How can MF bring greater resolution, don't diffraction limits apply?

[Roger Krueger]

On the contrary. With film, exposure times cannot be allowed to grow too long. The reciprocity of extending exposure duration to compensate for lower light levels at the image plane, breaks down, and the film loses sensitivity. This is called Reciprocity Law Failure.

It isn't just a loss of sensitivity, which is inconvenient enough, because you CANNOT fix it by simply giving longer exposure times, of course....

Sure you can. For normal (non-Tmax) negative films adding a half-stop for every metered stop over 1 sec. is almost always close enough.

Slide film with no margin for error needs to actually use the spec sheet, but it's still usually in that range.

The only film I've seen with failure so bad that adding time didn't work perfectly was Polaroid pos/neg.

but it screws up the colour as well, because the three layers in the film are not affected equally by Reciprocity Law Failure....

It screws it up fairly modestly, but in the slide-film world of no margin for color correction you did have to filter.

.... and the use of colour correction filters doesn't help, either.

Sure it does. That's why slide film spec sheets included filtration specifications in their reciprocity tables.

They further reduce the light entering the camera.

Trivially. It's nowhere near as big a color shift nor light loss as the two-stops-for-tungsten that's all most folks have ever filtered for.

It is a lose-lose downward spiral situation. The only way out of the cycle is to add more light .

Completely wrong.

The failure of Reciprocity Law doesn't happen with digital, which is a blessing, but with long exposures we tend to get noise instead.... (which could be considered analogous to loss of sensitivity, since we also get noise when underexposing.)

No, with digital long exposures you get noise even when your exposure is perfect.

Seriously, medium-long night exposures are the one thing I still prefer film for. Most situations patience is all you need to get around reciprocity failure. Noise and stuck pixels in digital long exposures are impossible to completely fix.

 

[Barrie Davis]

On the contrary. With film, exposure times cannot be allowed to grow too long. The reciprocity of extending exposure duration to compensate for lower light levels at the image plane, breaks down, and the film loses sensitivity. This is called Reciprocity Law Failure.

It isn't just a loss of sensitivity, which is inconvenient enough, because you CANNOT fix it by simply giving longer exposure times, of course....

Sure you can. For normal (non-Tmax) negative films adding a half-stop for every metered stop over 1 sec. is almost always close enough.

Obviously you haven't used 32-ASA Type B Ektachrome, process E3.

Nominal speed back then was 32, but batch variation was considerable. Oftentimes we'd get some at 16-ASA that lost a further 2/3rds stop at 5 seconds, and another 2/3rds stop by 30, with yet another loss to CC filters trying to straighten the colour out.

That is what you call a downward spiral, Trust me.

snip.

Seriously, medium-long night exposures are the one thing I still prefer film for. Most situations patience is all you need to get around reciprocity failure. Noise and stuck pixels in digital long exposures are impossible to completely fix.

And my Lunasix Pro meter had 8 hours as a maximum metered exposure on it... but I had it from a Kodak chemist that were an 8 hour exposure ever actually metered, correction for Reciprocity Failure would ensure the photographer wouldn't LIVE to see the end of the exposure. Apparently, and according to him, the correction would be 84 years... (plus the 8 hours, of course.)

We can agree about Polaroid's lousy reciprocity characteristic, though. Any idea of using it as an exposure guide where flash was mixed with, say, 5 seconds of ambient... was doomed to utter failure.

One of my first uses of alittle digicam was as a substitute for Polaroid tests. It was a great deal more accurate.
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Regards,
Baz

"Ahh... But the thing is, they were not just ORDINARY time travellers!"