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Q & A - Our Archives

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Q: Our students often ask what's the difference between a full-frame camera and one with a crop factor?

A: Without getting into a lot of technicalities, SLR-type cameras that have a crop factor have a sensor that's physically smaller than a 35mm negative. Since many lenses were designed f...or 35mm film, they project an image the size of a 35mm negative where the sensor is – and some of it falls outside the sensor (since it's smaller). The middle part is what's captured and is what you see through your viewfinder or on the LCD. In effect, you're seeing the middle portion of what the lens captures. That increases the effective focal length by whatever the crop factor of the camera is. On many Canon SLRs, for example, it's 1.6x. Simply multiply the focal length of the lens by the crop factor to get the effective focal length of what you'll see. For example, a 50mm lens with a 1.6x crop factor gives you an 80mm effective focal length.

For telephoto photography, the crop factor works to your advantage. A 200mm lens gives you a 320mm field of view. But for wide angle work, it works a bit against you – a 17mm lens becomes about a 27mm lens.

A couple other pros and cons: a full-frame sensor (one with a 1.0x crop factor) tends to have lower levels of digital noise. It will also be a lot more expensive. Sensor size also affects the degree of depth of field so a full-frame sensor can give you shallower depth of field at a given aperture than a crop-frame sensor.

So is one better than the other? Not necessarily. For most of us, a crop-factor SLR-type camera probably has more advantages than disadvantages (particularly cost), but if extremely low digital noise, very wide-angle photography, or very shallow DOF is important, a full-frame sensor camera may suit your needs better.


--response submitted by our Lead Teaching Assistant, Eric Johnson

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Q:  What's a Model Release and where do I get one?
 
A:  A Model Release is a form for people to sign so you can use the pictures you've taken of them. That's the simple answer!
 
There are different types of model releases for different situations and there are lots of long discussions on how and when you need a model release.  A short and simple rule of thumb is that if you want take a picture of a recognizable person and want to use it commercially (sell it or use it for business purposes) you'll need a model release.  It's also a very good idea to have a model release of a picture of a recognizable child (signed by their parents) before you post that picture to the Internet or use it in any way. And, out of courtesy, it's recommended that you have permission to post pictures of people on the Internet.
 
An excellent resource for several different types of model releases, including nine languages, is the American Society of Media Photographers web site: 
 
And, if you'd like a small pad of paper releases to keep in your camera bag, here's a spot to order those:  http://filmphotographyproject.com/store/model-release-form-pad-50-sheets
 
Or, if you prefer an electronic approach, check out Easy Release app for iPhone/iPad
 
or the Android version:
 
Finally, if you'd like to read a rather detailed discussion about needing model releases, here you go!
 
-- response submitted by Beverly Richards Schulz, Photography Instructor 
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Q: What’s your favorite lens for portrait work and why?

My favorite portrait lens for head and shoulder shots is my Canon 85mm F/1.8 lens. I lov...e this lens for head and shoulder portraits because I can use it indoors or outdoors with excellent results. Being a fast lens, with a very large aperture of F/1.8 it creates a wonderful shallow DOF to help blur the background, keeping all the focus or attention on my subject.

Also, being a fast lens it lets in enough light to use indoors where the lighting isn’t always the best for portraits. This lens doesn’t work well for full body or three-quarter portraits as it is a prime lens (no zoom), so I have to zoom with my feet. Indoors, that’s not always an easy option.

So my other favorite portrait lens is my Canon 24-105mm F/4 L lens. I love to use this lens because I can zoom between focal lengths to create full body, three-quarter length, or even head and shoulder portraits with ease. It is not a fast lens, meaning it has a smaller aperture than my 85mm F/1.8 lens and lets in less light. It does a great job indoors as well as outdoors because it is an L (professional quality) lens.

Since this lens has a wide angle of 24mm, I stay away from that end of the lens as using a focal length less than 50mm can cause some distortion. Canon has a multiplication factor of 1.6, so I can start using this lens at 32mm (32mm x 1.6 = 51.2mm). This lens also allows me to create a wonderful shallow DOF. I find both of these lenses to do an excellent job on portraits.

--Response by TA Kimberly, Secrets of Better Photography Teaching Assistant
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