BetterPhoto Q&A
Category: New Answers

Concerned at buying the right Lens

In my sights is the Canon EF 17-35mm f4 USM L Lens.

I am convinced that it will fit the two bodies, but, as I suspect the 50d has a crop frame sensor, what will be the issues I will face with this Choice ?

Or, am I wrong and it will work fine ....... !

Thank you very much for your time, input and advice.

Also apologies, if my question seems dumb !! I am an enthusiastic, yet complete amateur photographer.

Nick

To love this question, log in above
March 22, 2015

http://www.imaging-resource.com/news/2013/09/30/rokinon-14mm-f-2.8-lens-review

To love this comment, log in above
March 22, 2015

When you mount the 17-35 on the 5D (full-frame sensor) body, the lens behaves optically just as it should, as it was designed to, ie, in terms of the circular image the lens is projecting onto the rectangular sensor inside the camera, at any given focal length... The larger, full-frame sensor captures as much of that lens' projected image as possible.

At the 17mm / wide end of that lens, mounted on the 5D, your *horizontal* field of view in a captured image (expressed as an angle of "how wide the scene appears to be") would be about 93 degrees wide. (A pair of human eyes sees somewhere less than 180 degrees wide, horizontally, looking ahead.)

When you go mount that same lens on the 50D (crop-sensor) body, everything still works (autofocus, etc.) -- but the amount of the lens' projected circular image being captured by the now-smaller rectangular sensor inside the body, is naturally, smaller, which effectively means your captured image now appears narrower than before. The resulting captured scene, if the lens were at 17mm on your 50D, would be around 67 degrees wide (horizontally) instead of 93 degrees wide. Nothing but the camera body (and sensor inside) changed...

67 degrees is about the same angle/field of view that a 27mm lens would produce, when you mounted a 27mm lens to a 5D (full-frame) body. You'll hear all of this expressed as the 1.6x crop factor -- meaning, a 17mm lens performs like 17mm (in terms of how wide the image is) only when mounted to a full-frame sensor camera. When placed on a crop-sensor camera, the same 17mm lens will produce a narrower-looking image, which looks like it what you'd capture with a 27mm lens on a full-frame sensor camera... 17mm x 1.6 = 27.2mm.

The 1.6x factor tends to hurt you at wide angles (ie, it is always eliminating some of the lens' wideness -- you buy a wide angle lens to capture wide scenes, right? Yet the ultrawide lenses really aren't ultrawide at all, if mounted to a crop-sensor body!) But then the crop-factor can turn out to help you at long zoom ranges -- if you put a 300mm lens on your 5D, you get the standard angle/field of view designed for that lens; about 7 degrees wide, horizontally... But when you mount that same 300mm lens on the 50D/crop-sensor body, you then get a narrower field of view captured (around 4 degrees), effectively the field of view that, to get on a full-frame sensor 5D, you'd need a big 480mm lens to produce!

To love this comment, log in above
March 23, 2015

A lens to consider would be the Tokina 11-16mm /2.8 DX II
Some points about the Lens:
Aperture Range: f/2.8 to f/22
Designed for Cameras with APS-C Sensors
Internal Focusing AF Motor
One-Touch Focus Clutch Mechanism
Two Aspheric Lens Elements
Two Super-Low Dispersion Lens Elements
Multi-Layer Coating
77mm Filter Thread
Now on the crop factor body this lens will be 17-27mm
This is a professionally sharp lens, I would check this lens out at your camera store.
Best of luck,
Jeff

To love this comment, log in above
March 23, 2015

UB.

To love this comment, log in above
March 24, 2015

You can get special lenses made just for crop-body cameras, that are built to deliver results similar to "normal" lenses designed on a full-frame assumed camera.

For instance. Canon has the 16-35 EF lens. This will mount to Canon's crop-body cameras as well as Canon's full-frame cameras. On a full-frame, it will deliver true 16-35 images / field of view. On a crop-body, it will deliver ~ 25-56mm images / field of view.

However, Canon also makes the 10-22EF-S. EF-S can only safely fit onto a crop-sensor camera body. You might think "that lens must give a staggeringly wide scene, at 10mm -- going into fisheye territory..." -- but, remember the 1.6x crop factor still applies here -- the 10-22EF-S is made specifically to deliver results (on a crop-sensor-camera) of a 16-35 lens (when a 16-35 is mounted on full-frame.) 10mm x 1.6 = 16, 22mm x 1.6 = 35.2.

To love this comment, log in above
March 25, 2015

The Tokina 11-16mm f/2.8 II is really made for crop body cameras:
When used on a DX camera, it gives angles of view similar to what a 17-24mm lens. You have to be careful if you switch
to a full frame camera body- because of the lens you are using now.
Let me know if you have any questions.

Jeff

To love this comment, log in above
March 25, 2015