C-mount adapter question
- Thread starter henryciullo
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henryciullo
Active member
Barry_Green
Moderator
Welcome to using c-mount on a GH1. That's what happens when you use a wide-angle lens. The c-mount lenses are only designed to cover the 16mm frame, which is about a 10mm circle. The GH1's sensor is 13mm tall, and 18mm wide -- so yeah, you get a circle of image within a big black void.
Try zooming in past about 35mm and you should get full-frame imaging.
Try zooming in past about 35mm and you should get full-frame imaging.
henryciullo
Active member
i actually did try zooming in and nothing changed... there was no change in 'peephole' if i was in 17 or 70 mm position.. of course i could see the image zoom in, but the black border did not change size....
tomorrow i'll try with a meopta 20mm and 80mm (the only other c mount lenses i have).
The adapter i got was from ebay from seller nikon_discount, don't know if anybody else is using that version.
tomorrow i'll try with a meopta 20mm and 80mm (the only other c mount lenses i have).
The adapter i got was from ebay from seller nikon_discount, don't know if anybody else is using that version.
There's no change because of the adapter. The lens itself will provide more coverage as you get to the longer focal lengths, but the adapter is cutting off the image circle. Unfortunately, it's just the limitation of the C-mount and your adapter and the lenses in combination.
DanDOF
Well-known member
I'd like to see how much vignetting there is when you do a 2x digital zoom in-camera (not in post). Could you post a pic?
Strange thought that at 50mm you'd get vigetting - even past 25mm, let alone 35mm (according to this spreadsheet).
Strange thought that at 50mm you'd get vigetting - even past 25mm, let alone 35mm (according to this spreadsheet).
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Barry_Green
Moderator
2x digital zoom will eliminate most of the vignetting, but will result in a picture that's standard-def or worse.
thisisapocalypse
Well-known member
I can't fully confirm this, but at least with the c-mount zooms that I have, vignetting doesn't go away even at longer focal lengths. It appears that it may only be fixed focal length c-mount lenses longer than about 35mm that don't vignette on the GH1, so far all the footage I've seen from c-mount zooms has been similar, the image circle doesn't change in size when zooming, it's that way on all 3 of my c-mount zooms. 2x digital zoom does eliminate the vignetting, but then, i'm not sure the point (in HD mode) of doing this since there is the big drop in resolution when using 2x digital zoom.
I suppose if you really needed a super-long focal length at a fast aperture, say for instance, then it might be worth the drop in resolution, but I would think these instances would be few in far between. It's a bummer, I've got a Canon 18-108 constant f1.6, but I am just not sure it's worth using in 2x digital zoom mode for video. Figuring in both the crop and digital zoom factor, it would have the FOV of a 432mm lens (on a 35mm film camera) at f1.6...tempting, and cool, but at the expense of very precious resolution...that and I'm not sure what I'd use that for...perhaps owl watching?
I suppose if you really needed a super-long focal length at a fast aperture, say for instance, then it might be worth the drop in resolution, but I would think these instances would be few in far between. It's a bummer, I've got a Canon 18-108 constant f1.6, but I am just not sure it's worth using in 2x digital zoom mode for video. Figuring in both the crop and digital zoom factor, it would have the FOV of a 432mm lens (on a 35mm film camera) at f1.6...tempting, and cool, but at the expense of very precious resolution...that and I'm not sure what I'd use that for...perhaps owl watching?
henryciullo
Active member
this morning tried out other 2 lenses
First is a Meopta 80 mm @ F2.8
Second is Meopta 20mm @F1.8
first time i've evere used these lenses cos they came with an old Admira 16mm cam that i got for 20 euros and never used.... both filmed at ISO100 ... with stock lens had to up to 800 to get decent exposure in the same room.
First is a Meopta 80 mm @ F2.8
Second is Meopta 20mm @F1.8
first time i've evere used these lenses cos they came with an old Admira 16mm cam that i got for 20 euros and never used.... both filmed at ISO100 ... with stock lens had to up to 800 to get decent exposure in the same room.
