fact do this with my Nikon D80

You're close with that comment but not quite right...or maybe it was my explanation that wasn't adequately clear. I was trying to explain that later model cameras than yours allows the photographer to upload a custom curve created by the photographer. I'm reasonably certain that the custom curve can be created only using Nikon Capture NX2 post-processing software. [EDIT: Instead, it might be Nikon Camera Control Pro as noted in a post shown below.]

It has been a long time since I have used my Nikon D80 (it's a backup camera), but I don't think it has that capability. [EDIT: It does have that capability also noted in a post shown below.] It does have certain presets that were designed by Nikon's engineers. However, those presets include more than the curve; they also include parameters that affect saturation and perhaps other details that escape me at the moment.

To finally (at last!) get to your question about whether we photographers tend to use custom curves or the various presets built into their cameras, I don't. I shoot all of my images in RAW using the "Standard" preset built into the camera. Part of the reason is that I use Nikon Capture NX2 to post-process all of my images. That software includes all of the presets built into the camera, so I can easily make that change during my post-processing.

As I write this, I suddenly realized that I don't even know whether my primary camera allows me to upload a custom curve that I have designed. That speaks volumes about the importance to me of capturing images using custom curves.

However, custom curves designed by the photographer do have their place. As an example, I know of a photographer who, if I remember correctly, shoots RAW files while photographing equestrian events. He sells images to the riders, their friends and family. Rapid turnaround is important in that situation. The lighting and other challenges are apparently reasonably the same at the events that he photographs. He has decided upon a custom curve used when photographing the riders and their horses that reduces post-processing time to a minimum. That of course makes it possible for him to rapidly present images for sale to his prospective customers.

Make sense?

[Brownbear]

Hi Mike,

You're right, my Nikon only allows me to choose preset curves and I did not realize that these curves also affected other parameters such as saturation. Anyway one day I will upgrade my camera and it is good for me to know about custom curves for future.

Makes perfect sense and also good to know. As always thank you for your help and advice.

Christina

[Mike Buckley]

You're right, my Nikon only allows me to choose preset curves and I did not realize that these curves also affected other parameters such as saturation.

Considering that you're on a quest to fully understand curves, it's important to understand that no curve affects the saturation or at least should not affect even the perception of saturation when used accurately. The Picture Control presets built into the camera that you and I are discussing include the curve, the saturation parameter and other details. Once your use of photography vocabulary becomes accurate, which understandably takes time, people like me will no longer be able to confuse you.

Speaking of that, I have to correct something that I wrote earlier that has completely misled you. I believe your Nikon D80 does in fact allow you to construct a custom tone curve and upload it to the camera. Check out the discussion of tone compensation on page 80 of the manual. The software that it mentions is described here. My earlier post about that is now corrected.

[Brownbear]

Thank you, Mike... Yes, indeed and I'm very much looking forward to that day

Jeez, another thing to learn sooner rather than later.. Truly appreciated. Thank you for the link.

[John Morton]

Hi, Christina;

I have a fairly basic approach to Levels and Curves, both of which I often use.

I employ Levels to 'shape' my photo's output to the dynamic range available; that is to say, I use Levels to bump the black threshold up to maybe 4 or 6 (to make sure I have actual blacks in the image) and to pull the highlights threshold back a little closer to where the last white-ish tone is on the histogram, should that be overly far from the top of the scale. In other words, if my top tome is 210 then I will drag the top white threshold down from 256, toward 220 or something like that.

then I use the middle slider, the gamma, to adjust overall image brightness. I tend to do this with every image, more or less. This allows me to more accurately align the tonal range of an image with the 'space' in which it is displayed - which is to say, really, that I use Levels to define the overall image contrast.

If there are specific areas or tones or colors in an image that I need to make distinct from what is around them, then I use Curves to selectively adjust those areas. Making the part of the curve that passes through such an area steeper increases local contrast in that are; flattening the curve out a bit lowers the contrast. I will often put in anchor points above and below the areas I am going to shift, which results in that characteristic "S" curve being produced when the section between the anchors is then adjusted.

