C-mount lenses on the EOS-M

[Janke]

Thanks, a1ex, that was an interesting little video. Loved the math formula, it looked kinda cool!

I had my chances

They still abound on eBay.

[Oswald]

Here's my little test using 8-48mm f1.0  (it is fast) with 3x crop mode. Eos M is little beast! 

Iso 400 and shutter 1/50 almost all shot in f1.0

[AnthonyEngelken]

I too, put on the Fujian onto my EOS-M on a lark and now I can't bear to take it off!

Received my Fujian today, and I have a couple of questions for you. Seems the back focus needs a little adjustment to have accurate infinity, same case with yours? If I unscrew the lens a ways, I'm able to correct this, and I'm just wanting to make sure my adapter is built right. Also, I don't know what the GH1/NEX guys are talking about, but I have zero vignetting with this glass; seems to cover the whole sensor. Again, same case with you?

[Janke]

Haven't got mine yet.

But, don't fret about that infinity focus - there's quite a bit of tolerance in cheap CCTV lenses.

If you get infinity by unscrewing the lens, it means you will be able to shim it slightly, i.e a little ring of some suitable material between the lens and the adapter takes care of it.

OTOH, you will get infinity without any shim, but the scale on the lens will be off a bit. Happens with most CCTV lenses. You do focus via the finder, right? It may even be possible to correct the error, if the focus ring is movable - are there some very small screws along the rim? But don't mess with them if you're not sure what you're doing...

Much worse is not getting to infinity at all, then some lathe or mill work is needed to seat the lens further inwards.

[AnthonyEngelken]

If you get infinity by unscrewing the lens, it means you will be able to shim it slightly, i.e a little ring of some suitable material between the lens and the adapter takes care of it.

Good to know this isn't out of the ordinary, will probably hit up the hardware store tomorrow for some washers.

[Janke]

Remember that the C-mount has a 1/32" (almost exactly 0.8 mm) pitch; you can easily calculate the thickness of the shim from that, checking how many degrees you have to unscrew the lens to get infinity focus when the focus ring is on infinity...

I had to add a very thin shim to my 12.5-75mm zoom to get it to keep focus over the zoom range.

Focusing at telephoto, and zooming to wide, the focus shifted from infinity to 3 meters, and calculating with the lens formula 1/a + 1/b = 1/f  thus 1/x + 1/3000 = 1/12.5 gave me ∆f = 0.052 mm - so, two layers of scotch tape between lens and adapter was enough!

[AnthonyEngelken]

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[maxotics]

Received my Fujian today, and I have a couple of questions for you. Seems the back focus needs a little adjustment to have accurate infinity, same case with yours? If I unscrew the lens a ways, I'm able to correct this, and I'm just wanting to make sure my adapter is built right. Also, I don't know what the GH1/NEX guys are talking about, but I have zero vignetting with this glass; seems to cover the whole sensor. Again, same case with you?

I never use the lens to take a photo of anything at infinity   For me it's a shallow-depth of field bokeh monster.  I know you can calibrate it to focus properly at infinity, as the other posters say, but I never bothered. 

The benefit of this lens, to me, is it takes you away from the technology and back to primitive imaging--though with fantastic sharpness in the center (or where you're focused.). 

[AnthonyEngelken]

The benefit of this lens, to me, is it takes you away from the technology and back to primitive imaging--though with fantastic sharpness in the center (or where you're focused.).

Totally agree with this, but calibration never hurt anyone. Love the lens, by the way; beautiful shots so far.

[Janke]

Love the lens, by the way; beautiful shots so far.

Can't wait till I get mine... it was shipped 4 days ago...

[tupp]

Got my EOS-M with the Fujian 35mm f1.7!

The lens (and camera) is fantastic and fun, and it is amazing that it does not vignette on the ASP-C sensor (the lens is rated for a 2/3" sensor).

