topic Re: If 35mm on a full frame is normal . Would a 20mm on a crop be normal ? U know 35mm ÷ 1.6= 21 ? in EF & RF Lenses

If 35mm on a full frame is normal . Would a 20mm on a crop be normal ? U know 35mm ÷ 1.6= 21 ?

JJR70D — Wed, 15 Apr 2015 02:37:39 GMT

70d

Re: If 35mm on a full frame is normal . Would a 20mm on a crop be normal ? U know 35mm ÷ 1.6= 21 ?

cicopo — Wed, 15 Apr 2015 03:09:15 GMT

NO. 50 mm is considered Normal on full frame & you MULTIPLY, not divide when talking crop bodies so 30 mm X 1.6 =48 mm effectively.

Re: If 35mm on a full frame is normal . Would a 20mm on a crop be normal ? U know 35mm ÷ 1.6= 21 ?

ScottyP — Wed, 15 Apr 2015 09:56:49 GMT

So the lensest closest to a 50mm equivalent on Canon crop notices would be 30mm (rare) or 35mm (common).

Or you can dial it in on a zoom lens at 30 or 31 or whatever. It isn't really a critical thing.

A lot of people doubt the accuracy of the claim that 50mm on a full frame really equals the field of view of human vision, which is arguably wider. But that is what camera makers have called it so the name has stuck.

Re: If 35mm on a full frame is normal . Would a 20mm on a crop be normal ? U know 35mm ÷ 1.6= 21 ?

RobertTheFat — Wed, 15 Apr 2015 11:38:03 GMT

@cicopo wrote:
NO. 50 mm is considered Normal on full frame & you MULTIPLY, not divide when talking crop bodies so 30 mm X 1.6 =48 mm effectively.

No, there was nothing wrong with the OP's math; division is the correct operation for the direction his computation was going. It was only his underlying assumption (that 35mm is "normal" on a FF camera) that was wrong. IOW, 50 / 1.6 = 31.25, which is "normal" on a crop camera.

Re: If 35mm on a full frame is normal . Would a 20mm on a crop be normal ? U know 35mm ÷ 1.6= 21 ?

cicopo — Wed, 15 Apr 2015 12:51:40 GMT

Bob you are correct. I misinterpreted the way the question was being asked.

Re: If 35mm on a full frame is normal . Would a 20mm on a crop be normal ? U know 35mm ÷ 1.6= 21 ?

ebiggs1 — Wed, 15 Apr 2015 15:14:44 GMT

But to the OP's actual question, the answer is, yes. If he considers a 35mm lens "normal" than 20mm will appear the same normal.

Now we can debate whether 35mm is considered normal on a full frame or not. The image diagonal for FF is 43mm. Is that normal? APS-C is 30mm. Is that normal?

My personal taste is a 28mm on a crop and 50mm on a FF. But I may not be "normal" ?

Re: If 35mm on a full frame is normal . Would a 20mm on a crop be normal ? U know 35mm ÷ 1.6= 21 ?

amfoto1 — Wed, 15 Apr 2015 18:57:08 GMT

What's been considered a "normal" or "standard" lens has varied quite a bit over the years.... from 40mm to 58 or even 60mm on a film/full frame camera.

IMO, on a crop camera a 24mm or 28mm can serve nicely as a slightly wide "normal". 30mm on crop comes the closest to the standard 50mm on full frame. But 35mm is pretty close, and 40mm is only slightly telephoto. So, pick what you like best: 24mm to 40mm range. Any of them might work.

Then all you have to do is decide how you feel about "normal". When I was shooting film, I always prefered something a little wider.... so I generally used a 35mm or 40mm as my "normal". Now using some crop cameras, Canon EF 28/1.8 USM is my "normal" lens. (The 24/1.4L would be closer to my preferred angle of view and is 2/3 stop faster. But it's also a lot bigger, heavier and more expensive.)

