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slithy · Joined: 07 Jan 2006 Posts: 16 Location: Denver, CO

I have been suspecting that film flatness with my 23 holder might be causing me some problems, and just did a test to confirm it. Shooting a brick wall straight on at various f/stops - f/3.5, f/8 and f/22. At 3.5, the sharpest areas were about 1/4 and 3/4 up the negative. The center was definitely soft as were the edges. f/8 was only marginally better, and f/22 was pretty good, although there seemed to be some "smearing" near the edges.

So, I'm wondering if I can add pin rollers to my 23 holder. I have a RH20 with pin rollers, and looking at the way it is done, it doesn't seem like rocket science. The gate area would need to be widened slightly from the back only, and if I can find some small steel tube and steel wire of the right dimensions, it looks like there is a small groove cut for them, and epoxied in place. (I'm not considering taking them off the RH20 - I would make them new.)

Has any one done this? Any ideas would be welcomed.

45PSS · Posted: Wed May 17, 2006 5:18 am Post subject:

The added rollers would have to be extremely smooth and turn freely to work and not scratch the film. Replacemant rollers for mamiya RB backs can be purchased from Mamiya and should be the right size and type.

Before modifing check supply roll holders tension and only advance the film when ready to shoot the shot.
Charles

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slithy · Joined: 07 Jan 2006 Posts: 16 Location: Denver, CO

Thanks Charles. I'll look into checking the supply tension, as well as the Mamiya rollers. That would be much easier than trying to make my own!

paulownian · Joined: 07 May 2006 Posts: 16 Location: South Central Pa.

I'm curious if simply watching the tension has solved your problem?

slithy · Joined: 07 Jan 2006 Posts: 16 Location: Denver, CO

Sorry, haven't had time to mess with this yet. But looking at the carriage, how do you adjust the supply tension? By bending up the metal "wing" that pushes up on both reels, attached to the carriage in the center? I don't see anything else that would put tension on the supply reel.

Also, I learned that the pin rollers are more complex than I first thought, and I'm really reluctant to try this now.

tsgrimm · Joined: 04 Apr 2004 Posts: 158 Location: SE Michigan

http://www.skgrimes.com/thisweek/9-22-05/index.htm

Hi, I passed on this post a long time ago.

S.K. is adding rollers to the old style backs. Probably pricey, but so are good used lever wound RH-8 backs.

This option extends the usable life and value of the knob wound backs that some people feel are the best of the two styles.

Could be worth an email or a phone call to find out.

Henry · Posted: Sat Jan 05, 2008 1:47 am Post subject:

Knob-wind backs are great, more reliable than lever IMO, since lever-wound backs have a return spring which, of course, the knob-wind doesn't need. Although you *can* use the lever back even if the return spring dies, it's unhandy to do so. I wish all my lever backs were knob-wind---with the pin rollers, of course!

Dan Fromm · Joined: 14 May 2001 Posts: 2134 Location: New Jersey

But Henry, the rollers are attached to the shell, not to the film carriage. There's no reason why you can't put a knob advance carriage in a shell with the rollers.

Henry · Posted: Sat Jan 05, 2008 6:17 pm Post subject:

True, Dan, but what isn't interchangeable is the format! My knob wind is 6x9 ("23"), but my levers are 6x7.

Dan Fromm · Joined: 14 May 2001 Posts: 2134 Location: New Jersey

Henry, could you buy a junk 2x3 lever wind roll holder and reuse the shell?

Henry · Posted: Sat Jan 05, 2008 6:28 pm Post subject:

Yeah, at the next Trevose show if any dealers show up!

Incidentally, my 6x9 "23" knob was an outright gift from an acquaintance in Buck$ County who never used it; it's in LN condition. I've only ever put one roll through it, so I don't even know whether film plane flatness is a problem. That'll be another warm weather project.

Dan Fromm · Joined: 14 May 2001 Posts: 2134 Location: New Jersey

Um, the last Sam Vinegar show was back at Fort Washington. I don't know whether he's changed venue permanently. Second Sunday staggers on with less and less there. Fewer dealers, less goods of any kind and less interesting material. But I did get a perfectly good 2x3 Crown with Graflok and no focusing panel for $10 there a couple of months ago. Brooklyn Camera, Arnie wasn't there to set prices and his troops were making mistakes ...

I'm going to the next one, hope that John Aungst shows up. I need some step rings that he might have. If he comes.

Henry · Posted: Sun Jan 06, 2008 1:02 am Post subject:

Right, it was Ft. W. John Aungst hasn't been at the last couple of shows I attended. When I was looking for steppers he never seemed to have any, nor series 6 stuff either. I got a set of 44 steppers (to 49, 52, 55) a few years ago at the Radison from another dealer; they are marked "Made in India." Don't see these often. Right now I'm not after anything in particular, but I like to see what might turn up. Wayne is too far for me to drive, almost to NYC. Tried it once, took half the day.

Dan Fromm · Joined: 14 May 2001 Posts: 2134 Location: New Jersey

Henry, John A. was there last month.

The step rings I need all go from quite a bit smaller to 52 mm. If need be, can do it in two steps.

I can buy 'em by mail order or, slowly, from vendors on eBay. But given that I'm going to make the trek to Wayne anyway, buying from John will save a lot of postage. If he shows up. If not, some of the other vendors have boxes of step rings and I'll be in for a lot of searching.

camz · Joined: 15 Apr 2004 Posts: 138 Location: Southern CA

I'd like to know if anyone has had a back modified by Grimes.
What's the cost, turn-around time?

Has anyone run film through both types of backs, roller and non-roller, to compare results? There are a lot of factors affecting film flatness, such as the age and temperature of the film.

Mamiya S-type roll-film backs have a very good reputation for film flatness. Has anyone tried adapting one?