Author Topic: C mount lenses 5x crop mode  (Read 13530 times)

visiono

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C mount lenses 5x crop mode
« on: August 07, 2015, 09:28:22 PM »
anyone using this method to get decent sharp images from these normally soft focus lenses at wide open?
what about 8mm computar c mount or the 8-48 f1.0?

dpjpandone

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Re: C mount lenses 5x crop mode
« Reply #1 on: August 14, 2015, 10:17:29 PM »
Yes, i have a rainbow h6x8 (8-48mm f1.0)

I adjusted the backfocus, and it's parfocal (stays in focus throughout zoom range. It has acceptable sharpness from f2.0 and up.

It has a bit of a blue-green color cast, but I usually use colorpicker to set WB in post and I'm quite happy with the results. I should mention that I'm using this with eos-m and the small flange to sensor depth is what makes it possible.

DeafEyeJedi

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C mount lenses 5x crop mode
« Reply #2 on: August 14, 2015, 11:19:39 PM »
Nice! Post pictures of your set-up if possible?

Or perhaps some footage samples with that lens? [emoji4]
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dfort

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Re: C mount lenses 5x crop mode
« Reply #3 on: August 15, 2015, 06:53:07 AM »
There was a topic about this a while ago. Too bad most of the photos and videos are now dead links. Here's my setup:



This is from a customer review I wrote for an 8.5mm lens. The most expensive lens I got was a 4.8mm and the cheapest was a 35mm 1.7 Fujian which costs about $20 and has a following on flickr.

The 35mm lens can fill the APS-C frame while the 8.5mm and 4.8mm lenses are only useful for crop mode. These aren't super sharp lenses but they are fun to experiment with, especially the 35mm Fujian which got a reputation for its creamy bokeh when used wide open.

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dpjpandone

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Re: C mount lenses 5x crop mode
« Reply #4 on: August 20, 2015, 04:59:52 PM »


is the one i use, I also have a 12.5-75 tokina c-mount that i don't really use anymore, if someone would like to play with it, pm me.

The EOSM in 3x crop mode is closest to 1/2" sensor, or 8mm film so those are the types of lenses to look for. the 8-48 is the equivalent of 24-144mm with a maximum aperture of 1.0, and parfocal zoom! It's pretty awesome...

Dfort, can we see some footage with your 4.8mm?

dfort

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Re: C mount lenses 5x crop mode
« Reply #5 on: August 21, 2015, 05:02:35 AM »
Ha ha--Isn't that the photo that's in ebay?

You're making me work. I can compile ML but believe it or not I have never uploaded a video to YouTube or Vimeo. I got a few C-mount lenses when I got my first EOS-M because I wanted to shoot some raw video on the cheap. Well, it turns out that raw video on the EOS-M isn't practical for shooting documentaries so I haven't used these lenses much. However, after doing a little out the window lens test I might change my mind. It seems raw video on the M has gotten much better and the tools can easily deal with the dreaded pink focusing pixels.

You want to see what it looks like through the 4.8mm lens? First of all this is what most people expect so I won't disappoint anyone:


The above image is what it looks like on the full APS-C frame. Almost a fisheye but not really.


This is a frame of 3x crop MLV raw converted to dng with mlv_dump and run through ACR. Not too wide is it? In fact it is almost the same as the 22mm kit lens on the APS-C frame.


This is what the 22mm lens un-cropped looks like for comparison. It is almost as wide as the 4.8mm in crop mode. Obviously the light was changing rapidly as I was slowly thinking what would be good to post.

Finally--the 8.5mm


If you do the numbers would think that the 8.5mm lens would match the 22mm closer because 8.5 x 3 = 25.5 but it doesn't. Maybe it is a 5x crop factor? 8.5 x 5 = 42.5. That pretty much matches the field of view with the 18-55mm zoom set at around 40mm un-cropped.

So we got these cameras with the big sensor sizes to shoot shallow depth of field and now we're using a tiny section of that sensor to get better looking raw video. Humm--the 4.8mm doesn't even have a focus adjustment.
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dpjpandone

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Re: C mount lenses 5x crop mode
« Reply #6 on: August 21, 2015, 02:58:39 PM »
Yes that is the ebay picture!

What resolution was your MLV capture? if it's smaller than 1792 that would explain the extra crop. If you do a frame grab of h264 in crop mode it should look like a 14mm right?

dfort

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Re: C mount lenses 5x crop mode
« Reply #7 on: August 21, 2015, 03:50:11 PM »
Oops, I forgot to list the resolution.

The raw video frame size was 1280x720. I find that easily scales up to 1920x1080 and is about the maximum the EOSM can handle for MLV with audio.

I'll check out H.264 crop mode and report back.
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Kharak

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Re: C mount lenses 5x crop mode
« Reply #8 on: August 21, 2015, 05:52:04 PM »
If you are recording 3x Crop mode in 1280x720p

That will add extra crop to your image.

