A24 (220 format) is just a double roll length of A12 (120 format). Both gives you 6cm x 6cm image size. Thus there is no difference. The only major concern is the availability of film. Normally 120 rolls are more easy to find in shops, and cheap.
>i've heard that the actual plastic of the film in A12 and A24 is different. > since the A24 has to fit in the same space, the thickness of the plastic >is thinner, thus inferior quality. is this true?
Patrick,220 film is not half the thickness of 120.
i.e. the film and the backing paper of 120 is not a 50%-50% arrangement. When you have dedicated backs or 120/220 pressure plates, you cannot/must not use the wrong film in the wrong back. Your depth of focus is all wrong as the film is not being held in the correct plane, In addition, you'll only get 12 exposures on 220 in a A12 back.
I assumed this was your question. Apologies if I've misunderstood.
May i offer another consideration (a real one, as opposed to this "thickness matters" nonsense ;-))?
220 film is very hard to find, not available in many emulsions, and if rollfilm is on it's way out, after 70 mm, it will be the first to go.
Flatness... well... has it ever been an issue? Have we ever heard people praise the supposed better flatness of 220 film before (!!!) Zeiss wanted to push their Contax vacuum back, which of course only works using 220 film (!!!!!!)?
I know i haven't.
Why is that, i wonder...
Film flatness is very important for certain applications. They are mostly scientific, not artistic, though one straddles both. Photogrammetry and astrometry are ex&les of some of the scientific cases. A vacuum back is useful in long exposure photography (astrophotography) in humid conditions. As the film base absorbs moisture, it tends to curl. The vacuum back delays/prevents this. There are some astrophotographers that modify their backs/cameras with a "dry purge", for ex&le, pumping the back/camera full of nitrogen to displace the humid air.
For most applications film flatness is not an issue. But it does make good marketing copy for those who have money burning a hole in their pockets. Or those trying to make images of subjects a few microns in size on the film plane...
I would offer another "real" suggestion and that is one of number of exposures;i.e. convenience. Many rollfilm users come from or use 35mm.(36exp.typically). I use 220 almost exclusively and yes, I have a vacuum back! I agree 220 is not available at your corner drugstore but then neither is 120. I use Velvia (50/100); Provia (100);Reala; NPC;NPS (160/400); Portra 160 NC/VC and have never experienced any more difficulty in obtaining these than the same emulsions in 120. When shooting weddings or other aasignments, having 32 vs 16 exposures is a real advantage.Another attraction is cost..220 is less than twice 120 and development(film) is only 50% more. So rolls of 220 purchased and processed, can ad up to significant savings on a "job"
ps With the exeption of Kodak Tech.Pan(special use)I have not found any emulsions I use, that cannot be purchased in 220. Where are you??
I have experienced a "severe" problem with film flatness, resulting in = the impossibility to focus the whole picture at once when printing. It was either the center or the sides. The picture was simply lost. This happened with a Lubitel (Soviet all-plastic-cheap MF camera)and I = am keen on beleiving the worse Hasselblad back/film combination is far = better in that respect than the worse Lubitel. So beyond reasonable limits, film flatness can become a real issue.
I know about the importance of film flatness.
I also know how people are easily led by marketing people and their garb.
The "120 vs 220 film flatness"-discussion never ever appeared, until Zeiss's marketing department published their findings.
I'm not disputing any of their findings (we would need to know more details about their test procedure, and how to interpret their results tha we can possibly know), just pointing out that it (flatness) apperently never was a problem for us, "mere photographers" before, yet now (i.e. post-Zeiss) we appear to be very worried.
A nicer ex&le of being led, like simpletons, by what marketing people tell us, instead of trusting our many decades of practical experience you will not find. Don't you think? ;-)
I'm smack in the middle of the civilised world (where i *can* get 120 film). 220 film is not used much (hence the lesser choice in emulsions anywhere in the world), and only available through mail order.
Now if you are in some remote part of the world where nothing is available unless it is flown in, and if you confine your choice of film to those emulsions that are available in 220 film... yes, *then* i can understand you don't see a problem.
We must be neighbours!! I too am in the middle of civilization. I just go to my professional camera store(s)or my lab. to buy the films over the counter. They actually keep them in the fridge!) Things must be different in Europe for you.
having shot the majority of my colour work with an A24 back and quite often swapped to an A12 back loaded with B&W, without changing focus or anything else, I am yet to see any loss in sharpness from the 120 film loaded in the A24 back. I am pretty convinced that the film plane is in the same location for both backs.
Well, Colin, only partly (things being different).
I can stroll over to either of my two close by local photo stores (one very small, the other approaching what one could call almost a fair size small town shop) and buy 120 film over the counter. From the fridge too.
But 220 film?
I'd even have trouble finding that in the somewhat further away large city pro-shop.
Not impossible to get, though.
Seeing what's happening in film-land today (What will the new "Agfa" do? Where will be Ilford be tomorrow? What is Kodak planning next? And how will Fuji see the future?), i would think twice about buying a 220 film A24 back.
Now if only Hasselblad made them so that one back could take both types of film...
You're right. The film plane is indeed in the same spot, the shells and inserts of the Hasselblad 24 and 12 backs being exactly the same.
It's only the wind mechanism that is a bit different.
Zeiss say in effect that 220 film is more flexible, has less tendency to keep the bent shape it acquires when it goes over rollers inside the film magazine, and thus is flatter when in the film gate.
They also recommend not to keep film curved around rollers for more than a few minutes. I guess they are oblivious of the reason both 120 and 220 film are called "roll" film...
So while they worry about film curving around rollers in the back, they forget that film comes tightly wound around spools. Curved. And kept that way before use for a time much, much longer than a ew minutes.
I suggest that we all forget about the first thing too.