PS Technique For Checking Exposure (Portraits)

[Eero Makela]

Originally Posted by Benji

All of my old photography teachers touted the same mantra; "get it right in the camera" so that is what I still do.

Benji

I call this "Click, Crop, Post" I am not there yet but at least some of my pics are.

Crop = adding a 4x6 to change the stupid slightly over size of Nikon images (they are not exactly 4x6.

During film and slide days never had PP so had to get it right in the camera.

[kenwae]

Good information, thanks.

[KmH]

Benji you are a veritable fountain of information.

Thank you for sharing your wealth of Portraiture knowledge.

[Benji]

Originally Posted by blumesan

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) ]

Mathematics were never my forte, and according to the experts the f/ stop scale is subject to the logarithmic scale, (I Googled it, and it is still as clear as mud at midnight to me) but according to Benji one third of stop equals approximately 11 points (of underexposure in skin tones.) So I put the Benji scale to the test. I photographed a zebra gray card twice, one at the meter's suggested aperture of f/8 and another at f/9.0 (1/3rd of a stop less than what the meter calls for. ) I then loaded both images into Photoshop and in Info I got a 142 reading on the gray area of the card that was properly exposed and a 127 reading on the gray area of the card that was 1/3rd of a stop under exposed. The eyedropper was placed at the exact same spot in both images. This is 15 points difference. Then I rechecked both readings while holding the eyedropper in the exact same white area of the zebra card. I then got a 10 point difference in the two readings. Then once again I checked my readings in the black areas of the zebra card and I got a five point difference between the two readings.

It appears to me that the 11 figure works best with skin tones but in order to be more scientific I should do the test several more times on a living subject with average skin tones and with several different lenses and different cameras and meters and lights and do it more than one time in a day but for now I think it shows that 11 is in the ball park.

Benji

[blumesan]

@Benji

No question. In this case experience trumps mathematics every time.

I was just trying to set the record straight regarding strict mathematical conversion of the 0-255 scale used by Photoshop to stops. Really inconsequential in this case.

Regards,
Mike

PS Just curious to know how you performed the metering in your test. Hand held meter or in-camera, and if the latter, what exposure mode (matrix, spot, ?)

[tekdiver500ft]

However, this only works with "average" skin tones, or if you don't care about reproducing the tones accurately. You need to get the tones right in the camera to be certain, or have the person available while you edit. A darkly tanned person is going to show maybe 215 to 220 in the highlights, a dark African American will show about 180 to 190, etc. You have to decide if you are trying to produce "realistic" skin tones, "pleasing" skin tones, or "average" skin tones, and go from there.

[Benji]

Originally Posted by tekdiver500ft

However, this only works with "average" skin tones, or if you don't care about reproducing the tones accurately. You need to get the tones right in the camera to be certain, or have the person available while you edit. A darkly tanned person is going to show maybe 215 to 220 in the highlights, a dark African American will show about 180 to 190, etc. You have to decide if you are trying to produce "realistic" skin tones, "pleasing" skin tones, or "average" skin tones, and go from there.

I use a gray card for accurate white balance which gives me perfect skin tones every time. It never lies, and I get realistic and pleasing skin tones. I don't want nor have I ever even heard of average skin tones. The last 10,000 or so people I have photographed I have set the "R" value on the brightest diffused highlight at 240 without any problems. This includes "white" skin, white skin with a little tan, white skin with lots of tan, "black" skin, brown skin and everything in between. In my experience an "R" reading of 215 or 220 will give you dark underexposed skin tones.

Benji

[tekdiver500ft]

In a multiperson shot, then, whose skin do you use? It is extremely improbable that everyone will have the same tonality to their skin, even if they are in the same family. There will be a variety of tonalities, even in a perfectly exposed portrait. Unless, of course, you like incredibly flat lighting.

[Eero Makela]

Originally Posted by Benji

The last 10,000 or so people I have photographed

Benji

If you take 1 person/picture per day every day you have been snapping for 27+ years. I was a math person hehehe


And if you average 100 shots per person that is 1 million shutter clicks or a few shutter replacements or new cameras (my D300 is rated at 150,000 and I think the D3 is 300,000)

==
PS I forgot, I read/heard somewhere that we are all pink inside

[Rodeoshooter]

Benji,

I got readings of 244 and 9 (4 on her left eye) on your image! Is this due to the screens? Shouldn't be, it should be the same on every computer.