However, I am noticing an excessive "circular of flare" in the center of the frame, on the widest f-stops.  I know it is flare, because I can flag it with my hand.  This flare is so excessive, that, if a little bit of light hits my hand, the color of the "circle of flare" (on the side closest to my hand) changes to the color of my hand.

Anyone else notice the same phenomenon?

I think that the filter size of my Fujian is 35mm wide, so I will probably try a long lens hood.

[dfort]

The Fujian 35mm f1.7 lens is gaining quite a following. There's even a Flickr group for that lens: http://www.flickr.com/groups/2062341@N22/

I got the fever and ordered an EOS-M and the Fujian lens. One thing I'd like to do is to play around with the 3x zoom with 1280x720 raw video. I did some quick calculations and the 22.3 wide APS-C sensor in 3x crop comes out to 7.4mm which is between somewhere 2/3 inch and 1/2 inch video.

Of course there's lots of C-mount lenses out there but watch out--many of the shorter focal length lenses are for 1/2 inch or even 1/3 inch sensors. I looked up some film/video formats and here's what I found:

Format              Width
1 inch video     12.8mm
Super 16mm    12.5mm
Reg. 16mm      10.26mm
2/3 inch video    8.8mm
1/2 inch video    6.4mm
Super 8mm        5.79mm
1/3 inch video    4.8mm

As long as I'm throwing out a bunch of numbers, the EOS-M sensor is listed at 5,184 pixels wide. At 16:9 it should be using 2,916 vertical pixels. Scaling this down to 1280x720 to avoid "line skipping" I came up with a 4.05 crop factor so that means that there still must be some scaling/line skipping going on in 3x crop. However, the videos I've seen done at 3x and 1280x720 on Canon APS-C sensor cameras don't exhibit any aliasing or moire pattern issues. Can anyone explain why? (1% answered this question.)

(Note: I edited this post on March 3, 2014. I originally had the width and height of Super16mm transposed and was under the impression that the 3x crop mode on the EOS-M would turn it into a Super16mm camera--I was wrong.)

References:
http://www.lensrentals.com/blog/2012/01/sensor-size-matters-part-1
http://en.wikipedia.org/wiki/Image_sensor_format

[dfort]

1% elaborated on line skipping in 3x crop mode in another post: http://www.magiclantern.fm/forum/index.php?topic=10056.msg103983#msg103983

Back to C mount lenses. I had a little CCTV camera that used CS mount lenses. C mount lenses could be adapted to CS mount cameras but not the other way around. The threads are identical but there's a 5mm flange to focal plane difference. If your "C mount" lens doesn't focus to infinity it is probably a CS mount lens.

[AnthonyEngelken]

The lens (and camera) is fantastic and fun, and it is amazing that it does not vignette on the ASP-C sensor (the lens is rated for a 2/3" sensor).

Fujian was probably taking into account the barrel distortion while making the 2/3" claim.

Was under the impression that the 3x crop mode on the EOS-M would turn it into a Super16mm camera--I was wrong.

Not necessarily; in movie crop mode, Super 16 glass would be quite ideal for 2k raw sensor utilization (if the M could capture more than a second or two of 2k raw). Standard 16 glass on the other hand projects about the perfect circle for 1080p h264 capture in 2.7x crop mode. The M's sensor/pixel proportions don't seem terribly different from the Digital Bolex's.

I have a question for those in the know: Is it just me, or is the field of view much narrower on a c-mount 35mm than on an ef-mount 35mm? Rather, I was expecting my c-mount 35mm to have a similar field of view in crop mode as an ef-mount 35mm in full-sensor mode, but that doesn't seem to be the case. Instead, both the c-mount and the ef-mount lenses have about the same field of view in crop mode.

Maybe I need a cinema history lesson, but were much wider lenses used back in the day when 16mm was common? In effect, while 25mm is sort of a go-to wide for Super35 format today, did the go-to wide use to be 8mm or 12mm for Super16 format?

