View Full Version : Are the whites hot?

Kerry Perkins
04-02-2011, 01:12 PM
One of the most difficult aspects of an image to evaluate (especially with birds it seems!) is the level of the peak whites. Are they blown? Are they not blown but still too hot? There is a lot of discussion about this topic and it is often stated that the viewer's monitor may be contributing to the evaluation. While it is true that monitors often vary (especially if not calibrated frequently), but there is an easy, definitive way to determine the absolute value of any pixel in your image.

There are free applications for both Windows and Mac that let you see exactly what values are being displayed on the monitor, and since they are reporting what is in the file, the monitor becomes a non-issue. You can use this method on a monitor that is horribly mis-adjusted and still be assured that the peak values are what you think they are.

Here is a screen shot of one of my images. You can see that I have the "DigitalColor Meter" (a utility that comes with every Mac - it's in the Utilities folder) open on top of the image. The way the color meter works is that you simply place your cursor over the image and it tells you the 8-bit values that each pixel contains. You can't see the cursor in this screen capture because the capture program doesn't include the cursor (you wouldn't want it to normally), but you can see in the detail window of the meter that I am looking at some pixels that are just to the left of the eye. By looking at these values I can tell that my "whites" are not even close to being clipped (255-255-255) and are within the comfort range. Ideally, I don't like to have any color channel go over 245, and you can see that blue is at 247 but it seems to work ok in this image.

For Windows users there is a nifty free program called "ColorPic". You can download it here - http://www.iconico.com/colorpic/ . I find this little gem to be much better than the free Mac one but it works the same way. (I use Parallels on my Mac to run Windows XP, and I have tested this application.)

Using one of these utilities will take the guesswork and opinion completely out of the equation when evaluating white levels. Since you are looking at what is in the file, the display device has no bearing on the evaluation and you can see exactly what is posted on web sites. As you can see in my example, I am looking at my image on the BPN site and I can be confident that the whites are exactly what I wanted them to be all the way to the end of the process.

This technique is also useful for evaluating color casts. All shades of gray, black, and white are, by definition, combinations of the three primary colors in equal amounts. Colors are always specified as "red-green-blue". Absolute black is 0-0-0 and absolute white is 255-255-255 in an 8-bit image, which is what we post on the web. Neither of these values should be present in your images (a general rule of course), as they indicate a complete lack of detail in those areas. If you are looking at plumage that is supposed to be gray, you should see a reading like 128-128-128 (50% gray) or something similar based on the light level. If you see 128-128-135, you are looking at a bluish cast. This can be very useful and also take monitor calibration right out of the picture, so to speak. It is also an excellent way to verify that you don't have a color shift between your workflow and your web images.

I hope you find this helpful!

Stan Cunningham
04-03-2011, 10:06 PM
I will definitely try that for windows but my problem still lies with not overexposing when pushing the shutter. Lightroom does a pretty good job of showing "clipped" pixels and I'm still frequently humbled.
You "nailed" that Anna's, good job.

Allen Hirsch
04-03-2011, 11:19 PM
Very useful tip, Kerry.

I find it interesting that I could get those red-green-blue numbers in Elements to check for blown whites, but apparently not in full Photoshop.

WIlliam Maroldo
04-03-2011, 11:45 PM
Wait, wait. It has always been available in photoshop. Window/info. The color information shown wherever the cursor is. Also there is a "show clipping" option in curves, as well as the histogram. The big question to me at least has to deal with clipped highlights in RAW files and to what degree they can be recovered. In other words is there useable digital contained within what is indicated as being clipped?Sometimes there is. Clipped highlights that have no digital information can always be reduced in brightness, so they don't appear "blown" in the jpeg, but the telltale sign is when RGB values are the same, such as by using info in photoshop, as you move the cursor across the area. Such as R240/G 240/B240 regards~Bill

William Malacarne
04-03-2011, 11:46 PM

Across the top of PS click on windows, open in the drop down menu click on Info. It will open a window that you can get the RGB numbers plus a few other things. I usually select the eye dropper tool and place it over the area that you want to sample. With the tool over the sample area you can right click and select the size of sample you are checking....such as single point, average of 3, 5....etc.


