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laco
05-09-2012, 03:16 PM
I think this forum already collected all the negative aspects of pairing a Canon EF mount with a 16mm wide sensor.
But haven't seen the positive aspects of "cropping" out the middle of these lenses. Here I collected some things that came in to my mind:

Sharpness Lenses are sharper in the middle, and image sharpness starts degrading as you look at the corners. On the BMC you will get edge-to-edge sharpness even with wide aperture.

Vignetting - Canon 50mm 1.2 at 1.2
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As you can see, on a full frame sensor you will lose -2.5, -3 stops of light at the edges, on the BMC you won't have any light loss.
Of course some indie productions will miss vignetting, but:
- for me it was always hard to adjust the vignetting of different lenses in post to each other
- some productions will need a picture without any vignetting (for example greenscreen work, where the BMC will shine because of the uncompressed RAW recording. VFX guys will thank you for recording vignette-free images)

Distortion - Canon 14mm 2.8 II
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You can see distortion mostly at the edges. You will get less to none distortion on the BMC.

Chromatic aberration/B]also happens mostly on the edges. Sadly I could not find test images.

[B]Fast, cheap telephoto lenses A 135mm 2.0 lens will give you the same field of view, as a 310mm lens on a full frame sensor. With a f2.0 maximum aperture, which is awesome. I can see some productions, where the BMC will be rented only for the telephoto shots.

Original images are from the great the-digital-picture (http://www.the-digital-picture.com/) site

nickjbedford
05-09-2012, 05:19 PM
Btw, your images don't work.

I agree though. There's some nice benefits to shooting on a smaller sensor. The crop factor is only an issue when you want to shoot wide, and for me personally, I won't be shooting that wide, only on the odd shot.

* Your effective focal length is roughly doubled (or 1.4x if you're used to APS-C crop already). My 17-55mm lens gives me 125mm of reach now.
* You don't need to stop down on a large sensor to get a more pleasing mid-range depth of field, but its still shallow enough to be pleasing, since you're moving backward to frame the same shot.
* As above, your lenses are designed for large sensor, so before moving to cine lenses, you're getting the sweet spot of these.

I'm personally not worried in the slightest at the crop factor's effects.

mbeck
05-09-2012, 06:23 PM
I am a little curoius about the assumption that you will get better preformance out of the lenses by only using the sweet spot. Isn't it the case that we will be squeezing more resolution out of a smaller area as well? Doesn't that have a negative impact on image quality?

Tim Joy
05-09-2012, 07:40 PM
This is true except when you want a very wide angle, as the shorter focal length required to match FOV to a larger sensor cam will inherently have more distortion.

nickjbedford
05-09-2012, 07:51 PM
I am a little curoius about the assumption that you will get better preformance out of the lenses by only using the sweet spot. Isn't it the case that we will be squeezing more resolution out of a smaller area as well? Doesn't that have a negative impact on image quality?

Hmm. You are relying on the qualities of your lenses, but most decent photographic lenses are probably sharp enough for the pixel pitch of this particular sensor, I'd hazard a guess. Correct me if I'm off though.

Paul Stephen Edwards
05-09-2012, 08:00 PM
I'm with you, Nick. Most factors that impact my images negatively tend to be related to lighting or composition, not sensor size.

Love the work on your website, BTW.

nickjbedford
05-09-2012, 08:28 PM
I'm with you, Nick. Most factors that impact my images negatively tend to be related to lighting or composition, not sensor size.

Love the work on your website, BTW.

Thanks Paul!

Yeah, the sensor's dynamic range and video format are the most important aspects of the BMC for me. You can otherwise work around things like crop factors. If s16 film is used in feature films, then crop is obviously not a show stopper :P

Andrew
05-09-2012, 08:47 PM
I am a little curoius about the assumption that you will get better preformance out of the lenses by only using the sweet spot. Isn't it the case that we will be squeezing more resolution out of a smaller area as well? Doesn't that have a negative impact on image quality?

You're right. It is nice that the sharpest part of the lens is the center and the BMC will use that, but we'll also be "squeezing more resolution out of a smaller area" like you said.

I'm excited to test this out, but I think most good quality EF glass should be fine, after all they were designed with high megapixel cameras in mind.

Just a quick calculation, a FF 3:2 sensor is 6.15 times larger than the BMC 16x9 sensor. The BMC sensor is roughly 3.3 megapixels. 3.3 x 6.15 = 20.29 megapixels. So if your FF lens resolves well on a higher than 20 megapixel FF body, then it should be no problem with the BMC especially since we'll be using the sharp center portion of the lens.

If you plan to use EF-S lenses, you'll have to make sure sharpness is up to your standard as many will not be up to the task.

nickjbedford
05-09-2012, 08:57 PM
If you plan to use EF-S lenses, you'll have to make sure sharpness is up to your standard as many will not be up to the task.

