setting exposure in post from x-rite colorchecker?

[buckerooni]

hi all, couldnt find a topic on this already, but wondering if it's a reasonable technique to set a 'baseline' exposure using the grey swatches from the x-rite color checker.

is adjusting the exposure in Lightroom until this box's RGB is 50/50/50 a valid technique to get a baseline exposure?



can't find the specs on each color swatch, but assume that this box highlighted in yellow is supposed to be 50/50/50.

thanks for any help.

 

[buckerooni]

Thanks for the feedback, I have controlled lighting via strobes (with no ambient) in the studio and use a light meter. All good!

My question is just about some kind of pseudo empirical in-image technique to check the exposure is 'correct' i.e. not over/not under exposed.

I also see this could be potentially useful if I am matching my studio product photography to lifestyle product shots taken in uncontrolled environments if I slip the colour checker next to the product in-shot, esp. if I know I can't get the desired exposure due to environmental limitations, like a shady spot/dark house etc.

Ultimately I'm trying to remove as much reliance on manual visual/emotional techniques as a starting point of an image for post processing.

 

[knickerhawk]

Thanks for the feedback, I have controlled lighting via strobes (with no ambient) in the studio and use a light meter. All good!

My question is just about some kind of pseudo empirical in-image technique to check the exposure is 'correct' i.e. not over/not under exposed.

I also see this could be potentially useful if I am matching my studio product photography to lifestyle product shots taken in uncontrolled environments if I slip the colour checker next to the product in-shot, esp. if I know I can't get the desired exposure due to environmental limitations, like a shady spot/dark house etc.

Ultimately I'm trying to remove as much reliance on manual visual/emotional techniques as a starting point of an image for post processing.

What you're trying to do with the ColorChecker's middle gray patch is a sensible strategy for normalizing the lightness of different shots. In fact, DPR does the same thing to normalize the lightness of the raw renderings of the Studio Scene shots for all of the cameras it tests. They adjust the Exposure slider in ACR during conversion so that the middle gray patch in the ColorChecker reads middle gray (not sure which value 118 or 119 they're using to set at but it's surely one or the other). Thus, all of the raw renderings in the comparison tool appear at a more-or-less identical overall lightness level. You will note that they don't adjust the JPEG renderings. They spotmeter the JPEGs using the gray patch and let the camera do its own thing for setting exposure and porcessing the OOC JPEG. Thus, you will typically see some variation in the image lightness between JPEGs you're comparing. Far more than you'll see with the raw renderings.

You seem to be a Canon user so here are some illustrations of the foregoing using screen grabs from the comparison tool for four Canon cameras:




Note these raw renderings all read between 118 and 120 in the middle gray patch. Very similar lightness to the images




The JPEG renderings for the same four cameras have significantly different lightness levels. The inner circles above are the corresponding raw lightness levels. I've superimposed them to illustrate just how much variation there can be and why what you're trying to do (and what DPR does for the raws) makes sense if you're trying to achieve a consistent look between different images

 

[Iliah Borg]

Thanks for the feedback, I have controlled lighting via strobes (with no ambient) in the studio and use a light meter. All good!

My question is just about some kind of pseudo empirical in-image technique to check the exposure is 'correct' i.e. not over/not under exposed.

Suppose some important subjects in the scene are darker than that middle gray, and no important subjects are lighter than N 8.5. Do we want the viewer to increase brightness to see into the shadows?

N 5 patch is a guideline only for the scenes that have distribution of tones close to normal. If that's your case, OK. If you are shooting black boots using N 5 as a reference can be problematic.

Studio technique I use is to set light, filters, apply dulling spray and other tricks, and set the exposure to compress scene dynamic range into 7 stops, establishing the midtone in such a way that the shot has the centre of attraction I want while maintaining necessary details in shadows and highlights.

I also see this could be potentially useful if I am matching my studio product photography to lifestyle product shots taken in uncontrolled environments if I slip the colour checker next to the product in-shot, esp. if I know I can't get the desired exposure due to environmental limitations, like a shady spot/dark house etc.

Ultimately I'm trying to remove as much reliance on manual visual/emotional techniques as a starting point of an image for post processing.