220 Roll film

[alan_higgins]

Hi there

 

Am I right in saying that 220 roll film is just the same as 120 but with 24

exposures

 

Alan

[david_dorcich1]

220 doesn't have the paper backing that 120 does. That is how they fit on the same size reel.

[alan_higgins]

Does that make a difference?

 

Alan

[david_dorcich1]

Requires a different pressure plate setting in the camera in order to keep the film flat, since 220 is thinner without the paper behind the film. That is why 120, and 220 film backs use different inserts. Some tlr's have a switch that moves the pressure plate to allow the use of 220 rolls.

[alan_higgins]

Thankyou for the help David

 

Can you tell me please then is it possible to use 120 in a 220 hasselblad film back or is the 220 specific to the A24?

 

Alan

[david_dorcich1]

You can just be sure to stop after 12th frame. You might loose some sharpness from the difference in film flatness but you can gauge that after a few rolls if you find is acceptable. You won't damage anything by trying.

[q.g._de_bakker]

The length of film that is transported per revolution of tha take up spool is determined by the diameter of the take up spool, i.e. by how much film is already on there, and how thick the film is that is wound on to it to transport enough to put the next frame in the film gate.<br>Since there are no sprocket holes to count, the mechanisms inside cameras and film backs make use of the knowledge about this, turned into cams or gearings that set the always changing number of revolutions the take up spool will make when advancing the film.<br><br>220 film, not having the paper backing the 120 film does, is thinner, and thus requires a different transport/spacing mechanism.<br>So yes, you can put 120 film in a 220 back, but spacing will be terrible. Expect to only get 11 frames on the 120 roll.<br><br>You do not need a different pressure plate (setting). All the pressure plate in Hasselblad magazines does is push the front of the film (220) or film + paper (120) in the correct position. It does that equally well, no matter what film is used.

[alan_higgins]

As always thanks guys

 

This brings me to my next question.

 

If I were to purchase an A24 for 220, how suitable would it be for weddings assuming I have a lab to process and given the fact that it is thinner. If it is not suitable for weddings then what would it be useful for?

 

Alan

[antonio_garcia_russell]

Alan, you can use 120 film in an A24 back as well as 220 film, the only difference is that

you get 1 frame less using 120 film than you would using an a12 back.

 

As regards suitability for weddings I would say it would be very suitable if the emuslions

you use are available in 220, as you would spend less time changing films.

[rodeo_joe1]

"The length of film that is transported per revolution of tha take up spool is determined by the diameter of the take up spool" - I'm afraid you're wrong Q.G. Most decent cameras actually meter the LENGTH of film passing through the gate by a contact friction-roller or serrated wheel on the edge of the film.

 

The frame is measured by a certain number of revolutions of this contact wheel, and since the contact wheel has a fixed diameter, the length of film per frame should be reasonably consistent.

 

It's only pieces of junk like the Kiev60 that space their frames by counting revs of the film spool.

[antonio_garcia_russell]

Joe, you are correct. The take up spool does not determine spacing. Here is what David

Odess had to say about this <A HREF="http://www.photo.net/bboard/q-and-a-fetch-msg?

msg_id=00OcvX"> recently </A>

:

<p><i>

"The amount of film that is actually moved from one exposure to the next is determined

by the film magazine. This is accomplished by a number of arms and gears. Once the

proper amount of film for each exposure has been transported, the drive system in the

film back is disengaged, allowing for the complete cycling of the film magazine without

transporting any more film"</i>

<p>

[q.g._de_bakker]

Joe,<br><br>Also pieces of junk like the Hasselblad magazines space their frames, not by counting the revolutions, but presetting the number of revolutions of the take up spool. ;-)<br><br>Alan,<br><br>There are very few emulsions left that are available in 220 film, Luckily, Kodak's Portra 160 NC is one of them. As long as they keep selling it in this confection size, using 220 film makes sense.

[q.g._de_bakker]

Now do not start spreading misinformation once again.<br>The changing diameter of the spool does indeed determine what length of film is transported during one revolution of it. That's simple physics.<br>So what they do is regulate the number of revolutions it is allowed to make each time film has to be transported to a next frame. The mechanism David mentioned does exactly that. It actually is the 'knowledge turned into hardware'. And it is also the reason why frame spacing is off when you do not load the film properly: if you do not, these presumptions built into the mechanism isn't correct.<br><br>If you do not believe that, mail David, and he'll confirm that it is indeed true.

[russ_britt3]

And it is also the reason why frame spacing is off when you do not load the film properly: if you do not, these presumptions built into the mechanism isn't correct.

 

I guess we could say that all hasselblads space images incorectly now....Russ says while grinning...Q.G.