Crop mode used at its fullest extent is 3x of your Sensors entire pixels. I don't know the exact specs of the EOS M but I would guess 720p in 3x crop is like adding another 2x crop.

But I can understand recording at max resolution in 3x Crop mode is hard for your cameras write speed. But could you try increasing the resolution to the max in 3x crop mode and see how the 4.8mm looks like?

once you go raw you never go back

dfort

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Re: C mount lenses 5x crop mode
« Reply #9 on: August 21, 2015, 09:24:21 PM »
I'm still learning this stuff. Here is what the 4.8mm looks like in H.264 1920x1080 with the Crop mode turned on:



So I take it that this is the 3x crop and with the 1280x720 MLV settings it turns into a 5x crop. The OP was about 5x crop so I assumed that the topic was about raw video.

In any case, as you can see it is way wider in 3x crop. I have used 3x crop when shooting with prime lenses and was too lazy to switch to a longer lens. With a 24mm lens it is like having a 24-70mm zoom, except with nothing between the two ends.

Back to the 4.8mm lens, it is a fixed focus lens and gets rather soft wide open at f1.8. I don't think that increasing the H.264 bit rate would be of much benefit with this lens.

If you are recording 3x Crop mode in 1280x720p

That isn't possible, crop mode is only for 1920x1080 -- or raw video with the Canon menu set at 1920x1080.

By the way--I read somewhere that the APS-C sensor is close to Super35mm while the 3x crop mode is like Super16mm and 5x crop raw like Super8mm. So the EOS-M is like owning three film cameras.

[EDIT: Just out of curiosity I checked the field of view with the 11-22mm zoom and the 4.8mm in 3x H.264 crop mode is a bit wider than 14mm. Closer to about 12.5mm.]
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Datadogie

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Re: C mount lenses 5x crop mode
« Reply #10 on: August 30, 2015, 03:02:49 PM »
Is an fd mount the same as an ef mount. Bear with me.
I have a c mount 12.5 - 75mm f1.6 bought an adaptor on a whim. Macro only.
Now if I buy a fd adaptor with glass will this fit and work.
C mount + c mount to ef + fd to ef.
Or with the extra thickness of having two adaptors put me back to square one.
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dfort

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Re: C mount lenses 5x crop mode
« Reply #11 on: August 30, 2015, 07:24:38 PM »
C mount + c mount to ef + fd to ef.

I've seen adapters to fit EF and FD lenses to a C-mount camera but you're talking about going the other direction? What's the role of the FD to EF adapter in getting this to work? That adapter is for mounting FD lenses to EF mount cameras--the adapter you referred that has the lens in it.

Note that all of the C-mount lens photos I posted were done on an EOS-M which uses an EF-M lens mount so I just used a C-mount to EF-M adapter.
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ansius

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Re: C mount lenses 5x crop mode
« Reply #12 on: August 30, 2015, 08:00:41 PM »
Is an fd mount the same as an ef mount.

No it is not, FD mounting flange is closer than EF's so for it to be mounted on EF it has to contain optics, or it will not be focus able to infinity. There are large amount of cheep and grate FD glass, but it is useful only on m4/3 or E-mount and EOS-M (like this one - https://www.lensadaptor.com/canon-fd-canon-eos-m-adaptor).

so just look for FD to EOS-M adapters, there are many different ones. There is also rumor of Metabones making FD SpeadBooster to EOS-M, but as market would be rather small, I'm not sure it will ever become reality.
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Datadogie

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Re: C mount lenses 5x crop mode
« Reply #13 on: August 30, 2015, 08:54:24 PM »
I have the lens and c fitting to the t3i. Obviously its way out of focus. I thought maybe just maybe I could add the fd adaptor with the corrective lens to get the focus working. That's why I'm asking if they are both the same fitting. If not do you get such a thing as c to fd then I could try the fd to ef adaptor.
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dfort

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Re: C mount lenses 5x crop mode
« Reply #14 on: August 31, 2015, 02:52:58 AM »
Those adapters won't work, the flange focal distance between C-mount and FD lenses is very different. To get a C-mount lens working properly on an EF mount camera would be very difficult, some may say impossible, because you need to have the mirror locked up and it would be recessed far into body.

There are adapters available, but you can't focus to infinity. They are only good for macro work.

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ansius

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Re: C mount lenses 5x crop mode
« Reply #15 on: August 31, 2015, 09:40:30 AM »
EOS-M uses so called EF-M mount with flange distance of 18mm and C mount is 17.526mm so there should and is a straight C to EF-M adapter (like this http://www.ebay.com/itm/Fotga-C-mount-Lens-to-Canon-EOS-M-EF-M-Mirrorless-Camera-Body-Adapter-Ring-/261148049674). Why the hassle?
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