35mm slr still lens v.s. 35mm cinema lenses
 

So I'm trying to get a set of 35mm slr lenses that are equivalent (in terms of FOV, AOV, image distortion) 35mm cinema lenses in the mid20 mm focal range. Is the still lens focal length proportional 1:1 to cinema lens focal length? If not , how do I calculate?

thanks

Hi Amos,

thanks for your mail. I thought it may be of general interest and was also almost the same topic, so I think I'll answer it here.

Let's take this one step at a time:
FOV (Field of View) and AOV (Angle of view) mean the same thing in practical terms. Which angle, seen from the front of the cam, does the picture cover. Now, the FOV or AOV is the result of focal length and size of the imaging sensor or film frame.

What the adaptors help you to do is get a depth of field (DOF) that matches the FOV. It is no problem to get good DOF on my FX1. I can just zoom in leaving the aperture open. However, the image is very compressed; meaning the AOV is very narrow. You will have very little feeling of depth in the picture.

With a 35mm adaptor you can have a shallow DOF even at wide angle. So you can have a feeling of perspective as well as selective focus.

Now, to come to the point: You can have that with any sensor size! But the problem is you would have to open the aperture further than possible. If I could open the aperture on my FX1 to something like Fstop of 0.95 and still get a good picture, I would not bother with an adapter. But I can't, hence the 35mm adapter.

The difference between 35mm and 35mm film is a lot less than the difference between 35mm film and a 1/3" sensor. If I stop my 35mm photographic lens down by one stop, I get roughly the same DOF at a certain FOV/AOV as I would get with a cinema lens.

So my advice is, I you buy a 35mm photographic frame adapter (most you will find here), then look into 35mm photographic lenses.

If you have the money to buy 35mm cine lenses, you get much less distortion and much better glass but less value for money (they are darn expensive). Then you will have to consider an adapter that allows you to use cine lenses (a few ones around the alt. imaging forum as well).

To answer your question from my point of view, I am not able to afford cine lenses, I go for Canon FD and I look at lenses for the photographic 35mm frame. If you decide to do the same, then get a 24mm for very wide angle with strong perspective or a 28mm for wide angle. Get a 50 mm or 55mm for standard situations and a 100mm for portraiture. That will cover your needs for the beginning.

But when you hear on the directors commentary of american pie 1 that their first choice when primary photography started was whether to use a 16mm lens, they were not talking about using a fisheye ;-) It is simply that the focal lengths don't convert and one should be aware of this. Instead of trying to find out what film people use and convert to photo focal length, talk to some pro photographers. There are so much more pro photographers around and they'll be able to give you a whole lecture on which lens to use. And no need to convert focal lengths.

If you don't have a photographer at your disposal, try this very nice page (a scanned Canon lens book) to see how you can use the lenses.

http://www.canonfd.com/lenswork.htm

Ok, sorry for talking so much, I sometimes get very exited about this stuff.

All the best,

Thomas

And, what I meant to add: no need to convert between Nikon mount focal length and canon FD or EOS mount focal length etc., they are all the same ;-)