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Photo Forum / Film Photography / Medium format / May 2004film warping in 6x9s
I am very aware that in 6x9 cameras the warping of the film can throw out focussing. I'll be taking some 6x9 shots soon with a rollfilm camera. Is there an optimum time I should leave after I have wound onto the next frame to get a minimum warping? And if somebody can recommend this optimum length of time to leave the film to recover from coming off the spool and moving into place, then is there a feeling for the amount of warping still remaining in decimal fractions of a millimeter? > I am very aware that in 6x9 cameras the warping of the film can throw > out focussing. I'll be taking some 6x9 shots soon with a rollfilm [quoted text clipped - 4 lines] > feeling for the amount of warping still remaining in decimal fractions > of a millimeter? Shoot with a Rapid Omega and you wont have to worry about film warping. To answer your question, .0001mm or see http://medfmt.8k.com/mf/flat.html and http://medfmt.8k.com/mf/critical.html for more math, examples of ranges of warpage, and so on from real world tests and so on.. hth bobm  Signature*********************************************************************** * Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 * ********************Standard Disclaimers Apply************************* > I am very aware that in 6x9 cameras the warping of the film can throw > out focussing. I'll be taking some 6x9 shots soon with a rollfilm > camera. Is there an optimum time I should leave after I have wound > onto the next frame to get a minimum warping? I think that problems caused by the film developing a set are the domain of perfectionists. One big problem with 6x9 folders is that people sometimes open the bellows too quickly. The partial vacuum produced can cause the film to bow outwards, this can cause fairly severe focus problems. Another thing to watch is how well the end of the backing paper is attached to the takeup spool. I like to wrap the backing paper a couple times around the spool and test it under tension before inserting the spool into the camera. Before I adopted this procedure, I used to sometimes find that the film and backing paper were not wound tightly around the takeup spool when I removed it from the camera. If this happens to you, it is a sure sign that the film was not under the proper amount of tension when it moved through the camera, and it probably results in a lack of film flatness in addition to loosely wound spools. Peter. Signaturepirwin@ktb.net a > I am very aware that in 6x9 cameras the warping of the film can throw > out focussing. I'll be taking some 6x9 shots soon with a rollfilm > camera. Is there an optimum time I should leave after I have wound > onto the next frame to get a minimum warping? Depends on the camera. Some don't have this problems, with some it -is- a problem. SignatureStacey > I am very aware that in 6x9 cameras the warping of the film can throw > out focussing. I'll be taking some 6x9 shots soon with a rollfilm [quoted text clipped - 4 lines] > feeling for the amount of warping still remaining in decimal fractions > of a millimeter? I have seen two contradictory recommendations: 1. Wait, till the film has relaxed and flattened out. 2. Shoot immediately, before the tension of the film is lost. Go figure. -- Lassi Lassi Hippeläinen <lahippel@ieee.orgies.invalid> wrote in message news:<409B3028.8FCE4743@ieee.orgies.invalid>... > > I am very aware that in 6x9 cameras the warping of the film can throw > > out focussing. I'll be taking some 6x9 shots soon with a rollfilm [quoted text clipped - 11 lines] > > Go figure. Figuring now.... When you wind on the film it has just gone over a roller and been bent through an angle so I would guess that to take the shot immediately would not be a good idea. But if you leave it in place for too long then maybe it will gradually warp. I'm guessing that a time of one to two minutes after winding on would be best. > When you wind on the film it has just gone over a roller and been bent > through an angle so I would guess that to take the shot immediately > would not be a good idea. But if you leave it in place for too long > then maybe it will gradually warp. I'm guessing that a time of one to > two minutes after winding on would be best. I think you will find that for 99.9% of your shooting it won't make any difference. Like I said before, if flatness is really an issue than use a Rapid-Omega and settle for a 6x7 format. > > When you wind on the film it has just gone over a roller and been bent > > through an angle so I would guess that to take the shot immediately [quoted text clipped - 6 lines] > Like I said before, if flatness is really an issue than use a Rapid-Omega > and settle for a 6x7 