[dfort]

Is it just me, or is the field of view much narrower on a c-mount 35mm than on an ef-mount 35mm? Rather, I was expecting my c-mount 35mm to have a similar field of view in crop mode as an ef-mount 35mm in full-sensor mode, but that doesn't seem to be the case. Instead, both the c-mount and the ef-mount lenses have about the same field of view in crop mode.

Huh? Both the 35mm C-mount and the 35mm EF-mount lenses should have the same field of view. There are some variable that will might the field of view slightly different but they should be fairly close.

Remembering way back when I first picked up a 16mm camera the "normal" lens was a 25mm. For a 35mm "Academy Aperture" movie camera it was 50mm and for a 35mm full frame still camera it was also 50mm. On the EOS-M in crop mode I tried a 12mm lens and it seems a bit too long for me so I ordered an 8.5mm lens.

Here's a Wikipedia page that does a fairly good job at explaining how to determine a "normal" lens for still and motion picture film and digital formats: http://en.wikipedia.org/wiki/Normal_lens

I've never very "normal" in my choice of lenses or anything else for that matter.

I'm discovering that it is a challenge to find decent C-mount lenses wide enough make shooting with the EOS-M in 3x crop mode practical. If you have experimented with raw video on the EOS-M you'll discover that 1280x720, 3x crop, RAW and not MLV RAW (which means no audio), Global Draw off, and a few other tweaks are needed to get the camera to record more than a few seconds of raw video. Then there's the whole post production process that I won't get into on a post about lenses!

[AnthonyEngelken]

Captured some footage with a Computar 12.5-75mm f/1.2, shared to the forum here: http://magiclantern.fm/forum/index.php?topic=11456.0

[canoneer]

Just got a Fujian 35/1.7 from Hong Kong with EOs M adapter. But focus is only within a very limited distance and not anything further than 4-5 feet/ 1 ++ meter. I understand that should indicate a to large distance from lense to chip. But how....?

[tweak]

I think that means you need to shave some metal off your lens or adapter (or both). What adapter do you use?

What adapters is everyone here using?

[AnthonyEngelken]

Just got a Fujian 35/1.7 from Hong Kong with EOs M adapter. But focus is only within a very limited distance and not anything further than 4-5 feet/ 1 ++ meter. I understand that should indicate a to large distance from lense to chip. But how....?

Don't shave anything off the lens, the Fujian 35 needs a shim for most adapters (I discovered); a 1/16" rubber ring from your neighborhood hardware store should do the trick. You'll always be fiddling with tightening and loosening the threads to get proper infinity focus, but that's CCTV lenses for ya'. If this doesn't help and the flange distance is in fact too long, return your adapter and get a different one.

[LeicaFan]

I too, put on the Fujian onto my EOS-M on a lark and now I can't bear to take it off!

I can see why you like that Fujian C Lens

The dramatic difference between in focus & out of focus areas really makes for nice looking video.

[canoneer]

I returned the lens and got a replacement quickly - which work great.

[tweak]

I just modded the Fujinon 1.4/9mm C-mount to fit my EOS-M... what  lens! I used a Fotga adapter and had to dremel both lens and adapter to get a flush fit, now it focuses to infinity.

[QuickHitRecord]

Reviving an old thread. I recently came into a few C-mount lenses that I would like to try out, but I've been out of the ML loop for a bit. What is the state of EOS-M crop-mode shooting in 2019? Am I right in understanding that there are now two modes that allow pixel to pixel cropped recording? If so, what are the advantages of each? Thanks.

[dfort]

Am I right in understanding that there are now two modes that allow pixel to pixel cropped recording? If so, what are the advantages of each?

Not sure what you are understanding. There are a bunch of new resolutions available in the crop_rec module if you download Danne's bleeding edge builds. I'd suggest reading up on the latest developments on the Canon EOS M topic. Note that even though these new resolutions are in the crop_rec module some of them use the entire sensor area so if you are planning on using C-mount lenses check to see if your lens can cover the whole APS-C area.