Neat little C-Mount lens for M4/3

[Tom Caldwell]

Meopta 80/2.8 - no vignette

• Panasonic - DC-GX9
• 35.0 mm
• ƒ/4
• 1/80 sec
• Pattern
• Auto exposure
• ISO 1600

 

[Yar1971]

Very nice lens. I have Meopta 40/1.8 of similar built. Very solid piece of glass&metal.They both are from 16mm film camera, as far as I remember. I used mine occasionally, thought to use it for night sky photos, but it does have some vignetting wide open. Note: by this I mean absolutely NO dark corners, just some normal (but significant anyway) vignetting frequent in many lenses. For daylight photography absolutely meaningless, IQ is good.
As with longer FL adapted C-mount lenses have commonly more less vignetting problems, I guess Your 80/2.8 is really excellent.
Regards
-J.

 

[Tom Caldwell]

I have the 40mm as well and it does vignette as noted - the 80/2.8 does not and is therefore a handy compact MF lens on a M4/3 camera body.

 

[Tedolph]

Quick question: is there any crop factor when using "C" mount lenses?

I gave up all my full frame adapted lenses when I moved recently and am thinking about a fast 80mm equivalent lens for portraits.

Thanks in advance.

Tedolph

 

[Tom Caldwell]

The unusual thing about putting C-mount lenses on the M4/3 mount is that it is a bit of a lottery on whether you get vignetting and if so just how bad it is. I tried a few C-Mount lenses on mine and was more often disappointed than happy so I gave up trying. But this 80/2.8 is very compact and did not vignette - I had bought it before I gave up on C-Mount as a waste of money - their (Meopta) 40/1.8 lens is another nice looking (and faster) lens but sadly it does vignette more than my taste will allow. But see post by Yar1971 above.

Some C-Mount lenses are too wide bodied to even fit inside the recess necessary in a C-M4/3 adapter.

If the lens doesn't vignette then it is worth a try in my own opinion. The actual crop factor is exactly the same as any other lens and the 80mm f2.8 is equivalent fov to a 160/2.8 on a camera body with a FF sensor. But if a really fast useful lens of high image quality is a concern then the Olympus oem 75/1.8 for M4/3 is another alternative.

However the M4/3 twins Olympus 45/1.8 and Panasonic 42.5/1.7 will give quite acceptably fast oem lenses with portrait-length focal lengths on M4/3 bodies and they are both quite compact.

 

[Tedolph]

Man, that GM-5 is gorgeous......

Tedolph

 

[Yar1971]

The unusual thing about putting C-mount lenses on the M4/3 mount is that it is a bit of a lottery on whether you get vignetting and if so just how bad it is. I tried a few C-Mount lenses on mine and was more often disappointed than happy so I gave up trying. But this 80/2.8 is very compact and did not vignette - I had bought it before I gave up on C-Mount as a waste of money - their (Meopta) 40/1.8 lens is another nice looking (and faster) lens but sadly it does vignette more than my taste will allow. But see post by Yar1971 above.

Some C-Mount lenses are too wide bodied to even fit inside the recess necessary in a C-M4/3 adapter.

If the lens doesn't vignette then it is worth a try in my own opinion. The actual crop factor is exactly the same as any other lens and the 80mm f2.8 is equivalent fov to a 160/2.8 on a camera body with a FF sensor. But if a really fast useful lens of high image quality is a concern then the Olympus oem 75/1.8 for M4/3 is another alternative.

[...]

Yep!
But there'are some rules of thumb here (C-mount on m4/3):
-the more FL the less vignetting
-usually acceptable FL range starts from 25 mm +; everything down 25mm will give You circular sub-frame image on standard m4/3 frame (exceptions are subframe sensors/sensor modes like Black Magic Pocket Camera or some Panasonic crop video modes)
-25 mm is on the edge, depending on the size of the sensor they were originally desinged; in most cases some black vignetting in the very corners, but there are some old TV/film lenses of this FL that can cover the whole m4/3 frame.
Regards,
-J.

 

[Patrick Donnelly]

Yep!
But there'are some rules of thumb here (C-mount on m4/3):
-the more FL the less vignetting
-usually acceptable FL range starts from 25 mm +; everything down 25mm will give You circular sub-frame image on standard m4/3 frame (exceptions are subframe sensors/sensor modes like Black Magic Pocket Camera or some Panasonic crop video modes)
-25 mm is on the edge, depending on the size of the sensor they were originally desinged; in most cases some black vignetting in the very corners, but there are some old TV/film lenses of this FL that can cover the whole m4/3 frame.
Regards,
-J.

Modern c mounts can go much wider as with the Kowa HC series 4.7mm and it fully covers a 1 inch sensor. The 6mm version fully covers some m4/3 sensors, as their 'crop factor' is 2.2x or slightly more. There are videos demonstrating this on my ebay adverts for the 6mm. Massive depth of field! The older cine lenses are for 16mm film and only guaranteed to cover a 2/3 inch sensor like the 4k mode of an EOS M.

Some 12.5mm Cosmicars will fully cover m4/3 2x crop, but only if the filter ring can be removed. Some versions do not allow this and seem to be newer and less generous in coverage.