GH2 GH2 testing two c-mount lenses: Computar 12.5 + Schneider 12.5-75

ed_lee83

ed_lee83

Well-known member
The Computar 12.5mm f/1.3 is a great lens to use because it shows very little vignetting. I don't need to use ETC mode. Though it also makes a decent medium lens with ETC (32mm?).
The Schneider 12.5-75mm f/1.8 is a really sharp lens, better quality than other 12.5-75 variants. It's followed closely by the Fujinon f/1.2. Definitely need to use in ETC mode.
I needed to modify both lenses for proper focusing on the GH2.

All the wide shots here are with the Computar, tele shots with the Schneider:

 
Thanks for sharing your video; I enjoyed the festivities. What aperture did you use? The shots don't seem to show much depth of field as I expeced with such fast lenses.
 
Actually i think about 90% of the shots were with the 12.5, so not much DOF there anyway. Thanks for watching.
Personally i'm a bit bored of deliberate shallow DOF, so common nowadays. Super wide and 2.40 anamorphic are my tastes right now!
 
Yes it does. I have noticed that with some zoom lenses that at its most tele mode, the brightness would dim a bit. Is that your concern?
 
Yes, that´s the concern. I bought a cosmicar 1.2/12,5-75mm. It noticeable darkens at least one f-stop at 75mm. So I am looking for a lens not doing so. Do you know, if the canon or Fujinon or cosmicar/ pentax 1.8/ 12,5-75mm keep the f-stop by zooming, too? Thanks
 
I can say the Fujinon f/1.2 dims a bit too. Haven't tried the other versions.
Still, 75mm at that low aperture is fairly good!
 
I have all the proper machines & hardware to do it. Modifying lenses are somewhat a hobby in Hong Kong. Usually it's a case of filing down or extending the rear mount to the optimum position, i.e. infinity focusing throughout the zoom. I've even had to modify the c-mount adapters too. Same case for primes. You need to take your primes to a proper lens tech. I've seen some disastrous DIY jobs... don't attempt if you don't know what you're doing!
 
ed_lee83 said:
Usually it's a case of filing down or extending the rear mount to the optimum position, i.e. infinity focusing throughout the zoom. I've even had to modify the c-mount adapters too. Same case for primes.
Click to expand...
Thanks. I have tried all of my c-mount primes and they all have the same problem. (Schneiders, Switars, Cookes, Berthiot). So, before I take the lenses, adapter & camera to my lens tech, I'd like to know whether others have had my problem. If so, the solution will be widely known. If, on the other hand, my setup is the only one to experience problems, I'd have to suspect the adapter.
 
ed_lee83 said:
It's followed closely by the Fujinon f/1.2. Definitely need to use in ETC mode.
I needed to modify both lenses for proper focusing on the GH2.
Click to expand...

Did you adapt a Fujinon TV lens? Ryszard, who makes the Ciecio B4 to m4/3 adapters told me, " Your lens has B4 mount so it will fit into adapter. You don't have
to use 2x extender with GH2. It has a crop mode so no vignetting occurs."

Did you make your own B4-m/3 mount?
 
No, it was a c-mount.
Never tried those types of lenses before.
Any 'screw' type lens are easier to modify
 
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