Film thickness and LF

[colrehogan]

I received the following in an email earlier today from Maco regarding their new IR film:

isn't 100 micron to thin for 4x5"???

And I don't understand what that means. How would film thickness affect it's use in holders 4x5 and larger?

 

[Nick Zentena]

It's going to move the film plane. Will it matter? Hell if I know. The standard is 0.197 +/- 0.007 from the front of the film holder. I hope that makes sense.

http://home.earthlink.net/~eahoo/filmhold.html

Depth of film surface on the first picture. A thin/thick film will cause that distance to vary.

 

[colrehogan]

Interesting. I went and looked at a couple of various films' technical sheets and found that each format film is a different thickness of base. I never noticed this before.

 

[David A. Goldfarb]

The emulsion is on the surface of the film, so the film thickness shouldn't really matter, as long as it's thick enough to stay in place in the holder.

 

[David H. Bebbington]

Can't understand Maco's decision. 0.110 mm or 4/1000" is, for example, the thickness of the base of HP5 Plus ROLLFILM, whereas HP5 SHEET FILM is on 0.180 mm or 7/1000" base. This sheet film thickness is valuable in many ways - the film will not fall out of the older-type plate/film hanger (with a hinged side) during processing, will not cockle when being pushed into various other types of processing devices and will lie flat in a glassless enlarger carrier or scanner holder. I would also be more confident that this thickness will stay flat in film holders during exposure.

 

[colrehogan]

I do believe they will cut it to size (sorry, I didn't give the whole content of the email before), but his reply suggested he seemed concerned about the film thickness in relation to larger film sizes.

I haven't replied yet since I wasn't sure how important it was. It seems to be quite important.

Here's the whole reply:

In the beginning of the next year we are able to cut the rollfilm
size from a MASTERROLL. In any size. 60mm, 70mm for films and any size for sheet
films.

But........
isn't 100 micron to thin for 4x5"???

I have no chance (absolutely not) to coat the new IR820/400 emulsion onto a thicker filmbase.

 

[Photo Engineer]

Base or support thickness can cause a problem with sheet films. If it is too thin, the film buckles in some types of holder. The old stainless holder that framed the film with metal, or a film clip are the best for these thin supports. A reel tank such as a Jobo will sometimes allow sheet films to slip out due to the buckling.

PE

 

[jandc]

I received the following in an email earlier today from Maco regarding their new IR film:

isn't 100 micron to thin for 4x5"???

And I don't understand what that means. How would film thickness affect it's use in holders 4x5 and larger?

It will work fine in 4x5. The larger the size the more marginal it gets. Maco is only making this in 35mm base and roll film base. They are using the roll film base to make the sheet films instead of having a 3rd coating on sheet film base.

 

[Donald Qualls]

Film thickness moving the film plane?! The film isn't referenced from the front surface, and held in position by spring tension from behind? And for that matter, 100 micron vs. the usual 7 mil is only .003" difference, even if you're referencing from the back of the film. Doesn't seem terribly significant unless you're working at very large apertures.