My goal with this test was to focus on whether c-mount zoom lenses in general are worth using with the GH1 for film. There have been a few posts on the net by still photographers but not many tests from filmmakers. Most results have been so so though.This is mainly because c-mount zoom lenses generally have a small image circle and do not fill the image sensor of the GH1. So you get the Peep Hole or looking though the lens of a barrel effect.
So here’s the bad with c-mount zoom lenses:
- Image circle smaller than sensor
- Vignetting and smearing at the edges of the frame
- Resolution loss
- Wide focal lengths have very small image circles, nothing usable until 25mm- 35mm and higher focal lengths
- Depending on the lens, you may need to machine it to fit the c-mount adapter in order to achieve infinity focus
Alright that’s a lot of not so great reasons especially for those like myself who are filmmakers unless you have a stylistic piece you want that image circle to fill that entire sensor through out the zoom range.
So why waste the time.
Because I’m stubborn and I want to make it work anyway. 
So I thought I’d test it out.
The first lens that I’ll be testing is the Angenieux Type L2/L3 1:2.2/17-68 c-mount zoom lens. It is not perfect by any means and has many of the problems that I pointed out that are the downsides with c-mount zooms but over all I was pleasantly surprised to see some really good results. The clip that is posted here are just straight up mundane doc style footage. Nothing fancy. Just cut and dry. So please excuse some of the shakiness and random footage or commentary by me at the end. I didn’t have my tripod and am still testing out my own variation of a Gorillapod and a Noga Arm called a Gorilla Noga.
The footage was shot in my stomping grounds Chinatown North and Chinatown proper in Philadelphia. I used no ND filters just the lens and shot only 1080/24p with a shutter of 50 and 720/30p with a shutter of 50 as well. All clips had pull down removed using compressor.
Obviously,when using the GH1 digital 2x setting, you are getting an image that is cropped with resolution loss but the results are better than expected. I think scaling up the image and cropping out the vignetting and the “Peep Hole Effect” in Final Cut Pro seems to help with a better image but I have to do a few more tests to be sure. I think despite the image resolution loss it would be very usable for HD presentations on your HD Flatscreen tv or local indy community film screening. For those who are still putting out SD material which we all still do, the footage will be very usable.
Here are a few pluses for using zoom lenses on a GH1:
- You can find c-mount zoom lenses that are faster, many can find at f/2.2, f/1.9 even f/1.2!!
- Many c-mount zoom lenses are smaller and lighter than the stock lens especially tv lenses
- You can focus much more easily with a small c-mount zoom than the stock lens
- Some are still super cheap!! You can find many c-mount zoom security lenses or tv lenses for $50-$100
- Despite the resolution loss you can still use the digital 2x and get some nice results or shoot wide with the peep hole circle showing and enlarge and crop in post and get better results.
- So you lose your wide shots with the digital 2x zoom, just step back farther when you are shooting!