Ihave heard it said thats its had to make things foolproof, because fools are very persistant!

[antonio_garcia_russell]

Film spacing is determined by arms and gears as described by David Odess. I imagine

Hasselblad would have taken into account the changing diameter of the film spool when

designing the arms and gears, but the diameter plays not direct role, per se, in the

mechanism. i.e. the mechanism will actually operate even when there is no film in the

film magazine. It is therefore incorrect to make out that the changing diameter has a

direct influence on film spacing. It does not, the gears do. Which is why film backs that

have spacing issues require the gear mechanism to be adjusted (as oposed to some non-

existent spool diameter sensor). The entire system is driven by the wind lever, which sets

the shutter, lowers the mirror and winds the film on.

[antonio_garcia_russell]

Actually, the Hasselblad film magazines are pretty basic design. I much prefer the original

Rolleiflex film feeler mechanism that automaticaly detects the beggning of film, without

having to line up against the arrow...

[q.g._de_bakker]

Antonio,<br><br>What do you think these "arms and gears" do, and how? And why exactly that?<br><br>These "arms and gears" kick the transport mechanism out of engagement with the camera's wheel driving it. When they do that is regulated by a spacing gear. The shape of this gear is a reflection of the ever changing amount of film that is wound by each revolution of the take up spool with a certain amount of film wrapped round it.<br>So there indeed is a direct link between the fact that the increasing take up spool diameter determines the length of film that is transported each time it is rotated, and the mechanism that regulates the number of rotations this spool is allowed to make.

[antonio_garcia_russell]

Bakker,

 

I think it would be more honest of you to accept that you got it wrong (not for the first

time) rather than casting aspertions about me.

 

I realise that English is probably not your native language, so I am willing to accept that

you actually meant to say something different from what you actually said - but the

insults and abuse are surplus to requirements in any event. I dont know who determind

you to be the know it all expert on all issues Hasselblad. Certainly my experience of you

has been that you do get things wrong, sometimes because you are in such a hurry to

prove that you have the answer that you clearly have jumped the gun. I suggest you take

time to check you have fully understand what is being said in future before criticising.

[q.g._de_bakker]

Antionio,<br><br>You are susch a tiresome person...<br>So please do amuse us all for a change, and try to point out what was wrong in what i wrote.<br>And when you too finally see that you can't (which you indeed cannot) stop bothering us all with your mis- and desinformation.

[antonio_garcia_russell]

I have reported you to the Moderator Q.G. (for the second time). If you dont agree with me

fine (debate is after all, par for the course on a discussion forum), but there is no need for

the insults.

[antonio_garcia_russell]

Q.G., But the important point you are ignoring is that there is no take up spool diameter

sensing mechanism in Hasselblad film magazines. Whatever calcuations Hasselblad used for

its gear mechanism are actually fixed calcualtions. They do not sense the film being wound

onto the take up spool. And they cannot, for example, tell the difference between newer

(thinner) and older (thicker emulsions), and, apropos the OP, they cannot tell if 120 or 220

film is inserted in the magazine. They just wind on according to a preset regime.

[alan_higgins]

Hi guys

 

I myself would really like to know what the answer is to the A24 back and am grateful for the debate, but please chill out and let each other speak

 

Thanks

 

Alan

[antonio_garcia_russell]

Alan,

 

Basically, as stated above, you can use 120 film in your A24 back but (because it is designed

for 220 film) it will spread the frames out more than with an A12 back, so that you will only

get 11 frames on a roll of 120 film. But otherwise they are perfectly usable and actually

often a cheap way to get a film magazine, given that A24 backs seem to sell for less second

hand.

[q.g._de_bakker]

Antonio,<br><br>There we have it, once again.<br>If you would bother to read what people write, instead of following your own agenda, you would have seen that noone wrote that there is a "take up spool diameter sensing mechanism in Hasselblad film magazines".<br><br>So now write to the moderator again, to promise him that you will stop your nonsense, and will try to contribute to discussions in a sensible and helpful way.

[rodeo_joe1]

OK. I'm attaching a picture I took of a Mamiya insert showing the film metering friction roller (A) and the cog at the other end of its spindle (B) which tells the camera when one frame's worth of film has passed through the gate. I also have a YashicaMat dating back to 1959 which uses a very similar roller, so the idea isn't new.

 

In fact most rollfilm cameras have something similar, be it a friction roller, serrated wheel, or a spindle that the entire film passes over.

 

It's easy to see that this mechanism is entirely independent of the amount of film on the spools, and it's easy to check practically too. If you have an empty rollfilm camera - no film or spools - then the camera will just wind on forever, without ever getting to frame 1. That's because film is needed to turn the measuring spindle and the frame counter.<div></div>