6x12 re visited

[bglick]

I am in need of a 6x12 roll film back..... I am curious, since 00 when i researched this last, is there any full 120mm long backs, other than Linhof? I would buy the Linhof, however, the reverse curl bothers me. Does the new Sinar Vario measure 120mm? Da Yi back? Cambo? (which seems to produce zero reverse curl) TYIA

[Bob Salomon]

"however, the reverse curl bothers me"

Why? No one who has purchased one has ever complained or - for that matter - even mentioned it before.

It holds the film flat. That in itself is difficult to do with a 56 x 120mm image.

[bglick]

Bob, I do admire your committment to defending your product lines, at any cost.....

In regards to film curl from the roller, you wrote.......

> Why? No one who has purchased one has ever complained or - for that matter - even mentioned it before.

Never mentioned it before? You may want to run some internet searches on this subject matter.... I remember several mentions of this...

Bob, as much as I admire Linhof quality, there is an inheritent flaw when you put the film rollers behind the exposure area, i.e. the film has to make a reverse curl. Film is sensitive to this sharp bend, and has some memory when the film is left in the back for a very short period of time. When advancing the film, this memorized curl reduces film flatness for that area of the exposed film. If you shoot all your exposures fast, of course, this is not an issue. Of course, this issue is not unique to Linhof film holders. Many other RFB's suffer the same, some to a lesser extent. Of course much of this is somewhat dependent on what f stop you shoot at. At f32, then the problem is less noticeable. If you shoot at f8, the issue becomes of greater concern as the Depth of Focus at the film plane falls within limits whereas the memorized curl will effect focus.

As with everything in photography, it's all about trade-offs. To rid this film curl, and produce a straight path from the supply roller, the film supply spool must be positioned forward of the exposure area, which makes the overall design large and bulky. I do beleive one of Linhof's RFB is designed like this, as well as Sinar and Cambo. Of course Mamiya 7 cameas took this to a new level with perfectly straight film path, and the images reflect such. The Linhof 6x12 back with film rolls behind the exposure has produced a very small compact product, in many cases, a very valuable feature. In many situations, it would pay to just waste one shot if the film was in the back too long, i.e. >10 minutes. In my case, this would produce a lot of wasted film as I rarely fire an entire roll at once. I tend to shoot shots spaced out, i.e. 30 minutes apart.

Ziess once studied this and wrote some long papers on the subject.... here is some of the synopsis of the papers.....

The article goes on to blame rollers in medium format magazines for causing a "bend" in the film and suggests a roll of film be shot quickly before each frame has had a chance to take a "bend" at the rollers.

No doubt, Zeiss which supplies some of the best medium format lenses made today, and to Hasselblad, Rollei and Contax, is having the same problem that Nikon had when they supplied fine lenses to early Bronica cameras.

The lenses may be excellent and test well in the lab, but when used on the cameras, due to film un-flatness, do not deliver the sharp photos they should be capable of, especially at wide apertures.

Now, taking off your Linhof hat, what do you think?

[martin_4668]

I both stock the Linhof and the Horseman. The Horseman is actually a very good rollback - even at 1/3 of the price of the Linhof.

[Bob Salomon]

Bill,

Mentions are from people who actually own a Technorama 612 or a TechnoRollex or a Super Rollex who have ever called and had a problem with film flatness or curl due to the rubber roller.

There are none. No one has called or sent us a problem due to this. People discussing the theory of the problem without experience with the equipment is a moot point. The roller is not a problem. Especially in a camera back that only takes 6 shots on 120 and a whopping 12 on 220.

If you are going to shoot 2 shots a month and then process a 220 roll you might have a point. But 6 or 12 shots go awfully fast, especially if one is bracketing exposures. If you do a 3 shot bracket you get 2 scenes per 120 roll. Film doesn't stay in the camera that way. OK just do a 2 shot braket? Then you get 3 scenes per roll.

As for Zeiss - Linhof is no slouch when it comes to the history of ultra fine camera production either. And they do have an optical department that is no slouch either that has worked for decades with Zeiss, Schneider, Leitz and Rodenstock as well as with companies like Wilde that you may not be as familiar with. Like Zeiss Linhof has manufactured cameras for areial as well as for close range photogrammetry.

[Bob Salomon]

"The Horseman is actually a very good rollback - even at 1/3 of the price of the Linhof."

