Expose to the right - RGB

[jgaddy]

On cameras that can display the RGB histogram, I will assume that you should use the RGB display to get the fist color channel as close to clipping as possible? Correct? Most of the expose to the right rules only use the luminance histo as the example....

Thanks

[engstrom]

Originally Posted by jgaddy

On cameras that can display the RGB histogram, I will assume that you should use the RGB display to get the fist color channel as close to clipping as possible? Correct? Most of the expose to the right rules only use the luminance histo as the example....

Thanks

You are correct. You really want to keep from blowing any of the color channels but you do want them as far to the right as possible. A friend of mine with a 10D kept wondering why some of his portraits looked like the subject had plastic skin. He checked his luminance histo and wasn't blowing it off the right. Turns out he had blown one of the color channels and that didn't show up on the luminance histo.

[jgaddy]

Originally Posted by engstrom

You are correct. You really want to keep from blowing any of the color channels but you do want them as far to the right as possible. A friend of mine with a 10D kept wondering why some of his portraits looked like the subject had plastic skin. He checked his luminance histo and wasn't blowing it off the right. Turns out he had blown one of the color channels and that didn't show up on the luminance histo.

Ok, so here is a followup question to this question. Now that we have established that we don;t want to blow any channels but get one or all of them as close tot he right as possible....Let's say we are shooting something (especially with Canon's) that has a lot of red in it it. The red channel is going to lead way out in front of the other channel. From the Luminance seems very low....What is the easiest way to get luminance levels up without getting are real artificial look. I am talking in post of course. I will say that getting the read channel. in this example, just from clipping as doing everything that can be done in camera....

Thanks

[wyatt]

I'm guessing, but something to try. Convert to LAB, up the levels, or maybe curves, on the L channel. I'd like to know what results you get if you try it.

Wyatt

[engstrom]

Originally Posted by jgaddy

Ok, so here is a followup question to this question. Now that we have established that we don;t want to blow any channels but get one or all of them as close tot he right as possible....Let's say we are shooting something (especially with Canon's) that has a lot of red in it it. The red channel is going to lead way out in front of the other channel. From the Luminance seems very low....What is the easiest way to get luminance levels up without getting are real artificial look. I am talking in post of course. I will say that getting the read channel. in this example, just from clipping as doing everything that can be done in camera....

Thanks

If the red channel is close to blowing then the picture, as seen by the camera, doesn't necessarily have high luminance levels. If you want to up the other levels in post then you could just work with the green and blue channels in post.

[jgaddy]

Originally Posted by engstrom

If the red channel is close to blowing then the picture, as seen by the camera, doesn't necessarily have high luminance levels. If you want to up the other levels in post then you could just work with the green and blue channels in post.

I have tried it before, that is why I am asking.....I usually do more harm to an image than good in post. That is why I am always trying to improve in-camera because if it is left up to me in post, the delete button is usually in the mix....

The is someone on this board that really know how to get good results by raising luminance in some many without killing color....I would love to hear it...

Thanks

[tjavery]

It's been my experience that when shooting a scene with a lot of reds (like a sunset, for example), exposing to the right ALWAYS leads to blowing the red channel. This applies to cameras (like mine) that do not display separate histograms for the R-G-B channels.

I've just begun some experimenting, but it looks like the red channel is safe if you expose approximately 1 full stop FROM the right (1 stop is about the first vertical line to the left of the right edge on the camera's histogram) in this type of situation (overpowering reds).

[evil4blue]

It's not just Canon, Nikon also shoots blazing reds. I think most digitals have a propensity to over blow the red channel.

What I've found is that getting a good present WB will help equalize the channels, thus exposing all the channels to the right is much easier.

Remember, certain situations require that the red channel lead the way no matter what(e.g. sunsets). Also, certain lighting just doesn't have a full spectra of all 3 channels (e.g. incandescent has very little blue). If you WB correctly, and keep the special case lighting in mind, it becomes a lot easier to fully saturate all the channels.

One more thing to keep in mind, there are 2 green pixels for each red and blue pixel. Your camera will artificially boost the red and blue by a factor to help equalize the channels. Since there is naturally more red light in the world than blue and the red channel is then multiplied by this boost factor, reds tend to reach blown status much quicker than the other channels. This boost factor is also the reason why the blue channel tends to have more noise than the other 2 channels. There is so little blue light, especially indoors, that the camera really boosts the blue channel, thus increase the noise level.

There has been an interesting article over at nikoncafe and dpreview about using colored filter to bias the sensor into recording fully saturated color channels without boosting the red and blue channel. Some of the sample images show an increase in dynamic range and a decrease in shadow noise.

[tjavery]

Originally Posted by evil4blue

There has been an interesting article over at nikoncafe and dpreview about using colored filter to bias the sensor into recording fully saturated color channels without boosting the red and blue channel. Some of the sample images show an increase in dynamic range and a decrease in shadow noise.

Could you please post a link to that? Sounds very interesting.

[evil4blue]

Nikoncafe:
http://www.nikoncafe.com/vforums/sho...ighlight=cc40m

dpreview:
http://forums.dpreview.com/forums/re...ssage=17142860

[tjavery]

Thanks!