Red #29 filter help please!

[BrianShaw]

The Kodak tech bulletin indicates that 3 stops are for red #25. There is no reference to red #29. But it would seem that additional stops might be required. In any case see pg 5.
http://www.kodak.com/global/en/professional/support/techPubs/f4016/f4016.pdf

Heliopan says 8 - 12x for #29.

Tiffen says 8x

B+W says "appr. 8"

 

[RalphLambrecht]

8x=3stops, log 8/lg2 and 12x= 3.5 stops

 

[Old-N-Feeble]

Filter Factors (depending on film and subject matter)

Wratten #25 approx. 3 EV
Wratten #29 approx. 5 EV

The image you linked to in post #3 appears approximately 2 EV underexposed... unless you were shooting for a stark look with decreased shadow detail.

 

[L Gebhardt]

I like the image a lot, however I do think it's a bit underexposed. Maybe this is the film, and maybe the filter. It's also possible it's just the scan. Look at the shadow areas of the negatives and see if there is any detail in there. Compare this to shadows where you didn't use the filter. If they are the same and without real detail you are simply under exposing. If the filtered shots are less detailed then your filter factor isn't high enough. You probably want to look at more than just a few negatives. When in doubt give more exposure.

I would not push the film (over develop it) to compensate. I'd rather loose the tiny bit of shadow detail you gain than ruin the tonality of the whole image which is what push processing usually does in my experience.

 

[Old-N-Feeble]

^^^ Right, I wouldn't push the film either. Maybe experiment with a compensating developer to increase film speed instead. I have no experience with those but hopefully those who do will chime in with recommendations. If you do try a different developer I suggest you shoot a couple of test rolls under identical conditions and develop those first so you don't lose important images by error.

 

[BrianShaw]

8x=3stops, log 8/lg2 and 12x= 3.5 stops

Yes, pretty consistent guidance... isn't it!

 

[DREW WILEY]

With the specific films he mentioned, 25 and 29 have the same factor. What will differ is the distinctly different shape of the toe between these,
as well as the real-world ASA. Once you get involved in an orthopan film like ACROS, instead of true pan, all a 29 does is lop off a zone or two
in the shadows completely. ACROS just doesn't have sensitivity that far down into the red. With a 25, it requires the same 3-stop correction as
most true pan films. It makes no difference what the mfg of these filters says in any GENERIC sense. Not all films are the same. Since I ordinarily
shoot 8x10 films, often in high contrast mountain and forest settings, you can be darn sure I'm not guessing about any of this. But there is simply no substitute for correctly metering the shadows, testing in advance, and then understanding why two different films of allegedly analogous speed give very different results.

 

[BrianShaw]

So about how much of a difference is the filter factor between films. Can you give me an example, please.