Ophrys Photography

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Canon telephoto comparison

When taking pictures of wild animals or birds the photographer is frequently limited by how close he or she can get without alerting the subject and frightening it off. This distance is often known as the "circle of fear". At this fixed distance the photographer is effectively "focal length limited". Cameras with higher pixel density are beneficial under these circumstances as they have more pixels on target and enable greater cropping to increase image size. Clearly longer focal length lenses will be advantageous over shorter ones but are heavier and are usually more expensive to purchase.

Having recently acquired a 300mm f2.8 L IS lens I wanted to see if I could use this plus teleconverters as a substitute for the much heavier and bulkier 500mm f4 IS lens - particularly on longer treks or when travelling by plane.

As I also own the popular 100-400 f5.6 L IS and a 400mm f5.6 prime (non IS ) I was able to perform an interesting set of comparative tests. To give the lenses the best chance of performing near to their best, I stopped them all down to an aperture of f8.

Shooting details were as follows:
All images were taken at same 9 metre distance using Canon 1DmkIV camera,Gitzo tripod/Markins M10 ballhead, cable release, mirror lockup, all lenses and converters optimised with microadjustment All were taken at f8 and ISO 200 Av mode +0.33 exposure compensation. Image stabilisation turned off. Three images taken and the best of the three used. Images were processed in Photoshop CS5 from RAW. Images all lightly sharpened identically using USM (300%/0.3/0).

Starting uncropped image - fixed distance 9 metres



100% Crops

300mm f2.8 (300mm)
300mm + 1.4IIx converter (420mm)

400mm f5.6
500mm 54

100-400mm at 400mm (Nearer to 380mm)
300mm + 2x converter (600mm)

300mm + 1.4II x repeat
300mm image upsampled 1.4 times

Conclusions

These are all high-quality Canon L lenses and all put up a good performance considering how small the target butterfly was in the frame, as you can see from the starting image. At the 9m distance it comes as no surprise that the 500mm f4 produced the best image quality. The 300mm f2.8 image appears to be of similar quality but of course the image size is much smaller.

Next comes the 400mm f5.6 lens. Considering its budget price, it put in a very respectable performance when compared to the two heavyweight super-teles. It is limited by being a slow f5.6 lens and has no IS but its image quality is remarkable for the price.


Since carrying out lens micro-adjustments on the 100-400 f5.6 IS/1DmkIV combination I find it is performing much better than it did in the past when used on camera bodies where this was not possible. When stopped down to f8 it is performing well but is definitely less sharp and contrasty than the 400mm prime.When the lenses are used wide open at f5.6 the differences are even more marked (from previous experience). Although both lenses are supposedly 400mm there is an obvious size difference in their images - the 100-400mm actually provides more like 380mm at full extension.

There is clearly a drop off in image quality when the 1.4x converter is used on the 300mm f2.8L. The bare 500mm f4 is in another league and the 400mm f5.6 is at least as good from these tests. This came as a bit of a disappointment as I hoped that the expensive 300mm+converter combination would beat the budget 400mm prime. I had to reduce the size of the 420 mm converter image to a 400mm equivalent to determine that at this size there is actually little difference - otherwise the 400mm f5.6 actually won. Unfortunately the light changed a little between the two shots below but not sufficiently to negate the comparison.

400mm f5.6
300mm +1.4x converter (420mm) downsized to 400mm

 

It does offer a one-stop aperture benefit and has image stabilisation but does not focus as fast as the bare 400 prime.

I tried upsampling the bare 300mm image using Photoshop's "Bicubic smoother" so that the width of the image was increased by a factor of 1.4. This was inferior to using the 1.4x converter but perhaps not to the degree that one might expect.

Finally I tried the 300mm lens with the 2x converter. This produced a whopping focal length of 600mm. The resultant image was very large when viewed at 100% on the computer screen and the image quality was a little inferior to the 1.4x converter but not by much considering he huge size.

The use of extenders with the 300mm f2.8 lens do clearly degrade quality of this excellent lens but still produce very usable results - even when pixel-peeping at 100% as we are in this comparison.
I would not however consider the combinations to be serious competition to the bare 500mm f4 which (along with the 600mm f4 and 800mm f5.6) remain the first choice for bird photography. It must be said though that these tests were conducted using a cable release and mirror lockup which is not practicable to use in the field when photographing moving creatures. Under real-world conditions the photographer's long-lens technique will become very significant and the differences between the lenses will reduce.

There is no question that the 400mm f5.6 gives you the best bang for your buck in this test. It is quite a bargain when used within its constraints.

The bare 300mm f2.8 L IS lens remains one of Canon's very best lenses and has not been seen at its best in these tests. If the lens-to-subject distance had been reduced to match the size of the 500mm f4 image the image quality differences would be very similar and could even go the 300's way - but that is a test for another day !


Canon 300mm f2.8 on the Gitzo tripod with 500mm
f4 on the ground. Both are sporting Lenscote
camouflage protectors.

Part two


I wanted to further compare the 300mm f2.8 lens with and without converters against my 500mm f4 reference lens. This time instead of using a fixed distance I wanted to use identical framing (magnification) in each case. In other words, I had to place the tripod closer to the subject at the shorter focal lengths and move it further back for the longer lenses .I achieved this by framing a ruler identically in the viewfinder in each case, this was then subsequently removed for the shots.
I took shots at a variety of apertures but have presented those at f8 in the comparisons below.
My subject was my usual favourite model - Chimpy. He was sporting a feather hat which provided the focal point for the images. (marked in red). The camera was the 1DmkIV and I used ISO 800 as the light was poor.

Starting image framing:



100% Crops:

500mm f4 Control:


300mm f2.8 bare


300mm + 1.4x converter


300mm + 2x converter



Conclusions

All lenses and combinations put in an exceptional performance. When viewed at 100% there were no real surprises. The bare prime lenses put in pretty much identical performances and the 1.4x converter caused a very subtle loss of resolution - visible on the fur above Chimpy's eyes. The 2x converter caused a further reduction in resolution but was only visible in these huge 100% crops. I would not hesitate to use the 300mm f2.8 L with either converter but I would still use the 500mm f4 if I did not have to carry the lens far. When travelling by plane or on a longer hike I will be taking the 300mm plus extenders in future !

To finish, here is a shot of a nuthatch at 420mm - taken with the 300mm f2.8 plus 1.4x converter:and the 1DmkIV camera.