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[OM] Re: Resolution of MF enlarger lenses,

Subject: [OM] Re: Resolution of MF enlarger lenses,
From: Tim Hughes <timhughes@xxxxxxxx>
Date: Tue, 22 May 2007 16:48:51 -0700 (PDT)
I dont know about the greater than 150mm lenses, but the shorter lenses have 
common flange sizes
so it is not a big chore to adapt using an enlarger lens board say and the 
normal enlarger lens
retainging ring.  An/Or make one from a T mount.

The easiest is just to make sure to buy the enlarger lens already with a 
standard 39mm enlarger
screw mount (same as leica screw), which you can easily get adapters for.  I 
have a couple of
novoflex (with OM mount) bellows, but with 39mm screw flanges mounted on the 
front. 

You can buy a 39mm enlarger flange mount for $5 or so from a darkroom supply 
and mount it on any
Tmount (or bellows) by drilling 3 screw holes or even glue it on, if totally 
averse to using
tools. 

Novoflex sells all sorts of flanges and adapters for their bellows but 
unfortunately at a price!  
SG Grimes used to also. 

I believe somebody mentioned you can get Tmounts for E-series but I don't have 
experience.
Obviously Emount-OM-OM-Tmount-39mm would be very clunky!

Tim Hughes

> 
> 1. Bellows. These lenses don't have any focusing mechanism, so they need 
> to be bellows mounted. A normal 35mm style bellows won't work with the 
> long ones. The rear portion of a Schneider Componon 150/5.6 fits into an 
> OM mount on the bellows with about enough room to spare to allow an 
> adapter. A 240/5.6 and a Rodenstock Omegaron 210/4.5 are both WAY too 
> big to fit. At least a MF bellows would be required.
> 
> 2. Mounting. No problem for someone with access to a machine shop.  :-) 
>   I don't know if the mounting threads for these lenses have some sort 
> of standards, but if so, they are not related to anything to do with 
> 35mm format equipment. All that I've seen come with a mounting ring to 
> attach them to a lens board using a simple hole of the appropriate size.
> > But then I wondered if any of these long lenses are really up to the 
> > task.  
> Yes, I believe they are. The long fl enlarging lenses I have are left 
> over from production of a series of rather large rear projection units 
> for viewing maps and aerial photos that I conceived of, helped design 
> and had built. They projected 4x5" transparencies onto 6x7 foot screens. 
> Using a rotating turret, and film holder that moved up and down in the 
> optical plane, ala the Beseler "Cone of Light", and orthogonally to the 
> optical axis to allow viewing any part at higher magnifications, all 
> automated, they projected at three different magnifications.
> 
> We used a custom built camera with another 240 mm Componon with shutter 
> to make the slides and used a special order Kodak film originally 
> created for high altitude photography, It was rumored it was developed 
> for the U2s. Whatever its provenance, it was astonishingly sharp and 
> grainless. Just a little tricky to process, which we also did ourselves. 
> A group from the Lawrence Livermore Lab came to visit once to find out 
> from my cartographer/photographer how to process it without the emulsion 
> sloughing off and going down the drain.  :-) 
> 
> Anyway, I don't remember now the maximum magnification, but it was 
> around 40x with a 105 mm lens. I could stand right up at the screen and 
> see no grain and lots of detail. The lowest magnification was still 
> about 17x, and very high quality.
> > It has been rumored that some 35mm Canyon lenses are not up to 
> > the resolution demands required by the pixel density of the 5D and other 
> > full frame digitals.  
> AF general purpose taking lenses and top quality enlarging lenses are 
> almost unrelated. The optical requirements and resulting designs are 
> sooo different.
> > Furthermore, MF lenses don't need to be designed with resolving power 
> > equivalent to 35mm
> lenses
> We've been around this one before, with all sorts of theories propounded 
> and positions taken. The generally likely truth is that the optical 
> tradeoffs to maintain reasonably flat field and minimal aberrations over 
> the bigger image circle do almost certainly mean lower lppmm resolutions 
> in MF lenses, although probably not in proportion to the increased 
> negative size. Still, you are again talking about taking lenses, not 
> enlarging lenses
> > so what's the chance that an MF enlarging lens will resolve 13MP on a 35mm 
> > size frame
> I think it's pretty good, based on my experience..
> > let alone the higher pixel density of smaller sensor cameras?
> >   
> Who cares?  ;-)
> 
> Moose
> 
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