Comparison of 300m refractor vs 500mm reflex: 500mm head crop

$Comparison of 300m refractor vs 500mm reflex: 500mm head crop$

It is often said that for wildlife, especially birds, you always want more reach. That's one of the reasons I have a 500mm reflex lens -- the Sony AF 500mm f8 lens. But this lens is often criticised for its softness, lack of contrast, and nasty bokeh, compared to a refractor lens. I also have the Tamron SP 70-300mm DI, said to be one of the better mid priced zooms in that range. I have been advised by some of those more expert in wildlife photography that the weaknesses of the 500mm reflex are bad enough that the Tamron should outperform it. Whereas I'm rather a fan of reflex, and suspect that some of its bad reputation is due to misunderstanding and misuse of this rather difficult lens.

So here's my first test of the hypothesis that my good 300mm should be better than my allegedly bad 500mm. The subject is a heron quietly perched in a high distant large bush. It's distant enough that these images are both cropped down quite a lot to fill the frame with the bird. In linear terms to Tamron is cropped down about to about 25% and the reflex to about 50%. The camera is a 24MP Sony A77, a crop sensor DSLT. In both cases the bird was in the centre of the frame. AF central spot focusing was used, the focus point being placed on the head. So this is a test of central image quality.

Both images were processed from RAW. I edited the Tamron image first, finding the settings which produced the best heron image. I used exactly the same settings for the 500mm image, which put it at a slight disadvantage, but makes the images more objectively comparable. Both images after processing and cropping have been downsized by 67% since that made little if any difference to the detail resolution.

This is the head crop from the 500mm reflex image upsized by 250% linearly, which makes it the same size as the 400% upsized 300mm image.

The superiority of the 500m image in detail resolution is dramatically obvious. There seems to be a large bit of extra white fluff near the tip of the underside of the beak in the 500mm image. The heron was at the time periodically doing a bit of oxter preening. He's in a slightly different position in each shot. My guess is that he did a bit of preening while I was changing the lens.

There's more contrast and colour in 300mm image, which I expected. The 500mm reflex always gives me flatter images which always need more post processing contrast and saturation boost to look like the images I get from my other lenses. Part of that difference may be due to the extra 2/3 stop exposure the 300mm shot got (if the light didn't change while I changed lenses). Both were shot at ISO 100 and 1/200th second with image stabilisation on, while the camera was supported on a monopod. The 300mm was taken at f6.3, 1/3 stop underexposed by the metering to help preserve pale feather detail. The 500mm shot was taken at f8, its only aperture. So the 500mm was slightly disadvantaged both by being given the same processing for the 300mm, and less exposure to keep the other parameters the same. By being technically slightly disadvantageous to the 500mm I hoped that would make any apparent superiority in the 500mm image more likely to be the result of a superiority in the lens itself.

Those are minor differences, however, compared to the obvious superiority in detail resolution of the 500mm.

Here is the 300mm head crop.

Here is the 300mm version of this full body image. (approx 25% linear crop of the ex-camera image).

Here is the 500mm full body crop (approx 50% linear crop of the ex-camera image).

Original: DSC05179RW-001X250

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Taken in: United Kingdom / Scotland / Edinburgh / Stockbridge (show map)

Taken on: April 2, 2015

Tags:

edinburgh

botanic

RBGE

500mm

reflex

bird

heron

head

crop

SAL-500F80 « less

Sets appears in: • Birds • Technical Comparisons

Groups appears in: • Herons and Egrets • Edinburgh Photographers more » • Birds and Wildlife UK • 500mm F8 reflex telephoto lens (Sony/Minolta) « less

Camera: Sony SLT-A77V, f/8.0, 1/200 sec, 500mm (=750mm), ISO 100 (more info) (hide info)

Camera:	Sony SLT-A77V
Aperture:	f/8.0
Exposure Time:	0.005 sec (1/200)
Focal Length:	500mm (35mm equivalent: 750mm)
ISO:	100
Exposure Bias:	0 EV
Flash:	Off, Did not fire
Exposure Program:	Manual
Exposure Mode:	Manual
Metering Mode:	Multi-segment
White Balance:	Auto
Contrast:	Low
Saturation:	Low
Sharpness:	Soft
Color Space:	sRGB
Software:	Image Data Converter
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$Comparison of 300m refractor vs 500mm reflex: 500mm head crop$

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