Which CCTV lens for wide angle fisheye use ?

TruHype

Hello everyone,

I've recently started to get interested in C mount (CCTV) lens, for they are fast, wide, and cheap. So I wondered, is there any CCTV lens that I could use as a Fisheye (and get the same effect as the Panasonic 8mm f3.5, but faster) ? Here's a few lens I've found looking on the internet :

Rainbow 3.5mm 1.6
Tamron 4-12mm 1.2
Pentax 6mm 1.2 (+ wide conversion lens x0.45)

Wanted effect :

The GH2 exact m4/3 sensor crop is x1.86.

So I would like to get the same widness as the Panasonic 8mm or any 8mm Fisheye (Samyang, Peleng, Rokinon...) :

Panasonic 8mm : 8 x 1.86 = 14.88mm equivalent (no need for ETC mode)

Rainbow 3.5mm : 3.5 x 1.86 = 6.51 -> 6.51 x 2 = 13mm equivalent

Pentax 6mm : 6 x 1.86 = 11.16 -> 11.6 x 2 = 23.2mm equivalent -> 23.2 x 0.45 = 10.44mm equivalent

x 1.86 : GH2 Sensor Crop

x 2 : ETC tele conversion mode crop (to cover vignetting)

x 0.45 : Wide convversion lens

Does that mean we could use any CCTV c mount lens instead of the Panasonic lens to get the wide fisheye effect ?

A few videos :

Lenses :

C mount lens (1/2") work well on the GH2, but I heard that the CS mount lens (1/3") would still have really heavy vignetting because even with the ETC mode it would not cover entirely the GH2 sensor. Is that true ?

Interesting CS mount lens, but 1/3 inch : http://www.ebay.fr/itm/TAMRON-Manual-Iris-CCTV-Lens-3-0-8mm-1-1-0-ASPHERICAL-C-Mount-3-Mega-Pixel-/261248954560?pt=UK_CCTV&hash=item3cd3a6b0c0

I would use the fisheye to film Skateboarding.

Thank you.

nomad

Forget it. The cropping necessary to get rid of vignetting (or even port hole effect) will ruin all your wide angle gained. Even wide lenses made for 1" sensors will vignette on MFT.

Please check the lengthy threads about C-mount lenses.

IronFilm

The problem is C mount lenses are designed to cover a much smaller sensor than m4/3 (there are various sizes C mount lenses are for, your best luck is with a 1" one).

This means for longer lenses (say 25mm and longer) you are sometimes pretty good and get lucky in it covering the whole sensor in your m4/3 camera. But the wider it gets the less likely that is.

My cheapie Fujinon 25mm f/1.4 one only about 99% (or less) covers the sensor of my GH1, but is good enough for me.

The Honeywell 6-12 mm f/1.4 which I own only covers maybe the middle half (or less, a third? Haven't measured exactly) of my sensor, there is a LOT of resulting black edges in my videos!

What I've done is I've ordered a 2x extender (this one: http://www.ebay.com.au/itm/Cosmicar-X2-TV-Extender-80001-2-EX-Lens-/230608452068 , but you can find cheaper) and with any luck this will then make the sensor coverage be wider enough to be more useable. This will mean I then have a 12-24mm lens, but a f/2.8 as I'll loose 2 stops of light. Still, if this works out it should be a pretty ok fun setup for the price! Fingers crossed.

The world of using C mount lenses is a weird and fun one, come deep down the rabbit hole and join us ;-)

IronFilm

Personally if I wanted a useable very wide lens I would go with the Rokinon 8mm Nikon AE (so I can use it on my Nikon DSLR too, as well as my m4/3 cameras), is the simplest and easiest way to go about it (is quite reasonably priced too, I'll likely get it in the near future. Is the lens which is meant to clean up best in post too if you're trying to fix the fisheye effect).

These C mount lenses are more like just cheap fun experiments for me, and is partially about enjoying the hunt, discovery of random gems, and the process of getting them working again :-D

balazer

Search for C-mount fish eye, and you'll find several examples. Fujinon makes some. 3 mm for 1080 ETC mode gives the same angle of view as 8 mm for the full four thirds.

A lens that covers the half inch format just about covers 1080 ETC mode. A lens that covers the one third inch format more than covers 720 ETC mode. There are very few C-mount lenses designed for the four thirds inch format. A one inch format lens would need cropping.

Fish eye lenses in C-mount are not so common. You are probably better off with a photographic fish eye lens.

Manicd

I know this is old thread but I just found out there has been available for over a few months a chinese cctv apc-s sized c mount 8mm 3.8 lens. It covers all of m43 sensor. Sale prices are between $65-85 usd, depending on where you buy it. Is there a thread or list on the internet for cheap lenses that cover the full m43 sensor size?

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