Lens Overview for Beginner

[binary_syntax]

Hey everyone,

I'm a big-time beginner, but am excited about getting into photography and filmmaking.

I understand f/T stops, focal lengths, etc. but was wondering if someone wouldn't mind explaining differences in lens sizes. Which lenses will work for the Scarlet 3K vs. S35 vs. FF35? What's the difference between a 16mm film lens and a 35mm film lens? Also, for motion picture cameras, will a 35mm lens work on a Super 35mm camera? I guess I just need to know how to measure lenses and see if they will work on a particular camera. I know some lenses will fit with a proper converter for the mount, but why does it sometimes change the focal length or depth of field?

Thanks alot, and I know this is a huge question that goes into a lot of detail, but I've never learned how to discern one lens from another (besides their speed).

~Jason

[Jared Caldwell]

Hello Jason! Welcome to ScarletUser!

Most of your questions can be answered by searching for a bit on the forum, but I know there is a lot of info to learn, so I will try to field as many questions as I can and leave the rest to those that are more technically savvy that I on the boards...

To begin with, all of the Scarlet bodies have interchangeable mounts except for the fixed lens Scarlet. This means you can use most lenses on each body, no matter what the brain you use.

This being said, the 2/3" Scarlet will have a crop factor when using 35mm lens. That means 35mm lenses will appear more telephoto on a 2/3" sensor than the 2/3" equivalent.

16mm is slightly larger than 2/3" sensors, but 16mm lenses are used on 2/3" lenses all of the time. S35mm (which is used in motion pictures) is larger than 16mm. FF35 is larger than S35mm. FF35 lenses will cover S35, but FF35 STILL lenses sometimes have more "breathing" than cine S35mm lenses. This means that the focal length slightly changes when you adjust for focus.

This is just a generalization to get you started. I am sure others will be able to go into more detail.

Enjoy. :}

[Stefan Christou]

Hey Binary,

I think what you're asking is what's the difference between lenses for different formats, fundamentally nothing really, a lens is a lens is a lens. That being said not all lenses were created equal.

The big difference between lenses created for one format over another is the amount of format it can cover. So 35mm lenses will be really big and work fine on any format smaller, as will medium format lenses. A lens designed to cover a 2/3" sensor or 16mm film (for example) wont be designed to cover a larger format and you'd basically get a circle of an image if you put it on a bigger format.

As Jared said, lenses designed for moving images have a different focussing mechanism than those designed for stills. As with stills lenses it doesn't matter that they "breath" so they can use the more simple (and cheaper) focusing mechanism.

Now other than that there is no real difference between a lens made for one format or another (aside from quality, which get's a lot more complicated.)

The thing that I think confuses people is that manufacturers front and state "equivalent focal lengths" this is basically marketing BS. But what they are referring to is field of view. So because smaller formats are more cropped than their bigger equivalent, you'd have to use a wider angle lens to give an "equivalent" field of view.

Edit: So to answer your question. Putting a lens on a different camera does not change its depth of field or focal length.

The problem is that when you use wider lenses you can do funny things to perspective like the size of a person's head at a given distance, compared to another person's at a different distance, might look odd. Also with wider lenses you get a deeper depth of field at any given F/T stop. So the 35mm depth of field people refer to is actually a product of the focal length of the lens rather than being a property of the format itself. The difference is that you can "choose" a longer lens for 35mm than for smaller formats as you'd be less cropped in, hence why people refer to 35mm depth of field even though they are really referring to a conscious choice they make over lenses and are actually in most cases referring to a choice of focal length they might make for a s35mm format.

The other thing that wider lenses can do more is distort and give a slight "fish eye" effect.

And the other advantage with lenses designed for big formats is that they themselves have to be big and hence gather more light. (Another edit: But the difference in light gathering is only useful if you also have a big format to catch all that light.)

As far as F/T stops are concerned they both refer to exposure but T stops are more precise. Let me explain... a T stop is a measurement of how much light is actually be passed through the lens at a given aperture. This takes into account how much light is lost in each element of the lens. F stops are a measure of the size of the hole in the aperture and nothing else. Aperture obviously has an effect on depth of field, so although a T stop is a more accurate measure of exposure than an F stop, an F stop is a more accurate measure of depth of field. Accurate exposure is more preferable though, but measuring the T stop of a lens is more complex than simply measuring the F stop, and hence more expensive.

I've gotta go do some work. So I'll let someone else explain about lens coatings, flair and the limits lenses can place on dynamic range.


I hope this helps.

Stefan

[binary_syntax]

Thanks a ton guys! There was definitely lots of information in there that helped clear up a lot of things! So if, for instance, I got a S35 Scarlet, I would have to find S35 cine lenses? I haven't seen lenses specifically for S35mm... And how do you know if a SLR 35mm lens would work on a S35 or FF Scarlet?

How do you mathematically determine the conversion scale from a lens to a sensor size? You said when putting a 35mm cine lens on a 16mm / 2/3" camera you get a cropped, telephoto image? How do you mathematically determine the new, cropped focal length?

If I can learn this, I'll feel much more at ease with lenses because I feel behind the curve right now.

Thanks again!
Jason

[Kyle Presley]

Binary,
You can put any lens on any of the brains essentially. Bear in mind though that the image circle of the lens varies. Any manual focus Nikon or Canon FD lens will work for s35mm or FF35, or 2/3" for that matter. C-mount lenses will work for 2/3". That said, there will be a crop factor to consider, as I know you are aware. To determine crop factor, start with full frame 35mm. The sensor dimensions are 24mm x 36mm. If you want to retain the same field of view of a given lens, say a 28mm wide angle on FF35, on S35, multiply by (roughly) 0.7. You wind up with 19.6mm, which would translate to an 18mm, which is the closest standard focal length. To get the 2/3" equivalent, multiply by 0.3. You would get 8.4, which translates to 8mm, again, the nearest standard focal length for 2/3". Hope this helps. Also, check out this thread:

http://www.scarletuser.com/showthread.php?t=2256&highlight=equivalent

[binary_syntax]

Hey thanks Kyle! That'll help out a lot. And thanks again Jared and DefStef! Lots of good info!

~Jason