I gotta get this thing about Light off of my chest

Why do cameras talk stops, monitors talk contrast ratios, and pictures talk about bit depth? Don’t get me started on f-stops vs t-stops.

Your Friendly Neighborhood Insomniac,

Actually, monitor brightness is measured in nits.

Your friendly neighborhood nit-picker.



But nits are a recent HDR thing. right?

I think they predate HDR, it’s just that it’s a more important rating for HDR so we hear it more often now.

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FYI, @greg you’ve just been granted the Nit-Picker badge. It’s a special badge passed out for anyone making jokes or puns about nits.


I haven’t figured out the custom badge icons yet, so, in meantime, you get an apple icon. As in, nit-picker, picking apples, apples.


Stops are used for cameras because light levels are relative (faster film, slower shutter, larger aperture: things are brighter) and exponential. “this is sixty five thousand times as much light” versus “this is sixteen stops brighter”. They are a very simple way to communicate the vast and relative scale of brightness in the natural world. Opening up a full stop in candle light has the same perceptual effect as opening up a full stop in sunlight.

Contrast ratios seem to largely be a way to say, “this flatscreen isn’t shitty.” I don’t remember anyone bragging about CRT contrast ratios. Nits are a granular, science-y version of stops (they are a linear measurement vs stops being logarithmic).

BIT DEPTH, well shit, frankly I agree that much of the bit-depth discourse is misguided. the ONLY thing bit depth affords you is less image banding. 10 bit log is perfectly fine for basically everything*.

now there’s a sub-catergory here: integer vs float. Floating point files will allow values above 1.0 as well as negative values, but that isn’t specifically tied to bit depth. You could make an 8 bit floating point file, it just wouldn’t be all that useful because it would band like crazy.

*by “basically everything” I mean acquired or generated images that are for video display or film-out. It is useful to convert these files into 16bit float files for comp.


F-Stop measures the aperture size, T-stop measures the actual light passing through the lens. So a lens with a lot of elements may have the same aperture opening as a simpler lens and thus have the same F-stop, but it will let in less light so it will have a higher T-stop number.

It was a bigger deal in the film camera days because you had to meter the light with a light meter, then set the aperture to the right exposure and wouldn’t know till tomorrow if you got it right. Being off by 1/2 a stop could be a problem. Nowadays with the attached HD monitor and it’s helpful histograms you can immediately see if you’re a little underexposed.

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I’d like to nominate @greg’s nit post for “post of the week”.


Nominated. Winner!!


And to add to that, the F-stop is also relative to the focal length of the lens. It is the ratio of the Lens aperture diameter to the focal length.


If you are going to lie awake contemplating things, why not contemplate the difference between Opacity and Transparency? And do all modules actually conform to the same rules? Food for thought . . . .

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f stop is a formula whilst t stop is a measurement. go figure.

or burn and dodge. which one’s which?

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I’ll be thinking about this all day tomorrow as I flip back and forth between Flame and After Effects.

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And that’s my point @Quinn! I’m not smart enough to be thinking of the PROCESS whilst doing something, I need to know the RESULT it will help me achieve.

When you order off the menu at a restaurant, the menu is a list of RESULTS, not processes.

Whats your trick? I cant seem to get any Adobe product to launch on the first try.

Nope… been around for a while. Then there’s ft-lambert projection folks.

And let’s not forget that lights are referred to by watts.

Yay, eleven million tutorials on YouTube and Not a single one answers that question…

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Hey @randy (a bit off topic, and yet) I wish I could give you complete bulletproof rep steps, but after much gnashing of teeth I can now launch photoshop without issue and after effects with only an agonizing pause. Premiere won’t launch at all, unless I’ve freshly rebooted. The creative cloud desktop app mostly doesn’t work at all.

As it sounds like we have similar rigs, I’d be curious to know what you’ve tried.

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