Filter transmission curves

That is interesting. Can you repeat these test with sunlight? Additional filters?

Steve

 

Many standard filter curves from Wratten and B+W filters that I've seen also show the high transmission in IR. Most films drop off in sensitivity very quickly after 650nm or so, which makes the filters effective within the spectrum of the film. I suspect it would also be much more expensive to produce filters that block IR (unnecessarily in the case of most films) in addition to the visible spectrum.

Lee

 

Interesting variation in amplitude for each of the filters. I would have expected them to be a bit closer. Of course, the source contributes to the variability of the curves.

I would be very interested in the UV filter response and matching that response to respective manufacturers. I know some are quite good at blocking UV and some are awful!

Thanks for the information!

-Fred

 

If you have a spectrometer, the kind of thing I'd like to see is processed B&W film transmission spectra. Like we have all seen that certain films are more blue or pink after processing. Interesting to see the magnitude of that film base tint. Also, how about stained negatives...would be interesting to see how the spectra differs for different types of staining developer.

 

Easliy done.

Here are the spectral sensitivities of Ortho, Pan and IR films.

PE

 

Ron, I don't think ic-racer means the spectral sensitivity. I think the question is motivated by concern about the UV transmission of the film stain and base, which is especially important for alt printing.

 

Keith;

Yeah, I goofed. Sorry. But all of the films have some degree of UV protection except the newest B&W that Kodak designed for alternative printing.

Thanks. I read that one with my brain somewhere else.

My bad.

PE

 

Just as an addendum to the last post, Keith, a film's transmission spectrum before exposure is equal to its measured spectral sensitivity (absorption) after exposure. This should help when comparing with what I posted above.

PE

 

What if you use a staining developer?

 

Then you add in the relevant stain. I left that out as I have seen stains that range from yellow through brownish to green. But you are right in that case.

PE

 

Actually I was thinking more along the lines of Blue and Green transmission and MG printing. Kind of to confirm or refute the idea the a different film bases or stained negatives would need a different calibration tables for MG printing.

I currently don't use staining developers because of real or imagined effects on MG printing. Would be interesting to see the magnitude of the mired shift of pyro negatives. Or, more practically, how many CCs of (yellow or whatever) the stain adds to the system.

 

There have been threads on MG printing of stained negatives IIRC. Since I don't use that method, I have pretty much ignored them. You see, the stain is a dye, and that dye like all dyes, will fade eventually. So a stained negative is a moving target over a certain period of time. IDK if anyone has measured it or quantized it.

But, it is not one of my favorite fields.

PE