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Problems with Wide Lenses - Summary

zcream

New member
I spent the past few days researching Fast Wide Angle Primes for the m4/3 cameras. I will use this thread as a summary.
C-mount lenses are available for upto a 1-inch sensor and vignetted heavily at lengths less than 25mm.
35mm fisheyes like Peleng and Samyang 8mm/f3.5 allow a 16mm field of view but need lots of light (it becomes a 16mm f7.0).
So I looked at some other options. An obvious check is to find lenses for sensors greater than 1-inch.
It turns out that the Kodak Kai-4021 sensor is 1.2-inch. Its close enough to the 1.33" m4/3 sensor.
Kodak Kai 4021 based cameras are popular in astronomy applications.
Here are some pics of this sensor with unidentified lenses..
http://www.optcorp.com/cart/productimages/ascent_camera07-L.jpg
http://www.alliedvisiontec.com/uploads/pics/pike-F-421-banner.jpg

I simple search for Kai 4021 lens on google.

So now perhaps we could have a group effort in identifying lenses for such cameras.
 

zcream

New member
Vivek. You are an encyclopedia. That document basically tells me its impossible as all the lenses that work are SLR lenses. I did not recognize the lens on the pic - but I trust your judgement.
For the 8mm f3.5 comparison, the 8mm FOV doubles to 16mm due to the sensor size. Since the image circle now covers half the area, we are collecting less light, so its the equivalent of a 16mm f7 lens on the m4.3 sensor.
Does this not make sense ?
 

photoSmart42

New member
Since the image circle now covers half the area, we are collecting less light, so its the equivalent of a 16mm f7 lens on the m4.3 sensor.
Does this not make sense ?
No, it doesn't make sense. You're collecting the same amount of light per unit area, so f/3.5 is f/3.5 regardless of the sensor size. Your DOF changes because of the sensor size, but the lens allows the same amount of light through. The sensor only sees the middle portion (1/4 area) of the equivalent 35mm/FF lens image.
 
V

Vivek

Guest
No change to the focal length or the aperture due to the format.

I would wait for the 14/2.5 and the 8/3.5 fisheye from Pana for the m4/3rds.

I say this after having experimented with quite few combinations ( 25/1.9 Xenoplan plus a 0.5 reducer, 17/2.8 Oly-D plus Ricoh 0.75X converter, 25/1.3 Computar-TV plus a 0.65X Century Optics converter, Fujinon-TV 12.5mm f/1.4 lens, tinkered 12.5mm Fujinon-TV lens, ..etc).
 

zcream

New member
Has anyone tried this lens
Fujinon FE185C086HA-1 1" C Mount 2.7mm F1.8 5 Megapixel Manual Iris Fisheye Lens

I know 1-inch is smaller than needed but still worth checking.
 
V

Vivek

Guest
Has anyone tried this lens
Fujinon FE185C086HA-1 1" C Mount 2.7mm F1.8 5 Megapixel Manual Iris Fisheye Lens

I know 1-inch is smaller than needed but still worth checking.

I agree. I would love to try it if someone would donate a sample.;)
 

zcream

New member
With further research, here are the currently available "popular" Manual IRIS, Fixed Focal Cmount lenses on BH.
http://www.bhphotovideo.com/c/search?ci=3659&N=4293342916+4291756351+4289303209+4289302490
Just 12 in total. Here are the wides .
Fujinon
CF125HA-1 1" 12.5mm Industrial Lens
Fujinon
FE185C086HA-1 1" C Mount 2.7mm
Fujinon
CF16HA-1 16 mm f/1.4 Industrial Lens, Manual Iris
Pentax
C20616TH 6.5 mm f/1.8 Fixed Focus Industrial Lens
Pentax
12.5mm f/1.8 C-MT MANUAL IRIS - 1"


Perhaps we could start by seeing what lenses have been used and known NOT to work,
 

zcream

New member
Paparazzi66 posted these lenses as his recs.
The Cosmicar and Pentax are the same.
I remember a review of the 12.5mm f1.4 and it crops a fair bit.
I have yet to see reviews of the other lenses.
- 4.5mm f2 tamron
- 6.5mm f1.8 cosmicar
- 12.5mm f1.4 cosmicar
 

zcream

New member
From the Google spreadsheet
http://spreadsheets.google.com/pub?key=p9kkgjwEQQQ-HJwvNDobeEw
Cosmicar 12.5 1.4 Yes no wjlapier, monza

Tested and it vignettes. Here are some samples.
http://forums.dpreview.com/forums/read.asp?forum=1038&message=32224856

Description of the mod, but I still missed a fullframe pic showing the vignetting.
http://forum.getdpi.com/forum/showthread.php?p=188414

However, Godfrey has not given an uncropped pic to check the extent of vignetting. Other users are
monza
http://forum.getdpi.com/forum/showthread.php?t=6941

Though he did not post a full frame from the 12.5mm f1.4
 

zcream

New member
Now we still need a full frame pic the 12.5mm f1.4 and there are still 4 more options to go.
Ideally if someone works or knows someone in a CCTV dealership, they could have access to these lenses. No need for an adapter, just hold it in front of the camera, point at white paper and theres an approx idea of the coverage.
 

zcream

New member
So is this statement correct,
I get a doubling of the FOV due to the smaller sensor and a doubling of the equivalent DOF. So its a f7 equivalent DOF.

No, it doesn't make sense. You're collecting the same amount of light per unit area, so f/3.5 is f/3.5 regardless of the sensor size. Your DOF changes because of the sensor size, but the lens allows the same amount of light through. The sensor only sees the middle portion (1/4 area) of the equivalent 35mm/FF lens image.
 

photoSmart42

New member
So is this statement correct,
I get a doubling of the FOV due to the smaller sensor and a doubling of the equivalent DOF. So its a f7 equivalent DOF.
Correct. Equivalent FOV and DOF change due to sensor size, the amount of light per unit area is the same for a given lens at a given aperture setting.
 
M

mjohnston

Guest
Just naturally dark. That's one of the best ways to use this kind of lens; work within the limitation, or purposefully use the parascope effect :)
 

zcream

New member
Has anyone experimented with 6.5mm lenses ? There are a few different ones - from f1.4 to f1.8 available on 2/3 and 1-inch sensors. I just bought a Computar 12.5m f1.3 lens from ebay.
 
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