FP4 and Anti-halation layers

philldresser · Mar 14, 2004

I predominately use FP4 as I feel comfortable with this film, however I have recently switched developers from ID-11 to Pyrocat-HD. As I develop 5x4 in BTZS tubes it was recommended to pre-soak the film in distilled water, partly to remove the AHL dyes and partly to ensure that the whole negative was wet before adding the developer.

My question stems then from trying Pyrocat-HD on 35mm FP4 which when soaked for the same time yeilds no dyes. So, does 35mm FP4 have AHL dyes like its 5x4 counterpart and if so doI need to worry about getting them out before 'pyroing'?
The negs are slightly different in colour between the sizes with the 5x4 being more 'brown'

Phill

Donald Miller · Mar 14, 2004

Phill,
Antihalation dyes are located on the base side of the film. I don't use 35 mm so I can't say about that film but would imagine that it does have AH dyes too. It may be that the amount of dye to the amount of presoak water may not be as noticeable as sheet film. I presoak my sheet film for 5 minutes in tempered water bath. This does get rid of the AH dyes on FP4 in my experience. The pyro developer works on the emulsion side of the film so the AH dyes aren't involved in film developing. What happens is that if AH dyes are not removed is a build up in general film density that one needs to print through. Depending on the color of the dye, if not removed, may also affect the filtration on VC paper. Good luck.

philldresser · Mar 14, 2004

Don

I also use a 5 min pre soak which takes out the dye effectiively. The water comes out purple, yet the water on the 35mm comes out clear. I can only imagine that they need more AHL due to the extra thickness of the base for sheet film.

Thanks for the reply

Phill

Donald Miller · Mar 14, 2004

Phill,

How do your negs appear? I mean in unexposed and developed areas...if they exhibit normal FB +Fog then I wouldn't concern myself. I don't know why 35 mm would be any different then sheet film. If my memory serves me correctly...it seems that 35 mm used to carry higher FB + Fog then sheet film. But it has been a long time ago and I may be wrong on that.

If Les has a densitometer then he could verify that since he still shoots 35 mm from what I understand.

Ole · Mar 15, 2004

35mm film sometimes doesn't contain anti halation dye, but a tinted film base instead. 4x5" base is often clear, with anti halation dye on the back side of the base. If 35mm film were made this way, there's a high probability of scraping some of the dye off inside the camera.
So:
35mm - no dye,
120 - dye (protected by backing paper)
220 - no dye (at least sometimes)
sheet - dye.

philldresser · Mar 15, 2004

Ole,

That all makes sense and confirms my suspitions.

Thanks

Don,

Regarding the colour and taking into account what Ole has said, the negs on the 35mm still contain a lot of blue undertone whereas the sheet has a definite brown undertone. I dont have access to a darkroom at present but will be interested to see what effect this has on multigrade papers.

Cheers

Phill Dresser

Donald Miller · Mar 15, 2004

Phill,

If you have a blue cast to the film base in 35 mm this would have the effect of increasing print contrast, when used with VC paper.

This is the opposite effect that one would have it a green type stain.

The blue stain you mentioned would have no effect on graded papers and would act only as density.

Hope this answers your question. Good luck.

BobF · Mar 15, 2004

Phil, the Ilford site lists an anti-halation backing for roll (120) and sheet film but none for 35mm. Makes sense as presoak of 35mm pours out clear while presoak of sheet and roll pours out black. I use all three types of FP4.

The acetate they use on 35mm has some kind of tinting that isn't on the roll or sheet film but to me it looks neutral grey, not blue. Densitometer readings on roll and sheet film (FB+Fog) are half that of the tinted 35mm acetate. Readings of .16+/- for roll and sheet versus .32+/- on my old analoge weston densitometer.

Don't ask me why they do this or what affect it has, but if anybody knows please chime in.

Donald Miller · Mar 15, 2004

BobF said:
Phil, the Ilford site lists an anti-halation backing for roll (120) and sheet film but none for 35mm. Makes sense as presoak of 35mm pours out clear while presoak of sheet and roll pours out black. I use all three types of FP4.

The acetate they use on 35mm has some kind of tinting that isn't on the roll or sheet film but to me it looks neutral grey, not blue. Densitometer readings on roll and sheet film (FB+Fog) are half that of the tinted 35mm acetate. Readings of .16+/- for roll and sheet versus .32+/- on my old analoge weston densitometer.

Don't ask me why they do this or what affect it has, but if anybody knows please chime in.

BobF, Thanks for reading the density differences in the differing formats. I thought that I remembered that 35 mm carried a higher FB+fog then sheet film. As I recall the reason that I was given for this is that 35 mm uses a thicker polyester support. The tint that you noted would certainly contribute because it would act as density. The thicker support may be used because the physically smaller film would be more prone to distortion then the larger physical size of sheet film.

BobF · Mar 15, 2004

Don, the base for 35mm is 5mil, for 120 is 4mil, but for sheet is 7mil. I think this means that it has to have some kind of color added to the thinner 35mm base to get the tint.

I was thinking about the blue(35mm) and brown(sheet) color that phil mentions vs. the neutral grey I get on all formats. I use D76 and he was using Pyrocat which I understand leaves a usually green stain. I have never used Pyrocat HD but could this be the difference?

glbeas · Mar 15, 2004

BobF said:
Phil, the Ilford site lists an anti-halation backing for roll (120) and sheet film but none for 35mm. Makes sense as presoak of 35mm pours out clear while presoak of sheet and roll pours out black. I use all three types of FP4.

The acetate they use on 35mm has some kind of tinting that isn't on the roll or sheet film but to me it looks neutral grey, not blue. Densitometer readings on roll and sheet film (FB+Fog) are half that of the tinted 35mm acetate. Readings of .16+/- for roll and sheet versus .32+/- on my old analoge weston densitometer.

Don't ask me why they do this or what affect it has, but if anybody knows please chime in.

They do this to quench the light piping by the film, a la fiber optics. Kodak High Speed Infrared is bad in this respect and it's one of the reasons to load the film in the dark. The other being the felt is not reliable for stopping IR.

philldresser · Mar 16, 2004

BobF said:
Don, the base for 35mm is 5mil, for 120 is 4mil, but for sheet is 7mil. I think this means that it has to have some kind of color added to the thinner 35mm base to get the tint.

I was thinking about the blue(35mm) and brown(sheet) color that phil mentions vs. the neutral grey I get on all formats. I use D76 and he was using Pyrocat which I understand leaves a usually green stain. I have never used Pyrocat HD but could this be the difference?

BobF

In my experience and in the literature from Sandy, Pyrocat usually leaves a brown stain not green. In 35mm FP4 there is a colour shift away from the usual but there is still a blue/grey undertone. In sheet FP4 there is no blue undertone at all. It all comes out in the presoak.

Phill

FP4 and Anti-halation layers

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