Question about histogram in RSE

Still new to RAW I am learning many things. I love Raw Shooter Essentials for these images but I don't understand this histogram.

When making adjustments the histogram will change, obviously. There is a small BLUE GREEN RED box on both ends of the histogram. Sometimes only a couple colors appear, sometimes none, or all 3 on one end are blank while the other end has all three lit up.

What do these boxes represent and should I be adjusting it so that all 3 colors are appearing or none? Not sure what it is telling me.

Thanks.

As you move the exposure compensation slider to the left, you will see more and more shadow pixels becoming clipped. As this occurs the clipping may occur first in the blue channel of the pixels - that lights up the blue square on the shadow side.

Conversely, when you move the compensation slider to the right and the highlights begin to clip, you will see one of the three boxes at the highlight end light up indicating which channel starting clipping in the highlights first. Severe clipping at either the shadow or highlight end will probably light up all three channel indicators at that end.

In other words, those little square indicator lights will be the first indication of the onset of clipping. When they are all turned off, there is no clipping occurring at either end.

Wow, you learn something every day, thanks Bob!

Thanks Bob, great explination. What does "clipping" mean technically and in laymens terms?

Blown highlights or completely black shadow (RGB values 255, 255, 255 or 0, 0, 0 respectively).

If I may expand a little on Jeff's explanation - in this context RSE's clipping indicators in their histogram are a little more discriminating than that.

Any pixel tha has even one of its three channels reaching the clipping point will trigger the corresponding colored indicator.

By way of background material necessary to understand all aspects of this, we have to learn a little about the 3 color channels (red, green and blue).

In order to signify a color, such as red, in terms of its relative strength in the form of a number, we assign values from 0 to 255 with zero being none of that color (the absence of any color is darkness or black) and with 255 being the highest possible value (brightness) of that color.

If moving a control, such as the exposure control would change a color to a value above 255 or below zero, we simply clamp or limit that value to the 255 value in the case of highlights or to 0 in the case of shadows, and we call that clamping or limiting "clipping".

So, in the RSE histogram, the little red, green or blue light comes on when you clip a corresponding channel's value at either the shadow end (0) or at the highlight end (255).

Why does anyone care about clipping? Well, if one or more channels are clipping, then the information content is reducing. We are actually removing information that would otherwise be translated into image detail. "Clipping" is the same as taking a napkin with a floral design painted on it and putting it into a dish of Clorox and bleaching out the color.

You're right, and you're wrong...It's John, not Jeff, and yes I was describing "clipping" as in clipping in all three channels. Generally speaking, many refer to clipping as a general term for all three channels, and refer to "clipping in the red channel" for just that. But yeah, your more specific answer is right. In a slightly related theme, you can see what pixels are clipping by clicking the warning /!\ icon. I actually think this feature is a little bit of a let down, because unlike ACR, it doesn't show you what channels are clipping - you left to interpret the histo yourself. Thanks for clarifying, Bob.

Thanks to both of you. This helps me tremendously.

Yeah, but that does not answer the question of who is Jeff. There is someone on the forum with whom I've chatted named Jeff - I must be losing it!

LOL...your great knowledge and willingness to share more than makes of for the lapse.

SOunds like you should do a Q&A thread Robert - seriously!

One thing to also be aware of is that clipping the highlights (or shadows for that matter) is not always a bad thing. There may be times when you want to have a very bright or very dark area. Perhaps a glint in the eye or something like that. Just don't panick when you see the clipping highlights but certainly be aware of where the histogram shows they are clipping and that you want the area to be bright/dark.

It takes practice but as you use the Histogram it becomes easier to understand as you compare the differences in your image.

There are a number of good books that go into a lot of detail about converting RAW images and using the Histogram. These will help you get the most from your images.

cheers
Jim

EOSAddict wrote:
SOunds like you should do a Q&A thread Robert - seriously!

Thanks, but I make enough blunders when I get to pick my topics

Yeah, I know enough about the histogram to know I don't know very much.

The particular image I was working on was a sunset, with a very bright sun and some dark shadows in the same image. It was kind of hard to balance it but sometimes trusting the histogram seems better than trusting the eye ball.

This is my first image I have ever sent away for a large print (20X30) :
http://photobucket.com …rrent=IsleofWig​htcopy.jpg

Not sure if it will print too dark or light, hopefully it's just right. The added "clipping" indicator in the histogram is a nice feature of RSE, thanks again for the explanations.

Nice pic i bo. Its the sort of pic which is almost certain to have higher dynamic range that your cam can cope with, and to be honest, it doesn't matter. It would look odd if you lightened the shadows too much...