FOV - SLR vs. PL

[Joel Kaye]

Does a 35mm PL mount with a focal length of 50mm show the same FOV as a 50mm SLR lens?

I'm just verifying in my mind that the reason to buy Cine lenses over SLR has more to do with sharpness, contrast, bokeh, breathing, CA, easier to pull focus etc. but NOT crop factor as the crop should be the same. Have I got that correct?

[Stephen Williams]

Does a 35mm PL mount with a focal length of 50mm show the same FOV as a 50mm SLR lens?

I'm just verifying in my mind that the reason to buy Cine lenses over SLR has more to do with sharpness, contrast, bokeh, breathing, CA, easier to pull focus etc. but NOT crop factor as the crop should be the same. Have I got that correct?

Hi,

A 50mm lens is always a 50mm lens. On the same camera the FOV will be about the same. About you ask? a 50mm lens is probably not exactly 50mm!

Stephen

[Michael Schrengohst]

Those are good questions. I intend to get the Nikon mount and use all my Nikon mount lenses to get my feet wet. I want to rent some cine lenses and then keep my eye on the RED lenses. Our initial shoots will probably be on greenscreen for a web project. Eventually we will move over to our commercial side and see how the RED does.

[Paris Remillard]

Yes. 50mm is 50mm whether it is on a 1/3" chip, 35mm, or 4x5 film. The FOV is determined by the size of the format one is capturing to. The best way, for me at least, to think about it is to picture the windowed sensor on the RED. If you have a 50mm lens on the camera that covers the full sensor, then switch to the super 16mm sized windowed sensor, you are literally cropping out the center of the image. The size of the overall image didn't change. It it the size of the area that you are looking at that changed. Which makes a given focal length appear to have a narrower FOV on a smaller format (thus, being more magnified or telephoto). This is the same with all formats.

What is different among lenses that are the same focal length but made for diffent formats, though, is the size of the image circle. A lens made for 16mm will not make a big enough image to cover the whole 35mm frame(in most cases). It doesn't need to because a 16mm frame is only 1/4 the size of 35mm. It will make a circular image(or vignette) in the middle of the frame. However all 35mm lenses will cover 16mm because the image circle will be much bigger than the 16mm format.

So, to your original question. The FOV will be the same given that the format is the same. However, the image circle of an SLR lens is in most cases going to be bigger than PL mount lenses because the 35mm stills format is 24mmx36mm. Whereas 35mm cine is (approx.) 18mmx24mm, or half the size of stills format. Also, PL mount lenses are made for both 16mm and 35mm, so all PL mounts won't inherantly cover 35mm.

When I was trying to learn about formats, it helped me to take out a ruler and literally make cut outs of different format sizes on pieces of paper and put them over an image to see the crops. If you just take a photograph that you have and assign it an arbitrary focal length, say 50mm, and then put a 4x5 inch box around it and then 6x7cm box, and then a 24x36mm box, and then an 18x24mm, box and so on, it should make sense. The picture itself doesn't change, as the focal length doesn't change. It is simply how much of that picture you are looking at.

Sorry if I get too wordy, my brain goes faster than I type. Anywho, hope this helps.

[Joel Kaye]

The picture itself doesn't change, as the focal length doesn't change. It is simply how much of that picture you are looking at.

Yeah - perfect sense. I guess I knew that... but I think I needed it repeated. I'm very curious to do some of these SLR vs. Cine lens comparisons. It would be cool if there was some of that at the NAB booth.

This also brings up the possibility that newer low contrast G lenses for digital camera that aren't full frame(24mmx36mm) may work on RED provided we can adjust the aperture somehow.

[Paris Remillard]

<has more to do with sharpness, contrast, bokeh, breathing, CA, easier to pull focus etc. >

I haven't done tests personally or even looked at too many charts to compare, but I really don't think that Cine lenses are any sharper than stills lenses. Contrast and bokeh are always variables on cine or stills lenses. The real advantages of cine lenses are focus and iris gears and lack of breathing. Which are big advantages. But the reason that they are so expensive is economics. Period. Not that they are so much sharper or better. Whereas Canon or Nikon could sell maybe tens of thousands of a given lens, Cooke could sell tens.

Canons or Nikons wills be plenty sharp. They'll breath. They'll be hard(er) to focus. They'll each have their own characteristics, even from one lens to another within a given brand, as will Cooke and Zeiss. But they'll be plenty sharp.

[chuck colburn]

Nice wording parisrem. Simple, concise and easy to understand. One minor note though. S35 is more like 70% the size of 35 still as you would measure the difference by the diagonals of the frames.

[Paris Remillard]

Good call, Chuck. Thanks. I'm not always accurate but I try to sound convincing anyway.

I guess I should say half of the physical area. Or Half Frame format. That woulda been technically correct.

Also, there are so many variations of what constitutes "cine" sized 35mm that it's hard to be too accurate anyway, so I just avoid the specifics. It's too confusing. Anamorphic(Cinemascope) , Academy, S35, Techniscope....

[David Nardini]

... the FOV is determined by the size of the format one is capturing to ...

the following link should help :

http://www.canondv.com/industrial_bc...lculator1.html

[Mike the beginner]

The word perceived comes into mind with that question.


Mike the beginner