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The Infamous 1.6x Factor


Hi All,

This is my first post to the Forum after it went to the new format.

Because I am interested in the new R7, I was watching the short video about it by Rudy Winston, Canon’s guy. It was disappointing to hear him repeat that confusing, and inaccurate, statement about how an APS-C sensor effectively gives you more telephoto magnification. To quote him, “With the APS-C sensor’s natural 1.6 times effective increase in a lens’s telephoto coverage, the EOS R7 squarely targets sports, wildlife, and especially bird photographers.” His use of “coverage” is nebulous, I admit. Is there another way to interpret that word?

As bird photographers know, what matters is how many pixels there are on the bird. Here are the published sensor widths and pixel info for the full-frame R5 and the R7:

R5     36mm/8192 pixels, or 227 pixels/mm

R7     22.3 mm/6160 pixels, or 276pixels/mm

For similarly cropped photos from these cameras, the R7 has 1.22x more pixels along the edges. When viewed on your monitor at 100% magnification, the R7’s photos would look 22% larger. For a cropped image of a bird or animal what really matters is how many pixels/mm the sensor has, and does not depend on its physical size.





The implied comparison is to a full frame camera with the same sensor megapixel rating. The more appropriate evaluation would be R7 vs R6. 

John Hoffman
Conway, NH

1D X Mark III, Many lenses, Pixma PRO-100, Pixma TR8620a, LR Classic


To me the whole thing is couched in often confusing terminology - I am not specifically referring to Rudy Wilson's  video here.  Very often the whole issue of that is captured is described in terms of focal length alone when this is clearly not the case - as per my colleagues' comments.
To me, this colloquial terminology that has not served the issue well and has produced a lot of debate and even angst around the issue.  To try to clarify this I have written my own document on the subject for my classes. 

While I accept that many people may not need to engage with this issue if they stick to one format and sensor size, the issues of matching sensors and lenses with different characteristics is giving it more prominence. 

So WFWIW, I offer the document HERE as my personal approach to the issue.

cheers, TREVOR

Professional photographer, engineer and educator since 1980

"All the beauty of life is made up of light and shadow", Leo Tolstoy;
"Skill in photography is acquired by practice and not by purchase" Percy W. Harris
"A good swordsman is more important than a good sword" Amit Kalantri
Technique will always Outlast Tech - Me

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