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APS-C question

bigbrother
Enthusiast

So if you see my last 2-page thread on portrait lenses, I got a big education on AOV, sensor size, etc.

I was used to shooting with my 50mm on an M50 and a good amount of cropping; the AOV did not look like a human eye’s.

So I understood everything about cropping, etc. But, I’m sitting at my brother’s house right now; he’s got a 70D with an 18-135 lens and a nifty fifty. Knowing what I thought I knew, I expected the 18-135, set at 50, to be cropped like mine. Well, it wasn’t. At 50, the AOV looked identical to my eye. I slapped on the nifty to confirm and yep, identical to the eye. Makes no sense to me given it’s an APS-C sensor and everything I learned.

The *only* confounding variable here is that, don’t laugh, we can’t find his SD card and so I’m only using the viewfinder. Is it that the viewfinder is optically akin to a full frame, and if the LCD were on and we were seeing the sensor’s image, it would be cropped as expected?

Thanks all!!!

2 REPLIES 2

MikeSowsun
Authority
Authority

@bigbrother wrote:


The *only* confounding variable here is that, don’t laugh, we can’t find his SD card and so I’m only using the viewfinder. Is it that the viewfinder is optically akin to a full frame, and if the LCD were on and we were seeing the sensor’s image, it would be cropped as expected?

Thanks all!!!


Yes, the viewfinders on different cameras have different coverages and different magnification. The viewfinder specs on the 70D are 98% coverage and .95x magnification.  Right now you could view the image on the 70D without an SDcard, if you use the rear LCD in LiveView. If you did, it would look the same as your M50. 

EF4AF7B9-EB97-422A-952B-661EA63B1601.jpeg

Mike Sowsun

ebiggs1
Legend
Legend

I don't totally understand what you are seeing. Remember a 50mm lens mounted on any crop sensor size camera will produce the exact same photo.  However, looking at viewfinders there can be a slight misrepresentation of that photo.  Also, slight tolerance in manufacturing will also lead to slight discrepancies. I don't know the "exact" FL of the Canon 50mm f1.8 lens but I will guess it is not exactly 50mm.  Just as your brothers 18-135mm isn't exactly those numbers either.  Matter of fact I will guarantee you they aren't. Possibly you didn't get the zoom lens set to exactly 50mm either.

 

You need to compare the resulting photos.  Keep in mind a lens is a lens is a lens.  It can not change any of it parameters after it is made.  No matter what camera it is mounted on a 50mm will always be a 50mm and so on and so on. The AOV is what is affected.

EB
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