David W. Jones
Veteran
Maybe this will help you understand the differences between sensor size and lens use.
http://www.abelcine.com/fov/
http://www.abelcine.com/fov/
GH2 crop factor 1.86x or 2x ?
- Thread starter Apefos Adapter
- Start date
Depends on the cameras they used to shoot with (IMDB often lists the cameras used), but if it's a fully funded feature film they are probably referring to a Super35 format camera.
All lenses are marked by their focal length (the distance required to focus an image at infinity focus) in millimeters. Doesn't matter what format the camera they are used with, so a 50mm lens is still a 50mm lens when used with ANY camera. ( a 50mm lens might be a telephoto "portrait" lens when used with a small format camera, or it might be a super-wide angle lens when used with a very large format camera, but it's still a 50mm lens )
Barry_Green
Moderator
Short answer: no.
Long answer: I'm not sure you understand the question you're asking. Lenses aren't "marked" in respect to any frame of reference. Lenses are rated as to their focal length. I think what you're asking is if they're marked in accordance to the field of view that the lens would deliver when attached to a photographic 35mm frame, and if that's the question you're asking, then no, NO lenses are marked in that way.
Lenses are listed as to their actual focal length.
The field of view you get, is dependent on the sensor size. A lens doesn't know what it's attached to, and it doesn't care -- it makes an image. Hold a lens up against a wall, and you'll see that it projects a circle of image onto that wall. The wall isn't a sensor, and the lens doesn't know what the sensor size is, or if it's a wall, or anything like that. The lens renders an image based on its focal length, and on its designed circle of illumination.
-Tom-
Active member
Thanks! I guess a lot of my confusion comes from reading too much forums and absolutely no actual filmmaking literature...I've read so posts like "50mm is probably the go-to lens for your DSLR video" and similar, it got under my skin apparently.
I need to get out of that mindset.
Bonus question - seeing that Helios 58mm has the same FOV like Lumix on 67, where does the 11mm difference come from then? Does the m42 to m43 adapter play a role here, or not?
I need to get out of that mindset.
Bonus question - seeing that Helios 58mm has the same FOV like Lumix on 67, where does the 11mm difference come from then? Does the m42 to m43 adapter play a role here, or not?
On the SAME camera the FOV will only be the SAME if the focal length of the lenses is IDENTICAL. So the ONLY way these two lenses would ever have the SAME FOV is by using them on DIFFERENT cameras.
A 58mm lens will NEVER have the SAME FOV as a 67mm lens when used on the SAME camera.
FrameFarmMedia
Veteran
or if he was comparing the 58mm prime with a lumix zoom marked at 67mm it just goes to show how far off the focal length marks are on these electronic zooms.
-Tom-
Active member
But if you look at my test picture you'll see that 58mm lens has a FOV that's identical to 67mm, and when I put the Lumix lens on 58mm the FOV is nowhere near.
So I guess I'm asking, why is there a difference between Helios 58mm and Lumix 58mm on the same camera, rather difference by 11mm?
So I guess I'm asking, why is there a difference between Helios 58mm and Lumix 58mm on the same camera, rather difference by 11mm?
David W. Jones
Veteran
This, and many lens manufactures round off their printed focal length. For example... They might say the focal length is 50mm, but in reality the lens might be 46.8mm
The focal-length lens markings on the Lumix Zoom are not accurate. If the focal length was the SAME, then the FOV would be identical.
stoneinapond
Veteran
I'm sorry, that statement makes no sense. The Helios on a m43 camera will have about the equivalent field of view of a 116mm lens, but with the 58mm focal length aesthetic. I won't have access to my Helios and a Pana zoom until the weekend, but I will do a short test then that will perhaps make your conundrum clear.
-Tom-
Active member
Yeah, I guess it's a little bit off. Tried to fine-tune the Panny zoom to 20mm, can't seem to do it, I turn the barrel in mini increments but the EXIF data shows 19mm and 22mm in that area, no in-betweens.
-Tom-
Active member
I just showed you the test where Helios 58mm has the same FOV like Lumix zoom at 67mm. That's all that matters really. Helios 58mm on GH2 has 116mm field of view if you're comparing it to photographic 35mm frame.
Barry_Green
Moderator
As said before, 25mm does not always equal 25mm. The manufacturers ballpark it, sometimes they round up, sometimes they round down. I've got, I think, about seven 25mm lenses here, and the focal length isn't identical on any of them. They're all in the general ballpark, but they're not identical to each other.