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Archive 2016 · Focal lengths and senor sizes

  
 
Michael White
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p.1 #1 · p.1 #1 · Focal lengths and senor sizes


Ok the old stand lense for 35mm was a 50mm.

So if I get things straight you would use a 50mm on a ff sensor to get the same field of view.
So on a 1.6x crop sensor a 35mm would be the closest to the same field of view.

Is that correct?



Aug 19, 2016 at 12:10 PM
JimmyJames
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p.1 #2 · p.1 #2 · Focal lengths and senor sizes


Yes, pretty much. The 40mm STM is a close compromise.



Aug 19, 2016 at 12:23 PM
garyvot
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p.1 #3 · p.1 #3 · Focal lengths and senor sizes


Yes. Because of Canon's slightly smaller 1.6x sensor, 35 gives the equivalent field of view of a 56mm lens on full frame.

You can do the math, but:

28 = ~45mm
24 = ~38mm



Aug 19, 2016 at 12:35 PM
dhphoto
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p.1 #4 · p.1 #4 · Focal lengths and senor sizes


JimmyJames wrote:
Yes, pretty much. The 40mm STM is a close compromise.


Not really.

An eqiuvalent field of view on an APS-C sensor would be 31.25mm, so more roughly, a 30mm lens. It's one of the reasons the Canon 28mm f1.8 is more popular these days as of course is the Sigma 30mm

40mm is too long (it's equivalent to* 64mm on full frame)


*= has an approximately equivalent angle of view to



Aug 19, 2016 at 01:45 PM
notherenow
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p.1 #5 · p.1 #5 · Focal lengths and senor sizes


Some quick shots to show.

Using a Sony FF camera but with a Canon 18-55 IS ii kit lens.

FF 50mm, APSC 50mm and APSC 35mm. Sony APSC is 1.5x crop rather than 1.6 and 35mm APSC is a bit narrower angle of view than 50mm FF (IE a bit more "reach").
The lens reads as a Sony A mount SAM in EXIF but is the Canon APSC IS ii kit lens.

Edited on Apr 15, 2017 at 03:19 PM · View previous versions



Aug 19, 2016 at 06:19 PM
Michael White
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p.1 #6 · p.1 #6 · Focal lengths and senor sizes


Another question regarding the efs lenses as I have one I think.

I think I have a 17-55 f2.8is lens

If I set it to 50mm will the field of view be the same as an ef-50mm lens on a 7d2? Or will it be closer to a ef28 on the 7d2?

I guess my question is really does the efs lens adjust for the smaller sensor or do it match the same field of view as an equaling sixe ef lens and there are other reasons you can't use them on ff cameras?



Aug 28, 2016 at 06:07 AM
melcat
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p.1 #7 · p.1 #7 · Focal lengths and senor sizes


Michael White wrote:
I think I have a 17-55 f2.8is lens. If I set it to 50mm will the field of view be the same as an ef-50mm lens on a 7d2?


Yes. 50mm is a length (2 inches, in fact), not an angle. It's the focal length, and it is independent of the sensor size.

Where your EF-S lens differs is:

1. The image it makes is smaller than an EF lens would - it doesn't cover a full frame sensor.
2. The bayonet is deliberately designed not to mount on a full frame camera. This is because some EF-S lenses would foul the mirror.




Aug 28, 2016 at 06:50 AM
jcolwell
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p.1 #8 · p.1 #8 · Focal lengths and senor sizes


Here's an example of how sensor size affects the captured image, for a constant focal length and constant subject distance...

"Basic question on exif and focal length", https://www.fredmiranda.com/forum/topic/1259833/0#11994647

...and here's a more detailed example discussing DOF with same and diffrent subject distances, but still showing the same "crop factor" effect.

"17-55/2.8 vs 24-70/2.8 Depth of field", https://www.fredmiranda.com/forum/topic/1420805/0#13479277



Aug 28, 2016 at 06:57 AM
gdanmitchell
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p.1 #9 · p.1 #9 · Focal lengths and senor sizes


Yup.

Just divide the full frame focal length by the crop factor (e.g. 50/1.6) to determine the focal length producing the same angle of view on crop. 31mm on 1.6x crop is approximately equivalent in angle-of-view terms to 50mm on full frame or 35mm film cameras.

Dan

Michael White wrote:
Ok the old stand lense for 35mm was a 50mm.

So if I get things straight you would use a 50mm on a ff sensor to get the same field of view.
So on a 1.6x crop sensor a 35mm would be the closest to the same field of view.

Is that correct?


Edited on Aug 28, 2016 at 10:33 AM · View previous versions



Aug 28, 2016 at 08:11 AM
Iwas joeking
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p.1 #10 · p.1 #10 · Focal lengths and senor sizes


Michael White wrote:
Another question regarding the efs lenses as I have one I think.

I think I have a 17-55 f2.8is lens

If I set it to 50mm will the field of view be the same as an ef-50mm lens on a 7d2? Or will it be closer to a ef28 on the 7d2?

I guess my question is really does the efs lens adjust for the smaller sensor or do it match the same field of view as an equaling sixe ef lens and there are other reasons you can't use them on ff cameras?


50mm is 50mm regardless of whether it's a prime or a zoom, HOWEVER, many zooms do not behave the same as a prime at a given focal length. By this I mean that it may say 50mm but it may, in fact, give the field of view of a shorter lens depending on your focus distance. Some lenses, have a drastically different effective focal length when focussed close. A couple of "famous" lenses showing this behavior were some models of Nikon's 70-200 and their old 70-180mm Macro.
The only reason I mention it is that you may make a comparison at some point and wonder what gives!



Aug 28, 2016 at 09:33 AM





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