topic Re: Does this histogram look right? in EOS DSLR & Mirrorless Cameras

Does this histogram look right? R10

albionshire — Sat, 24 Feb 2024 19:58:17 GMT

I've been advised that a good exposure for histograms should be in the middle, what do you think of this? Is it over exposed or underexposed? My issue is if I get the big curve to go in the middle of the picture, it looks darker, the other issue is I'm using a calibrate colour chart and their suggestion is the 4th grey patch should be RGB 128, to get it to 128 there's no way I can get the curve to be in the middle, am I missing something? This current histogram gets me close enough to 128 so does that mean the exposure is correct?

Re: Does this histogram look right?

Danny — Sat, 24 Feb 2024 19:38:35 GMT

Thanks for joining the conversation, albionshire!

So that we can all be on the same page together, please let us know which Canon camera model you're using. That, and any other details you'd like to give will help the Community better understand your issue!

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Thanks and have a great day!

Re: Does this histogram look right?

albionshire — Sat, 24 Feb 2024 19:46:37 GMT

Hey Danny, thanks. Camera is CANON EOS R10, i'm using a 5600k light at 70% capacity.

Re: Does this histogram look right?

rs-eos — Sat, 24 Feb 2024 19:57:17 GMT

Potentially. It really depends upon how the 50% gray swatch on your color checker reads.

e.g. if you bring the RAW file you took into Adobe Lightroom, Capture One, or presumably also Canon's DPP, it should give you some indication as to the luminance or RGB values as you over over the 50% gray swatch.

While I don't have the corresponding histograms in the following post, I did captures of my 50% gray card with my lighting. I adjusted the lighting up/down until the peak in the histogram was perfectly centered on the back of my camera (I only had a single peak since the size of my gray card filled the frame). However, in software such as Lightroom, you can crop in to a particular part of the image representing the gray square to verify where it by itself will read on the histogram. Since your image contains lots of colors and the fabric in the background, it is a bit difficult to see if 50% gray is exactly at the middle. However, it does look good and I feel if any adjustments are needed, it would only be minor (perhaps 1/3 stop more exposure perhaps).

For reference, see the middle section of my post here: Camera and Lighting Experiements - Noise, Exposure, Color

Re: Does this histogram look right?

albionshire — Sat, 24 Feb 2024 20:11:03 GMT

Hi Ricky, as usual thank you so much. Please see the attached image with the 18% gray card (according to calibrite it's 18% not 50%, should I buy a 50% grey card?), is that how the histogram should appear? Also when you say 1/3 adjustment, sorry what do you mean? Do you mean adjustment in increments of 1-3 for either aperture, shutter speed and iso?

Re: Does this histogram look right?

rs-eos — Sat, 24 Feb 2024 20:40:33 GMT

18% Reflectance and 50% (aka Middle) Gray are the same thing.

Thanks for the capture of the larger 50% swatch. Since it appears right in the middle of your histogram, all is well.

In terms of the "1/3 stop" I had mentioned, it was in terms of adjusting the exposure. If working with continuous light sources, that would mean adjusting one of the following: aperture, shutter speed, ISO. 1/3 of a stop is quite small and if you've set up your camera to adjust things in 1/3 stop increments, you'd be able to make those small adjustments. e.g. increasing ISO from 100 to 200 would be a full stop adjustment. But increasing ISO from 100 to 125 would be a 1/3 stop adjustment.

If you're working with flash/strobes, then typically you fix your shutter speed at the camera's sync speed. So to adjust the exposure, you can then adjust one of the following: aperture, ISO or flash/strobe power. Technically adjusting flash power is the best (especially when having to increase exposure) since widening the aperture or raising ISO can also lead to more of the available light influencing the image.

Re: Does this histogram look right?

albionshire — Sat, 24 Feb 2024 20:53:17 GMT

Amazing, thank you so much Ricky! If I make changes to say the zoom, aperture, speed or ISO do I have to re-do the calibrate profile for color calibration?

Re: Does this histogram look right?

rs-eos — Sat, 24 Feb 2024 22:04:45 GMT

You only need to capture an image of the color chart whenever lighting changes (not including flash power).

Examples: If you're using available light (e.g. light coming in from a window) and in the morning, it's a bright sunny day with no clouds. Capture an image with the color chart. If in the afternoon, it becomes a cloudy day, re-capture the color chart since the color temperature of the light from the outdoors is now different.

If using your own lighting though, and you set it up the same way each time, you really only need to capture the color chart once per session. If you move the light around, add a second light, remove a light, etc., then re-capturing a color chart is recommended.

Re: Does this histogram look right?

albionshire — Sat, 24 Feb 2024 22:22:37 GMT

I see, brilliant thank you! One last question, I used the custom white balance setting to take a picture of the calibrite grey card and then used the settings from that to set a custom white balance. If I adjust the intensity of the light I'm using to get a brighter or darker picture for example do I then need to redo the white balance again or can I stick to the same one?

Re: Does this histogram look right?

rs-eos — Sat, 24 Feb 2024 22:44:35 GMT

No. Simply adjusting the intensity of the light doesn't require adjusting the white balance.

Re: Does this histogram look right?

rs-eos — Sat, 24 Feb 2024 22:49:41 GMT

If one of these replies has solved the original question, please mark it as the solution. That helps other forum users know which topics have been solved as well as helping others with similar questions. Thank you.

Re: Does this histogram look right?

albionshire — Sat, 24 Feb 2024 22:54:28 GMT

They all did, to be fair!