If you are actually looking for a moderate wide angle like 35mm on full frame, then a 20 or 21mm would serve nicely. I use the EF 20/2.8 USM and like it alot on my crop sensor cameras. It's a bit bigger than the 28/1.8, though. And 1-1/3 stop "slower".

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Re: If 35mm on a full frame is normal . Would a 20mm on a crop be normal ? U know 35mm ÷ 1.6= 21 ?

TCampbell — Fri, 17 Apr 2015 04:54:57 GMT

There's a few accepted norms of what's "normal". For a 35mm film SLR (or "full frame" DSLR) a 50mm lens is considered a "normal" angle of view. For an APS-C camera it's about 30mm. For a medium format camera (Rollei, Hasselblad, PhaseOne, etc.) it's about 80mm.

But there's a slightly more accurate math-based way to calculate "normal". The "normals" provided above are rounded values to the next highest even multiple of 10.

For any camera sensor, if you calculate the diagonal measure of the sensor (in millimeters) then that is the focal length of the lens that is considered "normal".

For a 35mm film camera (or "full frame" DSLR) the sensor measures approximately 36mm wide by 24mm tall. That works out to about 43mm. √(24^2 + 36^2)

For an APS-C DSLR, it's roughly 23mm x 15mm. That works out to just over 27mm.

For a medium format 6x6 camera (6cm x 6cm) it's 85mm.

For a medium format 645 camera (6cm x 4.5cm) it's 75mm.

An image shot at a "normal" focal length will seem neither telephoto nor wide-angle. If you perform the "angle of view" calculation with such a lens, you end up with a horizontal angle of view of roughly 45º -- which somewhat approximates about what the human eye can take in without having to "look around".

Re: If 35mm on a full frame is normal . Would a 20mm on a crop be normal ? U know 35mm ÷ 1.6= 21 ?

RobertTheFat — Fri, 17 Apr 2015 12:02:36 GMT

@TCampbell wrote:
There's a few accepted norms of what's "normal". For a 35mm film SLR (or "full frame" DSLR) a 50mm lens is considered a "normal" angle of view. For an APS-C camera it's about 30mm. For a medium format camera (Rollei, Hasselblad, PhaseOne, etc.) it's about 80mm.

The usual lens on a 2¼ x 2¼ in. twin-lens reflex was 75 mm. I guess that had to be considered "normal" by definition, since very few TLRs had interchangeable lenses.

But there's a slightly more accurate math-based way to calculate "normal". The "normals" provided above are rounded values to the next highest even multiple of 10.

For any camera sensor, if you calculate the diagonal measure of the sensor (in millimeters) then that is the focal length of the lens that is considered "normal".

For a 35mm film camera (or "full frame" DSLR) the sensor measures approximately 36mm wide by 24mm tall. That works out to about 43mm. √(24^2 + 36^2)

For an APS-C DSLR, it's roughly 23mm x 15mm. That works out to just over 27mm.

For a medium format 6x6 camera (6cm x 6cm) it's 85mm.

For a medium format 645 camera (6cm x 4.5cm) it's 75mm.

But there's an obvious problem with using the diagonal to define "normal": It depends on the aspect ratio, which varies from format to format, from time period to time period, and sometimes from camera to camera. The highly touted "four thirds" format took its name from its (by that time) unusual aspect ratio, IIRC.

An image shot at a "normal" focal length will seem neither telephoto nor wide-angle. If you perform the "angle of view" calculation with such a lens, you end up with a horizontal angle of view of roughly 45º -- which somewhat approximates about what the human eye can take in without having to "look around".

At least using the angle of view of hte human eye makes more sense than using the diagonal, as long as it's confined to one dimension - presumably the horizontal, since that's where most peripheral vision lies.

Re: If 35mm on a full frame is normal . Would a 20mm on a crop be normal ? U know 35mm ÷ 1.6= 21 ?

JJR70D — Fri, 17 Apr 2015 15:39:03 GMT

Thanks all for your expertise. ...