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Lens Magnification Question


Hello, I'm choosing between RF 100-400 and RF 100-500 L lenses. I am somewhat confused about something.

If I set both lenses to 400mm and take a photograph of a bird say at the same distance, the size of the bird on the final image files should be the same for both.

However, the specs say that the magnification factor for the 100-400 is greater (.41 vs .33). What relevance is this to the image I get out at the end? Is it purely what I see in the image finder when I take the photograph?



Maximum magnification is a result of both focal length and focus distance.

The RF 100-400 has a max magnification of .41x, but only at 400mm and at a focus distance of 34.65”.                      
The RF 100-500 has a max magnification of .33x, but only at 500mm and at a focus distance of 35.43”.

When both lenses are set to 400mm, and both lenses are at the same focus distance, the magnification should be roughly equal. Both in the viewfinder and in the final image.

In reality there will be some sight differences because not all stated focal lengths are exact, and there can be differences at different focus distances. (ie: focus breathing)


Mike Sowsun

View solution in original post



Thanks for the comments. Not sure I fully understand the bits about using the whole of the lens when only the centre circle is used on the image. Maybe its to do with the light capture.

However, I have taken the plunge and ordered the RF 100-500 L series lens. Yes it is very expensive - nearly £3000 here in the UK - $3600 equivalent. Don't know why we always seem to have to pay more here for electronic items - in this case $1000 more.

You have confirmed my suspicions about better results from a 1.6 camera when compared to cropping a full frame camera. No doubt some might disagree, but it will also depend on the number of pixels and camera quality. Maybe a really expensive full frame will give better results due to better light handling, focusing etc.

Anyway, thanks for the comments.

You won't be disappointed with the RF 100-500mm lens.

I guess you already have an R series camera, then? What did you go for? The R7? Or something else?

I have ranted in the past about the cost of Canon and other tech equipment in the UK compared to US prices. Our prices are quoted inclusive of VAT, of course, so the dealer is only keeping £2500 out of a £3000 purchase. In the USA, I understand, prices are quoted exclusive of sales tax, which varies from state to state. So our US friends pay generally a little more for their camera gear that the dollar price on the Canon website. However I think it's nothing like the 20% that we pay. So if you do the maths, the prices we are paying are still considerably higher than in the US, even after you strip off the tax element. Canon have explained, I seem to remember, that this is justified by higher distribution costs in Europe than across the pond. 🤔

R6mkII, various lenses, speedlites. Also legacy Canons going back to T90 and even A1.

Thanks for the comments.

Don't have an R series camera yet, but am going for the R7. Maybe at a future date I will get a really good full frame camera and do my own comparison. Not at the moment though.