I started exactly the same discussion in a German forum and the comments were quite interesting. Suddenly, a few Sony shooters were: "well, F8 at 800mm is a necessity and the obvious choice" to "F8? no thanks" to "What Sony does is a NEED, but Canon deliberately forces unnecessary high f-numbers" on everybody
Yes, and f/7.1 is f/7.1. But somehow (to some people) f/6.3 was just peachy while f/7.1 was 'unusably dark', meaning the RF 100-500 was 'horrible' to say nothing of the RF 200-800. The point is that story will change once Sony launches a zoom lens with an f/8 in the maximum aperture...now, f/8 will be just peachy (because it's 800mm, so of course it can't be f/6.3, right?), and f/9 will be the new 'unusably dark'.
I regularly use both the 100-500 and 200-800 and am perfectly OK with going on a couple of mile walks with the 200-800 over my shoulder. And I am one of the oldest members here, nursing a new knee. The 200-800 is at the maximum weight for me, though, for hand holding. The 100-500mm + 1.4xTC, according to TDP, weighs 1834g with tripod foot and hood, only 300g less than the 200-800mm with foot and hood.
It was a very subjective statement/ opinion of mine.
Fair enough. I am an opportunistic photographer and need the camera to be at the ready as I walk along and spot something. So, I carry it on a BlackRapid strap with two caribiners, one attached to the tripod foot and another to the base of the body. I've done that for many years, with heavier lenses like the EF 400mm f/4 II with extenders and have got used to it. Actually, with the heavier lens as I got older I went over to a BlackRapid double breathe using its two carabiners in the same way so the camera was across my front, and the weight supported over both shoulders.
1. The size of the Airy disk, the measure of the limits of resolution caused by diffraction, depends only on the f-number of the lens and is independent of focal length, and so an 800mm lens is no more affected by diffraction than an 8mm lens of the same f-number (radius of disk = 1.22 x f-number x wavelength of light).
www.canonrumors.com
1. The size of the Airy disk, the measure of the limits of resolution caused by diffraction, depends only on the f-number of the lens and is independent of focal length, and so an 800mm lens is no more affected by diffraction than an 8mm lens of the same f-number (radius of disk = 1.22 x f-number x wavelength of light).
2. As the effects of diffraction scale linearly with f-number, even if f/8 were fully diffraction limited for resolution, an increase to f/9 would at the most lower resolution by 12.5%, which would not be very noticeable, if at all.
I posted a thread about diffraction some 6 years ago.
Diffraction, Airy Disks and implications
I am interested in the basic physics of optics, and it provides useful information on choice of equipment and settings. Diffraction plays an important part in image quality, and its importance is becoming increasingly relevant as high density sensors are becoming more widely used. So, I thought...
The drop off in sharpness is due mainly to lens aberration, not diffraction. The resolution of the RF 200-800mm peaks at about. 650mm (found by me and others in the CR forum), where the aperture is already f/9 and remains about constant until 800mm f/9. At a constant aperture of f/9, the resolution should increase linearly with focal length. So, it should increase by 23% from 650mm to 800mm, but it remains nearly flat. Here is the evidence if you want to follow it up.
www.canonrumors.com
If you want to make price/quality comparisons, the RF 200-800mm at $1799 is very nearly as sharp in the centre as is the RF 800mm f/5.6 costing nearly 10x as much at $1699. The 200-800mm performs quite nicely at 800mm. Here is a centre crop of an image I took this week (1px of it = 1 px of original) processed from RAW with no added sharpening. I would not describe it as very far from ideal, but you might.
It will be interesting to see what the filter size is. The Canon 200-800 objective is the full diameter of a 95mm filter and f/8 calculates to 100mm, so without going to a 105mm filter, they will be overstating the f number and at 105mm, it will likely be heavier than the Canon. Physics is a hard mistress.