I'll be using a 17-55mm F/2.8. Mostly the same as 24-70L without the metal construction. I'm not sure I would use the budget kit lenses, though John Brawley's test footage didn't seem to have obvious aberrations, distortion etc. Something to test anyway.

mbeck
05-09-2012, 09:23 PM
Thanks Paul!

Yeah, the sensor's dynamic range and video format are the most important aspects of the BMC for me. You can otherwise work around things like crop factors. If s16 film is used in feature films, then crop is obviously not a show stopper :P

I totally agree! I wrote a blog post about this topic as soon as the camera was announced.


There are many opinions about the BlackMagic Cinema Camera’s sensor size, and what size is the minimum for that cinematic look. Here is mine.

The world changed when large sensored DSLRs exploded on the low budget cinema scene. Since then the seemingly insatiable desire for razor thin DOF (depth of field) has been over whelming the industry. It seems everywhere you look on Vimeo all you can see are focus-chasing, one eye in focus, one eye out of focus footage. The craze has led some to believe that you can’t get that cinematic look with anything less than a full frame camera with a f1.2 prime wide open. This simply is not the case.

The rest of the post can be read here: http://wp.me/p2oP5O-z

adam777
05-09-2012, 09:44 PM
I'll be using a 17-55mm F/2.8. Mostly the same as 24-70L without the metal construction. I'm not sure I would use the budget kit lenses, though John Brawley's test footage didn't seem to have obvious aberrations, distortion etc. Something to test anyway.

Canon 16-35mm L is so much sharper than the creamy 17-55mm, but you have the extra length ...

nickjbedford
05-09-2012, 10:27 PM
I totally agree! I wrote a blog post about this topic as soon as the camera was announced.



The rest of the post can be read here: http://wp.me/p2oP5O-z

I read it a little while ago :)

Gwangjuboy
05-10-2012, 01:05 AM
The IS/VR in many of the EF/S lenses is going to be very useful. Not being to get so wide (ironically the fault of having an EF mount and crop) with many lenses will make this function if they do activate it in the camera essential handheld.

laco
05-10-2012, 01:11 AM
Btw, your images don't work.

still don't work?

nickjbedford
05-10-2012, 01:30 AM
still don't work?

All good now.

laco
05-10-2012, 02:04 AM
If you're afraid that you will lose sharpness because of the cropping, I found something to put the Canon lenses to a test.
This was shot on the Scarlet at 3K which results a m4/3 cropping, approximately 2x crop factor. Oh, and of course Canon lenses:)

https://vimeo.com/39472846
Do you find it sharp enough? If yes, you don't have to worry about this one.
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original video was shot by Richie Trimble

vealti
05-10-2012, 11:23 AM
I now have a 160mm to 460mm 2.8 lens that only cost about $600.

Brian@202020
05-10-2012, 11:55 AM
Another benefit is that if you are looking for a wide lens you might be able to get away with a fisheye lens since a lot of fisheye lenses distort at the edges.

Brian@202020
05-10-2012, 12:00 PM
I now have a 160mm to 460mm 2.8 lens that only cost about $600.

I love long lenses. I once did a 16mm shoot with 300mm lens with a 2x doubler, making it 600mm. I was over 4 blocks away to get the people head to toe in shot. The shot was them walking toward the camera. For about 100 feet they stayed roughly the same size in frame. To date it one of the most beautiful shots I ever done.

pcenginefx
05-10-2012, 12:14 PM
If you're afraid that you will lose sharpness because of the cropping, I found something to put the Canon lenses to a test.
This was shot on the Scarlet at 3K which results a m4/3 cropping, approximately 2x crop factor. Oh, and of course Canon lenses:)

https://vimeo.com/39472846
Do you find it sharp enough? If yes, you don't have to worry about this one.
62
original video was shot by Richie Trimble

Hmmm...doesn't look work safe :)

Michael Bergstrom
06-11-2012, 04:30 PM
I'm going to utilize the crop factor in a big way. My business partner and I have been slowly rebuilding a wildlife stock library for a client. We've been using the Sony F3 and FS100 with a 100-400mm L with a doubler. I'm planning on using the 100-400 with the 2x electronic doubler on the BMC camera to give me a 2.5K image at 1600mm. Hello bear mug shot eating a salmon.

Cornelius
06-11-2012, 05:23 PM
Hello bear mug shot eating a salmon.

Lol

morgan_moore
06-13-2012, 02:21 AM
..If s16 film is used in feature films, then crop is obviously not a show stopper :P

Its not - its the mix of the crop with the huge flange depth

Osslund
06-13-2012, 04:23 AM
The only beef is that with regards to the sensor size this camera could take so many lenses if it had such a mount. But it's better if BMD gets the camera out the door instead of delaying it. I don't see the crop as a downer just the EF mount if you consider what could have been.