View Full Version : Idiot's Guide To Lenses?
04-17-2007, 09:50 PM
Okay, I'm a complete newbie when it comes to all of this lens talk. I'm a reservation holder but I haven't ordered any lenses cause I just don't know what to do. I've only ever used regular video camera's with fixed lenses like DVX and HVX so the whole lens thing is new to me. Can someone please give a sort of idiot's guide to lenses. What is the disadvantage of using DSLR lenses instead of Cine Lenses? What does it mean when a lens "Breathes" too much? This is kind of embarrassing because I can see people saying "This guy doesn't even deserve a RED camera if he doesn't know anything about lenses." I know, but I want to learn. I know about Iris and Aperture and the basics of photography. Just not lenses in a cinematic area. Thanks in advance!
03-10-2010, 07:42 PM
I'm in the same boat and wondered if you ever got a reply?
03-10-2010, 08:22 PM
Here are some things to look for when you are checking out a lense:
1. Minimum and Maximum T-Stop:
Close to F-Stop but this has a more direct relation to how much light the lense allow in and also how shallow or deep the depth of field can become.
2. Close Focus:
What is the minimum distance an object can be from the lense and be in focus. Very important to know this and how this relates to the type of compositions you want.
When you change the focus on a lense the frame will zoom slightly. We call this breathing. Better lenses do this as little as possible. Generally zooms do it more than primes.
How sharp does the lense get. Some lenses are sharper in the center and soft at the edges. Often people prefer softer lenses for some jobs and sharper for others.
How even is the exposure across the frame. In most cases more even is better but this is also subjective.
How accurate are the mechanics of the lense. How easy is it to rack and keep focus. How accurate are the focus marks and do they stay accurate. Does the lense stop at infinity or focus beyond infinity (I personally would like it to stop dead on infinity.)
7. Chromatic Aberation
An optical effect wherein some wavelenghts of light will be bent more than others by certain types and shapes of glass. What you'll see is an image where the colors don't fall in the same spot, like a 3 color printing process with the different colors slightly misaligned. Chromatic aberation is generally unattractive on an image but I guess this is subjective.
What shape does the light create when it's out of focus. Different for every lense and depends on the shape and number of aperture leaves at different F-stops. Totally subjective, very important.
How is the frame shaped exactly, does it pinch at the edges etc. Usually most apparent with wide lenses.
10. Color Rendition/Matching
Less of an issue if you have a good colorist, but important to look for and understand.
How does the lense react to a light source hitting the actual glass. Depending on the type of glass and how it is coated, and the condition of the coating. This affects contrast and also the shape of flares on you image.
I probably missed a few things. The important thing is: I use different lenses for different jobs depending on look, specs and cost. I personally love older glass on digital cameras, but I always do a ton of testing before I try to shoot with something I haven't used before.
03-10-2010, 08:29 PM
Go to local library - college library and look for some photography books. Unfortunately I don't remember the title but a book turned me from completely ignorant to well primed when I started 25 years ago. I wish I had that book- typical for books I lent it to somebody and never got it back...
I guarantee you that all questions you asked would be answered.
03-10-2010, 09:14 PM
The first post in April, 07. This forum may not always be quick but it comes through in the end :)
BTW great post Ian
03-10-2010, 09:21 PM
12- Field curvature
14- Modulation Transfer Function (MTF)
15- Subjective Quality Factor (SQF)
Check following links;