Comments on: Camera Hieroglyphics Demystified: The Camera Lens

By: Emmanuel

Emmanuel — Fri, 25 Mar 2011 14:16:41 +0000

David, u are just too kind hearted doing all these for free, God bless u.

By: Ian Scholes

Ian Scholes — Sun, 04 Jul 2010 14:29:34 +0000

Excellent read,really helps as a amatuer wanting to make photography my future business.

By: Keith Walker

Keith Walker — Mon, 19 Apr 2010 02:09:32 +0000

The focal length of the lens is the distance from the plane in which the lens forms an image of objects at infinity to the node of emission. It’s a matter of physics and the formation of the image. So a 50mm lens has a focal length of 50mm no matter what size film or sensor it is focuaaing on. The difference is in the angle of view. A 50mm lens on a 24x36mm (35mm film) has an angle of view of 47 degrees which is roughly that of the human eye

the same lens on an APS-C sensor which is much smaller, 16.7×23.4mm has a much narrower angle of view, 32 Degrees TO get a similar angle of view to the film on an APS-C sensor you use a 35mm lens which on the sensor has an angle of view of 44 Degrees – near enough.

You will find the description of many digital cameras gives the ‘equivalent’ 35mm lens in desribing the apparent focal length of the lenses

An 18-70 kit lens for a DSLR is still 18-70 if it were to e fitted to a 35mm film camera such as a Sony/Minolta On the film SLR the 18mm length has an angle of view of 100 Degrees, extremely wideangle. However the identical lens on an APS-C sensor has an angle of view of 76 degrees so its film equivalent is a 28mm wide angle. (it is actually 27mm but the difference of 2 degrees in the angle of view is negligible)

By: marlon

marlon — Wed, 24 Mar 2010 10:07:18 +0000

Thanks a lot! I am a beginner and is learning well because of your online tutorials!

By: Tony

Tony — Sat, 20 Mar 2010 06:48:41 +0000

“Numbers in the 18-50mm range are classed as ‘Normal’ lenses and take photos that look similar to what you see with your eyes.”

Not really, Dave. 50mm lenses on a full frame digital roughly correspond to the field of view of the human eye. An 18mm lens is definitely regarded as an ultra-wide lens on a full frame digital, and all lenses up to 28mm are described as wide-angle in the literature.

Of course, with non-full frame digital cameras, the effective focal lengths have to be increased by a multiple depending on the size of the sensor to produce the same effect. So that on say, a Nikon 200 a 35mm lens will approximately produce the same results as a 50mm lens on a full frame digital like the Nikon D3.

Compact cameras have lenses of a much shorter focal length because they have much smaller sensors. Hence their greater depth of field and dearth of wide angle options.

These days, any discussion of focal lengths really has to be related to sensor size. And I thought it was a pain to have to remember equivalents in 35mm and medium format!

Good shooting,

Tony

By: Rusty

Rusty — Sat, 20 Mar 2010 01:17:24 +0000

Hello,

I am interested in your opinion/experience, or readers, on using film era lenses on DSLR’s. I am especially interested in the 4/3 system because I have four Minolta lenses & understand they can be used with any 4/3 camera, with an adapter. Would the film lenses be less sharp then the digital lenses? What dificulties/problems could I encounter?

By: andrea brooks

andrea brooks — Fri, 19 Mar 2010 22:13:08 +0000

HELLO MR. DAVID I STILL WANT YOUR BOOK PLEASE ,AND I AM GLAD YOU ARE BACK THANK FOR ALL THE TIPS ANDREA

By: Dee

Dee — Wed, 13 Jan 2010 10:15:32 +0000

I have found so much on here that has enlightened me to photography. Your tips are great especially for someone who has little experience in photography.

By: lana

lana — Thu, 06 Aug 2009 14:49:18 +0000

where do u find the sensor size on the lens

By: Amanda

Amanda — Sun, 24 Aug 2008 04:00:49 +0000

Thanks a billion for this! I just got an SLR a couple weeks ago and this really helps me understand more of what’s what.
Your tips are amazing!