Martin,

Linhof Techno Rollex has a 56 x 120mm image area. That was what Bill was looking for. Does anyone else have a 120mm long image area? Horseman is somewhere between 111 and 112mm long. A good bit shorter then Linhof's 120mm.

But yes the horseman is a good bit less expensive. perhaps because it can't cover 56 x 120mm.

[David A. Goldfarb]

I don't own a 612 Techno Rollex, but I've owned a 6x6 Rollex, and I have a 6x7 Super Rollex, and I get better film flatness in my Linhof rollfilm backs than in any medium format back or camera I've used. I think they've managed to address the reverse-curl issue simply by using larger rollers than other cameras, which they can do, because there is more room in a 4x5" rollfilm holder than in a back on a medium format camera, and because they are just more heavily built than other backs.

I have a Da Yi 617 back, which doesn't have the reverse curl, and which is astonishingly good for its simplicity and cost, but it's nowhere close to being in the league of a Linhof back.

[Frank Petronio]

Those super expensive Alpa 6x9 cameras can use any roll film back but they recommend the Linhofs for optimal results. Considering that Linhof is their competitor, it's high praise.

I'd buy a used Linhof over a new Horseman anyday. I used to use Wista/Horseman 6x9 backs and they were just OK.

[Stan. Laurenson-Batten]

Why can't manufactures of film backs be honest, or do they have a real problem reading a ruler. Both my so called, six by twelves are little more than, six by ten and a half....

[Bob Salomon]

Stan,

Linhof has always said that their back has a 120 mm long image area and they were the first of the backs that are available today.

Some manufacturer's have been honest.

If you check the magazines morgue files you will find that every press release that has ever appeared for both the three different versions of the Linhof Technorama 612 as well as for the Techno Rollex has always pointed out the larger film area.

[bglick]

Your points are well taken Bob..... maybe this question will resolve the issue. What is the length of the blank spacing between the exposures? It's possible, Linhof designed the back so the curl (or potential curl) resides in this area?

I am curious, what is the greatest angle the film is subjected to in the 180 degree U turn in its journey from supply roll to exposure area? Also, I would assume 220 film would be less prone to this issue as there is no paper backing? Has anyone every experimented with this?

Also, I do beleive both your 6x12 and your 6x17 camera bodies have no reverse curl, as they have positioned the film forward of the exposure area, creating a perfectly straight film path. Isn't this correct? If so, the potential problem does not exist with this design.

Bob, I have used many roll film backs with reverse curl rollers. When I test them by leaving film in for 20 minutes, then advance the film, I can clearly see and feel the film buckle from the roller in the exposure area. I have never used a RFB that forced the film a full 180 degrees like the Linhof 6x12 does. So, if you use the same film, and a similar or more intense roller angle, I just can't fathom how this buckle would NOT be present. I know you can mitigage the problem a bit by shooting at higher f stops, but in my case, this is not possible.

[Bob Salomon]

We will be setting up the PhotoPlus Show in NYC next week and will not be able to do any measurement tests. You can call Marflex at 973 263-5267 and see if he can. Or you can call us at 800 735-4373 to run a roll through or you can run a film if you are at the show - we would need to know tonight to bring the demo back to the show. This is not a specification the factory publishes but Marflex may have it as a repair spec. You can also email Marflex@aol.com.

[bglick]

> We will be setting up the PhotoPlus Show in NYC next week and will not be able to do any measurement tests. You can call Marflex at 973 263-5267 and see if he can.

I will email them....the problem is, this test takes some time to accomplish, you need to try it with 120/220 and then leave film for different durations of time. Ziess estaimted somewhere less then 2 minutes was OK, but it was NOT a linhof back they were testing it with. Also, the ability to measure the film flatness is not easy, as you only have access from the film side. With a good magnifiying system and a micrometer, it is possible though.... this is why most people test with film with flat test target.



> Or you can call us at 800 735-4373 to run a roll through or you can run a film if you are at the show - we would need to know tonight to bring the demo back to the show.

I appreciate the offer, I will not be attending the show....

> This is not a specification the factory publishes but Marflex may have it as a repair spec.

yes, I know, hence why I am probing this forum for answers..... Why do you reccomend Marflex for this? I am not aware of their Linhof association? Just a dealer?

Thanks

[Bob Salomon]

" Why do you reccomend Marflex for this? I am not aware of their Linhof association? "

They have been the only US authorized and factory trained Linhof service center for the past 25 years.