Kerry Perkins
04-04-2011, 09:41 AM
Yes, this capability exists in Photoshop and Lightroom and other editing programs. The nice thing about these apps is that they show you what is published on a web site, regardless of how it was processed and without any software running at all. I have read many posts that say "it was fine in my editing program, but looks different on this site". If you see that happen, you know you have a problem in your workflow at the very end when the conversion for web takes place. This also allows anyone looking at an image with a web browser to make a determination about the peak whites and neutral colors using a known standard. That is very different from taking a published image, downloading it to your computer, opening it in your editing program, and evaluating it on your system. This method only deals with the picture that is on the web site, which is the final destination for your posted images, and takes all the discussion about PS vs. LR vs. Aperture vs. Elements, etc. out of the evaluation.

John Chardine
04-10-2011, 11:06 AM
I am a fan of the LAB colour space because it separates Luminance (detail) from colour information. Think of your image as a black and white- the Luminance channel- coloured in with the A and B channels. This is very useful for several reasons:

1. Chroma noise is contained in the A and B channels and can be eliminated without affecting detail at all.
2. As all the detail of the image is in the Luminance channel, this channel can be sharpened without affecting the colour of the image (normal Unsharp Mask sharpening in RGB can sometimes produce a colour shift).
3. Clipping of whites and blacks can be observed and fixed in just one channel- Luminance. Although it is pretty simple to look for 255,255,255 in RGB, in LAB you just look for one number around 100. Look for 0 for the clipped blacks.
4. Colour casts can be diagnosed and fixed extremely easily in LAB because by definition, neutral colours (blacks, whites, pure greys) are 0,0 in the A and B channels. Negative numbers in A or B give a cool tone (towards green or blue) and positive numbers give a warm tone (towards magenta or yellow). Casts are fixed by pulling up or down the A and/or B curves.
5. Colours can be lifted and separated using Curves on the A and B channels and produces a much better result that changing the Saturation in RGB.

I encourage people to play with the LAB colour space if you have access to it. The Digital Colormeter Kerry talks about can be set to give a LAB readout (choose CIE L*a*b). Unfortunately Elements does not give you this option. Not sure about Aperture or Lightroom.

I've always wished for LAB colour options in Adobe Camera Raw but they are not there (yet).

Ken Kovak
04-21-2011, 05:29 PM
Yes, this capability exists in Photoshop and Lightroom and other editing programs.

In my version of LR 3.3 the histogram windows shows the RGB values as 0-100%. Is there a way to get LR to show in values of 0-256?


William Malacarne
04-21-2011, 05:52 PM

You can see them in the Develop module below the Histogram as you drag the cursor over a photo.


I guessed wrong...I only get percentages also....

Steven Kersting
04-21-2011, 06:14 PM
Too add my 2c:

There are two places I expect to see true white and true black, highlights and eyes (pupil or dark area if eye is all black). I usually use levels to set these points and then I usually set the white output to 245 and blacks to 10 (reduces contrast a bit and works better for print).

As for color, the example provided looks blueish and a little flat, but that is (probably) largely because I am using a Mac and Safari (a color managed browser) and primarily because the image does not have a valid exif header w/ the color space embedded. (IE won't have this issue)

William Malacarne
04-21-2011, 06:19 PM
I found how why there is not the numbers 0-255.
0-255 is 8 bit and in LR3 we are working in 16 bit......


Ray Rozema
04-21-2011, 10:30 PM
Thanks Kerry for starting this thread and to everyone for their input


Ken Kovak
04-22-2011, 01:35 PM
I found how why there is not the numbers 0-255.
0-255 is 8 bit and in LR3 we are working in 16 bit......



Thanks, of course that makes sense. I didn't take the time to think that through.


Troy Lim
08-13-2011, 10:04 PM
Kerry, thank you for sharing. :) It is a useful tool.

Kerry Perkins
08-26-2011, 07:41 PM
You're welcome Troy! Glad you are finding it useful. :c3: