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The Cannon 100-500 RF lens, A review from a bird photography perspective

     


I’ve been using my new Cannon lens for approaching two months now and thought it would be useful to share my experience with birders who read my blog. Very unfairly, I will compare it to my other go to lens combination, my cannon 500mm with x2 converter and RF adaptor.

 

Ease of use

 

It would not be an exaggeration to say that my new zoom lens has revolutionised the way I birdwatch. This is a simple and obvious result of the relative weight and size. While the 500mm prime comes in at a hefty 3.2kg the zoom lens is more than 50% lighter at just 1.5Kg. It is also a third shorter. 

 

The large cumbersome 500 prime always limited how far it was comfortable to walk. Compared to this I hardly notice I’m carrying the zoom lens. This means I’m happy, for instance, wandering around the Wyre Forest for 7 hours. Something I would not contemplate with the 500mm prime where I would tend to stay in one or two spots.


    


 

Image Softness

 

As you would expect, the images with the zoom lens are noticeably softer than those shot with the prime. This is hardly surprising given that the prime is four times the cost and has much larger lens elements.

 

A prime is designed for maximum sharpness at its given focal length whereas sharpness on a zoom is always compromised by the averaging effect of maximising sharpness across a range of focal lengths.

 

Having said that, with appropriate post processing of RAW images using a gentle combination of Lightroom and Topaz software, the images are quite acceptable. I say gentle as I see many pictures processed by Topaz which are over sharpened leading to unusual artefacts in the final image.

 

Use with x1.4 extender

 

There is an oddity using the zoom lens with an extender. It limits the travel of the zoom lens such that the minimum focal length is much increased. I’m guessing this has been done to keep the overall size of the lens down but it is a very annoying feature and negates some of the advantage of a variable focal length when used for bird photography. When using the prime lens with x2 extender the small field of view at some x20 magnification can make it quite troublesome to find the bird, particular in more challenging habitat, for example a warbler in a hedge. The big advantage of the zoom  is that you can find the bird at smaller magnification and then zoom onto it. This is also particularly useful for fast moving birds in flight. With the extender on you can only zoom down to around 300mm somewhat negating this advantage.

 

Minimum aperture


At f8 this is one area where the prime plus 2x extender has a major advantage over the f10 zoom  at 500mm with x1.4. I like to shoot with the lens wide open where at all possible as this blurs any background distractions and leads the viewers eye to the subject. I suspect that the resulting reduction in light gathering capability will also be more noticeable in lower winter lighting which will push the iso number up at constant shutter speed. This will result in noisier images but again the excellent ability of the recently introduced noise reduction function in Lightroom will to some extent negate this.

 

Auto focus

 

I’ve found no noticeable difference in the excellent auto focus capability of both of these lenses. I have my R5 set up with eye detection on one of the back buttons, a feature I love and use regularly.

 

Focusing ring

 

The manual focusing ring on the zoom is tiny, much smaller than the prime lens even allowing for the proportional size reduction. In practice this can make it hard to locate a bird when looking through the view finder. Quite often with mobile birds you have a relatively short time for the autofocus to lock on before the bird moves so quickly locating the manual focus ring becomes very important.

 

General build quality

 

No issues here at all. The exceptional general build quality is what all users of the Cannon professional lens range have come to expect.

 

Summary

 

I would highly recommend the zoom lens for bird photography, especially when a lot of walking is involved. For hide photography, however, I will use the prime. Overall owning both the prime and zooms covers all bases and I’m exceptionally happy to have both in my armoury.

 

Footnote – my blogs are posted with sometimes rather imaginative spelling and grammar due to my extreme dyslexia!  

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