There are a lot of other things that can be done with Levels and Curves, but that is how I tend to use them most often.

[jcuknz]

While the discussion above seems to me to be on tweaking an already good photo it can be fun to use curves to achieve a psuedo solarisation effect so instead of a line or 'S' curve you organise a W or M curve or whatever you fancy looks interesting.
Maggie Emerging with insert of approximately what the curves line looked like.


Curves as an adjustment layer is normally the first tool I go to in Post Processing. The advantage of ALs is that you have not changed the original and can with different layers try variations and toggle them on and off to compare.

"not changed the original" is really a false arguement as in a properly organised system you always have a copy of the camera file stashed away somewhere and you are working on a duplicate, not a copy, of the camera file. In my case the duplicate files are on separate hard drives. My 'working' drive and my 'storage' drive which holds both original camera files as out of camera and also worked up files of no immediate need. Storage is relatively cheap these days to the importance to each of us of what we are doing.

[Brownbear]

Thank you John, for a very practical and applicable reply. I have not seen your photos in a while and miss viewing them.

I'm not quite sure I'm grasping your first paragraph... Could you possibly simplify this? Also, not every photo has black in it, or do they because they all have shade of grey to bring out? And you would only pull the highlights threshold back if they were blown?

Hi, Christina;

I have a fairly basic approach to Levels and Curves, both of which I often use.

I employ Levels to 'shape' my photo's output to the dynamic range available; that is to say, I use Levels to bump the black threshold up to maybe 4 or 6 (to make sure I have actual blacks in the image) and to pull the highlights threshold back a little closer to where the last white-ish tone is on the histogram, should that be overly far from the top of the scale. In other words, if my top tome is 210 then I will drag the top white threshold down from 256, toward 220 or something like that.

then I use the middle slider, the gamma, to adjust overall image brightness. I tend to do this with every image, more or less. This allows me to more accurately align the tonal range of an image with the 'space' in which it is displayed - which is to say, really, that I use Levels to define the overall image contrast.

If there are specific areas or tones or colors in an image that I need to make distinct from what is around them, then I use Curves to selectively adjust those areas. Making the part of the curve that passes through such an area steeper increases local contrast in that are; flattening the curve out a bit lowers the contrast. I will often put in anchor points above and below the areas I am going to shift, which results in that characteristic "S" curve being produced when the section between the anchors is then adjusted.

There are a lot of other things that can be done with Levels and Curves, but that is how I tend to use them most often.

[Brownbear]

Hi Photo Nut,
Thank you for your reply. I'm truly sorry but I don't understand what you are trying to share with me. Is the idea for me to play with your photo and try out strange curves to learn the effects of the different and odd shapes?

Thank you.

While the discussion above seems to me to be on tweaking an already good photo it can be fun to use curves to achieve a psuedo solarisation effect so instead of a line or 'S' curve you organise a W or M curve or whatever you fancy looks interesting.
Maggie Emerging with insert of approximately what the curves line looked like.


Curves as an adjustment layer is normally the first tool I go to in Post Processing. The advantage of ALs is that you have not changed the original and can with different layers try variations and toggle them on and off to compare.

"not changed the original" is really a false arguement as in a properly organised system you always have a copy of the camera file stashed away somewhere and you are working on a duplicate, not a copy, of the camera file. In my case the duplicate files are on separate hard drives. My 'working' drive and my 'storage' drive which holds both original camera files as out of camera and also worked up files of no immediate need. Storage is relatively cheap these days to the importance to each of us of what we are doing.

[John Morton]

Hi, Christina;

No, I have not been posting in a while because I have been 'otherwise occupied' with my fiance, Julia Lee Barclay, who is presently visiting me here in Canada from her home in Manhattan.

Levels for me, on an adjustment layer, are primarily of use in defining the contrast range of a photo; that is to say, in getting the range of tones in the photo to match that available for display. So, if 256 levels of grey are available then Levels can be used to more accurately distribute the levels in the image over that range of 256 levels. It is a rare photo that does not have something which does or can or should look black, regardless of whether the camera sensor renders it as a lighter grey or not.

