Densitometers or scanners and film

[swmcl]

Hello again,

Q1. A densitometer or scanner can scan to 4.0D - correct?

Q2. If a film can't be developed beyond say 2.2D then those digital values beyond 2.2D are unable to be utilised by that film - correct ?

Q3. Therefore if we were to develop film in such a way as to get say 10 zones up to the 2.2D then those 10 zones are spread over the limited digital range of Q2 - correct ?

Q4. To stretch things further, if we were to develop say 13 zones up to 2.2D by using a stand development or some such then in essence, each zone has fewer digital values available to it - correct ?

What I would like is to be able to range the digital scanning from 0 to 2.2D. So that would be say 65536 values over the 2.2D range for example.

I do also realise that Velvia is apparently able to go pretty close to 4.0D. So the scanner and film are 'aligned' in their ranges as it were in this case. Its just the B&W film process I have won't go beyond 2.2D.

Thoughts?

Cheers,
Steve

[Bruce Watson]

Q1. A densitometer or scanner can scan to 4.0D - correct?

Nope. Few scanners can actually scan though 4.0. Indeed, Kodak's test target for density only goes to 3.6, so I'm not sure how you'd be able to verify a scanner going higher than 3.6. Drum scanners can usually scan that deep, consumer flat beds, not so much, no matter what the advertising claims.


Q2. If a film can't be developed beyond say 2.2D then those digital values beyond 2.2D are unable to be utilised by that film - correct ?

The digital values are utilized by the scanner, not the film. The film doesn't know anything about digital values. All the film understands is HSV.

But I think I know what you're getting at. For consumer flatbed scanners, you usually find the the black and white points are not adjustable. I'm not sure about professional flatbeds because I've never used one. But drum scanners usually let you adjust the log amps so that you get the full range of the scanner across just the density range you specify. Even if that's just the range from 0.6 to 0.8 (I scanned a negative like that once for a customer) you can get a scan that "expands" that single zone of density into a full range of digital values from 0-4096 (12 bits) or black to white. Not that people usually want that. But you can do it with a drum scanner if you choose.


Q3. Therefore if we were to develop film in such a way as to get say 10 zones up to the 2.2D then those 10 zones are spread over the limited digital range of Q2 - correct ?

Depends on the scanner, its software, and operator skill.


Q4. To stretch things further, if we were to develop say 13 zones up to 2.2D by using a stand development or some such then in essence, each zone has fewer digital values available to it - correct ?

Again, depends on the scanner, its software, and operator skill.

I know you're looking for a straight-up answer, but straight-up answers are few and far between in photography. But you probably already know that.

[swmcl]

Hi Bruce,

You did give the straight up answer ! Thanks.

The software and drum scanner is the answer (and possibly the more professional flatbed). I'm wanting to know if it were possible to get the full spectrum of digital samples across the full spectrum of the film and you've said, "Yes!".

BTW, which drum scanner are you using ?

Cheers,

Steve