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Osprey at Long Reef. EOS R5 with RF 100-500mm L Heavy crop, no extender |
Last month I posted a piece about cropping images from the R5 with RF 100-500mm L lens to simulate a longer focal length than 500mm. You can read about this here.
At the time I wondered if the RF 1.4x extender would give better results.
I could not find any definitive test online to answer this question so I bought an RF 1.4x extender and have been testing it over the last two days, with hundreds of shots of a variety of subjects still and moving.
I compared results obtained with the 1.4x extender to those obtained using a simple crop.
I experimented with various combinations of hand held, tripod, stabiliser on and off and stabiliser mode (on the side of the lens).
I also tried shooting full frame versus the in-camera 1.6x crop.
All this generated hundreds of files from which I have been able to derive a definite conclusion, which is:
The extender is worse than useless
Really ?
Yes. It is worse than useless because:
1. Real world results for image quality obtained with the extender are no better and on my tests are often slightly worse than those obtainable by simply cropping, with or without the 1.6x in-camera crop mode. This applies to hand held or tripod mounted use on still or moving subjects.
2. The extender is expensive and
3. Using it is a nuisance. The lens has to be zoomed out to 300mm before the extender can be fitted. The process of fitting the extender in the field involves manipulating camera body, extender and lens plus their associated caps. This raises the chance of dropping, damaging or getting dust, sand or dirt in one of those expensive pieces of equipment.
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Can you pick which one of these crops was made with the extender and which is a simple crop ? The one showing clearer detail in the Casuarina fronds is the simple crop. By the way the trees are about 750 meters from the camera and the fronds are about 4mm in diameter. Hand held. |
Discussion
Of relevance to this issue, two things have changed since the EF/DSLR era.
1. In previous times we had cameras with lower pixel count sensors. Heavy cropping produced images with very low pixel counts. So on these cameras an extender made sense.
But on the 45Mpx R5 you can crop hard and still have enough pixels to make a nice image.
With the in-camera 1.6x crop you still have 17.5 Mpx, enough for a sharp clear image with a good lens.
2. EF lenses were and still are very good.
But the RF 100-500mm L is super good, delivering a remarkable level of real world sharpness, contrast and resolution, particularly on distant and moving subjects. When an extender is mounted behind the lens some degradation of resolution and sharpness is inevitable. This is not the case with a crop.
One thing has not changed. Mounting a 1.4x extender reduces the effective lens aperture by one stop.
That is not a big deal but it may have a negative effect on image quality by requiring a higher ISO setting. It could also have a negative effect on autofocus speed and accuracy.
On my tests the extender definitely has an adverse effect on stabiliser effectiveness, with higher shutter speeds (and therefore higher ISO settings) being required for sharp results when the extender is mounted.
Conclusion
If you have Canon RF100-500mm L lens and are wondering if maybe you should get an extender, I strongly suggest not doing so.
If you are contemplating the purchase of an RF 100-500mm L lens for your RF mount Canon body, my advice is, go for it. That lens is really excellent and in my view worth the high price which Canon is asking and getting. Demand exceeds supply right now and I suspect that situation will continue for many months.
The best body currently available for the RF 100-500mm L lens is the EOS R5.