The nice thing about using an adjustment layer for Levels is that one can then fade that layer to 80% so that nothing is actually rendered as a solid blocked-in black which hadn't been that way to begin with.

I often have histograms that have a lot of empty space on the white end, because I shoot a lot of images in darker conditions. So in pulling the white level down, I am just trying to stretch the levels I have captured out over the available space in which they can be displayed. This will however blow out highlights if they are there and tight up against the white end of the histogram.

[Mike Buckley]

Levels for me, on an adjustment layer, are primarily of use in defining the contrast range of a photo; that is to say, in getting the range of tones in the photo to match that available for display.

Based on the helpful explanation that you provided in your first post, I think it's more accurate to say that you are using Levels to determine the dynamic range and the overall contrast within that range. I mention this because I don't understand your term, "contrast range," and more importantly, because perhaps that term is also new to Christina.

[Jeff S]

I agree with virtually everything that has been said in this thread with regards to the levels and curves adjustments. I rarely use levels, but use curves in virtually every image. I do not use the in-camera adjustments very often because post-processing software is so superb these days. (One exception is the white balance, which I will sometimes adjust in camera.)

I use Kelbytraining.com for much of my learning, but also like the Adobe videos (Julianne Kost, especially).

One thing I would add to the conversation which I did not notice anyone mentioning (although I may have missed it somewhere) is that I think it is useful to experiment with each of the adjustment tools as part of the development of "your eye". It's difficult to know what a given tool can do for a photograph if you don't spend time playing with it. Besides, its just plain fun to experiment. These tools are often so sensitive that you don't have to make drastic changes to receive significant results, especially when you begin using several tools in tandem.

[Brownbear]

John, thank you for clarifying and enjoy your time with your fiance. Mike and Jeff, very helpful thank you.

[John Morton]

Based on the helpful explanation that you provided in your first post, I think it's more accurate to say that you are using Levels to determine the dynamic range and the overall contrast within that range. I mention this because I don't understand your term, "contrast range," and more importantly, because perhaps that term is also new to Christina.

Those who are familiar with printing black and white film on photographic paper may recall a time when papers were graded for the contrast range they captured; with "0" for very low contrast images and "5" for extremely contrast. then along came polycontrast filters and paper, where the contrast range was selected through the use of numbered filters which went into the enlarger while printing.

I tend to use Levels in the same way, matching or shaping the extent of the contrast range in the image with the space available in output levels.

[Wayland]

Multi contrast paper was such a liberation back then wasn't it?

The ability to have different contrast grades in different areas was ground breaking at the time. (OK, I know we used to "flash" paper to achieve something similar but it wasn't the same.)

Using layer adjustments and masks is so much more powerful though. I miss some stuff about darkrooms but I wouldn't give up the control we have now.

[Mike Buckley]

I miss some stuff about darkrooms but I wouldn't give up the control we have now.

Never having worked in a darkroom, I have always wondered about that though I have never asked. It seems so obvious to this non-user of darkrooms that the electronic post-processing offers so much more control and without the mess of chemicals. When I think of the mercury vapors that photographers were exposed to when making Dageurotypes (I never remember how to spell that word), I cringe.

[Mike Buckley]

Thanks for that explanation of "contrast range," John. Very helpful!

[jcuknz]

Hi Photo Nut,
Thank you for your reply. I'm truly sorry but I don't understand what you are trying to share with me. Is the idea for me to play with your photo and try out strange curves to learn the effects of the different and odd shapes?

Thank you.

NO ... play with your own photos If you apply the polarisation/sabatier effect more than twice to a photo the colours go all heck. P/S is a fume room technique which we are approximating with the curves tool. This photo has had it done twice .. ie. applying a W curve [ I think it was, a long time ago, May 2003 ] once and then a second time to the result of the first application.
My first example is IMO pretty drack but I quite like this one in retrospect

Straight photo as shot