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07-30-2015, 04:52 AM   #1
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50 mm crop factor

I understand the crop factor element on DSLRs, I use legacy film era lenses. Question is if I purchase a modern 50mm fixed does the crop factor apply or do I get a true 50?

07-30-2015, 05:21 AM   #2
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QuoteOriginally posted by Luddite Quote
I understand the crop factor element on DSLRs
Not sure that you do, actually, Luddite.

50mm is 50mm ... it's the focal length. This is true of your vintage K50 f1.2 or your modern DA50 f1.8.

Now ... the sensor may be cropped, giving your image a smaller Angle of View.
07-30-2015, 05:22 AM   #3
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The answer is no...50mm is 50mm old or new.
07-30-2015, 05:34 AM   #4
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if you use a 50mm lens on a aps-c sensor, you will be seeing the equivalent field of view of a 75mm lens on a full frame camera.

07-30-2015, 05:40 AM   #5
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I thought the crop factor was 1.6, making a 50mm actually a FOV 80mm on an APS-C sensor....
07-30-2015, 05:42 AM   #6
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I always heard it was 1.5x. Making a 50mm FOV 75mm.
07-30-2015, 05:49 AM   #7
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(shrugs)

6 over here and half-dozen over there, I suppose.... a quick Google search shows it depends upon what website you last read it on....

interesting...

---------- Post added 07-30-15 at 05:51 AM ----------

or is it because a Canon sensor is a smidge smaller?

I see the 1.6 factor seems to be associated with Canon sensors....
07-30-2015, 05:52 AM   #8
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QuoteOriginally posted by pepperberry farm Quote
I thought the crop factor was 1.6, making a 50mm actually a FOV 80mm on an APS-C sensor....
That's true on a Canon APS-C, but Nikon and Pentax have a slightly larger sensor making the crop factor 1.5x.

07-30-2015, 05:52 AM   #9
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I've read it here more than anywhere else so being a die hard Pentaxian, and we have many knowledgeable Pentaxians on here, I tend to believe their statements, more than anywhere else.
07-30-2015, 05:59 AM   #10
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I believe the Pentax and Nikon crop factor is 1.53. Canon is 1.60.
07-30-2015, 06:37 AM   #11
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Thanks for the replies gents. So to get 50mm would have to be 35mm to get near 50mm view which at 1.5 would be near 48mm.
07-30-2015, 06:54 AM   #12
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QuoteOriginally posted by Luddite Quote
I understand the crop factor element on DSLRs, I use legacy film era lenses. Question is if I purchase a modern 50mm fixed does the crop factor apply or do I get a true 50?
There have been many threads on this topic, so feel free to search for them.
That said, all 50mm lenses are 50mm, that is their lens property, and they project a certain angle of view, and a certain image circle diameter. How much of this image circle is captured depends on the size of the sensor, though. This is why the same 50mm lens on 645Z is wide angle, 50mm on FF in normal, 50mm on APSC is slightly tele, and 50mm on Q is telephoto. Because you see a smaller cutout (and this cutout has higher resolution, typically, since smaller sensors have higher pixel density). However, for a lens to make a big image circle, the lens itself has to be big, as well. This is why a lens made for FF is typically designed to project an image circle big enough for the FF film/sensor, but not big enough for 645 format. This is why you cannot use a Q lens on your APSC camera - the edges would be black, with just a small circle in the middle of the frame.

So, now you know. Focal length is a lens property, independent on camera. Angle of view, however, depends on both focal length and film/sensor size. You can use lenses from bigger formats on smaller formats, if you don't mind lugging around a huge lens. You usually get heavy vignetting if you use lenses from smaller formats. That said, many DA lenses are FF compatible - there is a thread with test photos, just search for DA lenses on full frame. Oh, and having a huge image circle is not necessarily great, either. It means more glass, which projects light onto nothing, so its useless, and the extra light can bounce around the mirror box and cause odd flares, loss of contrast,.. basically, the best is to have a lens with image circle just right for the camera's sensor.

If you buy older or bigger lenses, they will give the same field of view on your camera, as DA or APSC crop sensor lenses, if they have the same focal length
07-30-2015, 09:07 AM   #13
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QuoteOriginally posted by Luddite Quote
Thanks for the replies gents. So to get 50mm would have to be 35mm to get near 50mm view which at 1.5 would be near 48mm.
As an aside, the modern 35mm's are generally all amazing no matter what brand. I suspect its a relatively simple design to tackle, or the demand is simply there for them with the smaller sensors.
07-30-2015, 09:26 AM - 1 Like   #14
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The other advantage of old glass on new sensors is that the old glass was sometimes not the best at the edges. By losing that part of the field of view, you get the best of the old lens. On the other hand, this means there may be wailing with sackcloth and ashes when the FF DSLR comes out and the hitherto unseen flaws are revealed to those not conversant with film!
07-30-2015, 10:10 AM   #15
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QuoteOriginally posted by Imp Quote
if you use a 50mm lens on a aps-c sensor, you will be seeing the equivalent field of view of a 75mm lens on a full frame camera.
But only the FOV will correlate. The DOF and other imaging parameters will be that of a 50.

QuoteOriginally posted by pepperberry farm Quote
I thought the crop factor was 1.6, making a 50mm actually a FOV 80mm on an APS-C sensor....
Pentax has 1.5 crop factor. Only Canon has 1.6.

QuoteOriginally posted by Luddite Quote
Thanks for the replies gents. So to get 50mm would have to be 35mm to get near 50mm view which at 1.5 would be near 48mm.
A 35 will get you roughly the field of view (or angle of view) of a 50, yes. But that's all.The lens is still a 35, performing like a 35 would.
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