PS Technique For Checking Exposure (Portraits)

[Benji]

If you want to check to see if an image is properly exposed in the highlights and the shadows use this Photoshop technique.

Open the image and grab the eyedropper from the tool box, then go to the top of the screen and click on Window then scroll down to Info. A box will appear. Hover the eyedropper over the brightest area of skin (usually a reflection of the main light on the cheek or forehead) and read the "R" reading on the left side of the box. If it is between 236 and 240 the image is properly exposed. If it above 240 it is overexposed. If it is below 236 it is underexposed. There are 32 points in one stop, so if your reading was 225 in the brightest area of skin you are 1/3rd of a stop underexposed (236 minus 11 = 225. One third of 32 is 11.)

To check for underexposure, hover the eyedropper over the darkest shadow that you should have detail in. In a woman with long hair this will be under the ear on the shadow side of the image. This reading should be between 12 and 32. If it is below 12 it is underexposed.

In the example image below, the brightest area was at the black circle on her forehead and it measures 240. The darkest area was under her ear and hair on the shadow side of her face and the area inside the white circle measures 15.

To check this for yourself right click on this image and highlight "Save Picture As" then note where the image was saved to and the name (INFO) then open it up in Photoshop.

Benji

[12stones]

This is an excellent tool, Benji. Thanks for sharing!

[Lee4145]

Good info Benji.

To check this for yourself right click on this image and highlight "Save Picture As" then note where the image was saved to and the name (INFO) then open it up in Photoshop.

To do this without saving it just right click and hit 'copy'.

Then in PS hit ctrl N and enter.
Then ctrl V and you'll have it open in PS ready to look at.

[loeee]

Benji, does this vary at all with different complexions? In a group with "brown" people and "pink" people, will this still work?

[TAFNAP]

Thank you Benji, I knew I read this before for some reason I thought it was much more complex. But this will work perfect thanks again for your patience and guidance.

[gsk]

Thank you... How can you correct it in Photoshop without going into ACR or Lightroom. Sorry for the stupid question.

[Benji]

Originally Posted by loeee

Benji, does this vary at all with different complexions? In a group with "brown" people and "pink" people, will this still work?

"Pink" people are the same. Brown people is a little different. We still need the 240 in the highlights, but in dark skinned people we should light them so light reflections are used to show the form and contours of the face not shadows. A dark shadow on dark skin only makes the skin darker which will not show form and contour.

Benji

[Benji]

Originally Posted by gsk

Thank you... How can you correct it in Photoshop without going into ACR or Lightroom. Sorry for the stupid question.

While I'm not sure, I don't believe you can. You can make the image appear to be properly exposed by using levels and curves, but an improperly exposed image will never look as "correct" as one that was properly exposed to begin with (or at least on photographic paper.) You Photoshop experts reading this may want to correct me on this. (Of course I'm not talking about 1/3rd of a stop corrections in Photoshop but rather 3 stop corrections.)

I shoot RAW and use a hand held meter so I very very seldom screw up so badly that I need to make huge corrections in ACR, and I NEVER make exposure corrections in Photoshop, so I'm hardly an expert. All of my old photography teachers touted the same mantra; "get it right in the camera" so that is what I still do.

Benji

[Not4wood]

Great explanation, Benji.

On the sample shot, if your exposure in the numbers is correct why does the image appear slightly too Dense? Or is it my Monitor?

I posted a couple of Portraits in the Thread about the Noise and one of them is slightly Dense as well but the whites of her eyes are bright and theres plenty of detail as well.

[blumesan]

Originally Posted by Benji

There are 32 points in one stop, so if your reading was 225 in the brightest area of skin you are 1/3rd of a stop underexposed (236 minus 11 = 225. One third of 32 is 11.)
Benji

Benji-
I certainly am not qualified to question the method you propose to determine if an image is properly exposed. However I must question your method of converting the measured (eyedropper) readings into STOPS. Assuming the 0-255 scale covers 8 stops, the stops are not equally divided into eight intervals of 32 points each. The increment in stops is based on a logarithmic scale. One full stop below 255 would therefore show a value of 128. A reading of 225 would thus compute to 0.186 (~1/6) stop underexposure. A 1/3 stop underexposure would give a value of 203. [ 2^(8.0 - 0.333) ]