format. I can't really settle for that when I already have some 6x9s. This got me wondering. If film bulge is a problem even for the 35mm format (which I am sure we have all heard about here <cough spit>) then why didn't people use the rewind lever to give a bit of extra tension in that strip of cine film every time they took a shot? Surely that would have flattened the film a treat? I always "tighten up" my film when shooting 35mm. 120's a little different as there's tension there from the beginning. I think though that you'd probably get flatter results with 2x3 sheet film in the right holder than 6x9 roll film. > > > When you wind on the film it has just gone over a roller and been bent > > > through an angle so I would guess that to take the shot immediately [quoted text clipped - 14 lines] > tension in that strip of cine film every time they took a shot? > Surely that would have flattened the film a treat? > This got me wondering. If film bulge is a problem even for the 35mm > format (which I am sure we have all heard about here <cough spit>) > then why didn't people use the rewind lever to give a bit of extra > tension in that strip of cine film every time they took a shot? > Surely that would have flattened the film a treat? Somebody i once processed film for used to do that religiously. His films very often showed a strange darkening, a veil, strangely regular but irregularly all along the length of the film, coming in from in between the perforations. They vanished, never to return, when i told him to stop doing that wholy unneccessary extra tensioning. A schoolbook example of stress-veil it was. So beware. When tensioning the film, all you do is stress it lengthwise, the stress concentrating on the bit where the perforations are over the sprocket. I doubt it will help flatten the film, since it's bulge is across the width of the film. I don't do it with every exposure. I do it at the beginning so that the rewind knob moves as I advance the film. I haven't noticed any problems - should I stop? Again with 120 film, you've got tension from the beginning. > > This got me wondering. If film bulge is a problem even for the 35mm > > format (which I am sure we have all heard about here <cough spit>) [quoted text clipped - 14 lines] > doubt it will help flatten the film, since it's bulge is across the width of > the film. > I don't do it with every exposure. I do it at the beginning so that the rewind > knob moves as I advance the film. I haven't noticed any problems - should I > stop? No problems? No reason to stop. But what advantage have you noticed that could be construed as reason to continue? > Again with 120 film, you've got tension from the beginning. Rather limited. What's holding the film taut? A piece of spring metal rubbing against the paper backing. 35mm doesn't even have that. > > I don't do it with every exposure. I do it at the beginning so that the > rewind [quoted text clipped - 9 lines] > > Rather limited. What's holding the film taut? > A piece of spring metal rubbing against the paper backing. 35mm doesn't > even have that. Some 120 camera's also have a "drag clutch" on the feed spool to put some tension on the film. The Kiev 60 does this and some of the 'blad backs do this as well. SignatureStacey > A piece of spring metal rubbing against the paper backing. 35mm doesn't even > have that. 35 mm film has to find its way through the "friction lock" that is the felt lined slit in the cassette. Then there is no room for it to buckle (the slack has to go somewhere) between pressure plate and film gate. And there's that sprocket wheel holding it at one point too. ON Wed, 12 May 2004 19:40:28 +0200, "Q.G. de Bakker" <qnu@tiscali.nl> WROTE: >> I don't do it with every exposure. I do it at the beginning so that the >rewind [quoted text clipped - 5 lines] >But what advantage have you noticed that could be construed as reason to >continue? Late again to this thread, but I don't see an answer to your question, so: I've been doing this for over 40 years w/ 35mm RF's and Slrs. It is what I was taught by a "pro" back around 1960. Could be he just didn't trust those newfangled miniature cameras some press photographers were starting to use (he preferred his Rollei). The idea is not to put tension on the film, but to know for sure that the film is feeding. Beats figuring it out when you get to exposure #40 on a roll of 36! Obviously I do not have a "drop in" auto-loading 35mm if I'm still doing this. > Late again to this thread, but I don't see an answer to your question, > so: [quoted text clipped - 7 lines] > on a roll of 36! Obviously I do not have a "drop in" auto-loading > 35mm if I'm still doing this. The idea to watch the rewind knob rotate when winding never came to mind...? ;-) |
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