p.2 #3 · Fuji xf 500mm f5.6 or Nikon 800 f6.3 or EF 600mm F4
F8 vs f6.3 is 2/3 of a stop, but there is a bigger difference than that between the lenses.
A 600 F/8 with a 1.4x tc on it is 840 F11. You would need a 1.33x tc to turn a 600 F8 into an 800mm lens, which would be 800 F10.64. So the difference is more like 1 1/3 stops going from 600 / 8 to 800 6.3. The actual Fuji on your 600 / 8 is like 918mm F12.24 for a full frame.
The Canon 500 f4 and Nikon 800 f6.3 are basically the same lens profile at different focal lengths. If you toss a Fuji crop on a 500 F4 you'd end up with a 765mm ~F6 equivalent. So on a 500 / 4 I would expect that combo to compare fairly well to a Z8 + 800 F6.3.
500 F5.6 with a 1.53x crop = 765mm ~F8.5. (I think that picks up 1/3 of a stop from 600/8?)
600 F4 with APS-C = 918mm ~F6.12 (2 stops)
I believe the 500 / 4 - 800 / 6.3 are a bit more than 2/3 of a stop smaller than a 600 / 4.
Where you need to decide is what the focal length you want is. Either 500 choice would end up with a wider frame, but both will capture more light than your current configuration. You don't need to go Z8 if you go 500 / 4, provided it focuses properly. 600 / 4 is obviously the best, but it comes with all of it's own drawbacks.
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p.2 #4 · Fuji xf 500mm f5.6 or Nikon 800 f6.3 or EF 600mm F4
bman212121 wrote:
F8 vs f6.3 is 2/3 of a stop, but there is a bigger difference than that between the lenses.
A 600 F/8 with a 1.4x tc on it is 840 F11. You would need a 1.33x tc to turn a 600 F8 into an 800mm lens, which would be 800 F10.64. So the difference is more like 1 1/3 stops going from 600 / 8 to 800 6.3. The actual Fuji on your 600 / 8 is like 918mm F12.24 for a full frame.
The Canon 500 f4 and Nikon 800 f6.3 are basically the same lens profile at different focal lengths. If you toss a Fuji crop on a 500 F4 you'd end up with a 765mm ~F6 equivalent. So on a 500 / 4 I would expect that combo to compare fairly well to a Z8 + 800 F6.3.
500 F5.6 with a 1.53x crop = 765mm ~F8.5. (I think that picks up 1/3 of a stop from 600/8?)
600 F4 with APS-C = 918mm ~F6.12 (2 stops)
I believe the 500 / 4 - 800 / 6.3 are a bit more than 2/3 of a stop smaller than a 600 / 4.
Where you need to decide is what the focal length you want is. Either 500 choice would end up with a wider frame, but both will capture more light than your current configuration. You don't need to go Z8 if you go 500 / 4, provided it focuses properly. 600 / 4 is obviously the best, but it comes with all of it's own drawbacks....Show more →
You can simplify the math by noting what the size of the entrance pupil is for each lens. This is the hole that actually lets in the light. It is the actual focal length divided by the actual aperture of the lens.
So a 500 f/5.6 lens has an entrance pupil of 89mm, whereas a 500 f/4 lens has an entrance pupil of 125mm and a 600 f/4 has an entrance pupil of 150mm, a 600 f/6.3 has an entrance pupil of 95mm, a 600 f/8 has an entrance pupil of 75mm, and an 800 f/6.3 has an entrance pupil of 127mm.
Cropping (or using a smaller sensor) can get you more reach, but it won't change the entrance pupil of the lens. It is the entrance pupil that determines the depth of field you will see and the amount of light with which you have to work. When we multiply the focal length and aperture by a crop factor we really are calculating the focal length and aperture for a lens with the same entrance pupil but a different focal length.
Bigger entrance pupils let you have higher shutter speed and shallower depth of field but they also increase the diameter of a lens, so a bigger entrance pupil also means a bigger lens. Bigger entrance pupil lenses also tend to be higher in price.
When you select a lens as always, you need to think about focal length. How much reach do you want? You need to think about price. How much are you willing to pay? You need to think about size. How big of a lens am I willing to carry? But you also need to think about entrance pupil size. How much light am I going to need to get the shot in the conditions in which I am shooting? There are of course tradeoffs.
So returning to the OPs question, a 500 f/5.6 will have just a little less reach on an APS-C camera than an 800 f/6.3 on a FF 35mm camera, but the 500 has a notably smaller entrance pupil so won't perform as well when you do not need to stop down. It will limit your shutter speed. It will be smaller, however, and most likely cheaper. Stepping up to a 600 f/4 will get you even more light, (and 500 f/5.6 to 800 f/6.3 and 800 f/6.3 to 600 f/4 are about the same size step up in getting more light) but what comes with that is a once again larger lens that will cost quite a bit more.
Of course if we are talking about the EF 600 f/4, the price will be held down because it is an older lens which means that the AF performance will likely be affected and it will be even bigger than a more modern lens. So again tradeoffs are made, but just a different set of tradeoffs.
p.2 #5 · Fuji xf 500mm f5.6 or Nikon 800 f6.3 or EF 600mm F4
Besides the possibility of a faster lens, you need to consider two other things: focal length and autofocus performance.
The difference between 500mm and 800mm is significant. I'm often shooting small birds, so the 800mm PF is ideal, even hand-held. For large wildlife and outdoor sports, the zone is 400mm-500mm. If I had only one fixed lens for wildlife, I'd probably go for 600mm. Nikon's popular 160-600mm is cheaper and more versatile with a small sacrifice in image quality.
If you're shooting primarily wildlife, you also should consider autofocus performance. The Nikon Z8 or Canon R5 Mark II will significantly outperform any of the Fuji cameras for wildlife (and sports). I'm using both Fuji and Nikon mirrorless systems now, but the Fuji is reserved for street photography, landscapes, travel and backpacking.
p.2 #6 · Fuji xf 500mm f5.6 or Nikon 800 f6.3 or EF 600mm F4
OP, I'd just go Canon and call it a day if you can swing it An R5 + 600 f/4 III and 100-500 makes for an amazing, do-everything combo. Pricey, yes, but top-shelf.
If sticking with Fuji, the XF500 is getting you one more stop of light over your 150-600, and I don't think that would have improved your situation in Costa Rica, but if you aren't regularly shooting in those sorts of conditions, I wouldn't let it dissuade you because dark jungle/canopy is going to give even f/4 glass a challenge. Going with the XF500 is going to be the most economical choice vs. the Canon suggestion above, so if budget is a concern, this is where I'd land. By all accounts it looks like a stellar lens, and if I wasn't invested in Nikon for my birding it'd be a lens I'd be heavily favoring for use on my X-T5. I ran the Nikon D500/500PF for years in all sorts of conditions, and it performed admirably; I wish I had today's noise reduction back then, it would have been that much better! Plus, compared to your zoom, the prime gives you a much more sharp/clear starting point, so along with that extra stop of aperture you're going to see a big jump in retained detail after NR.
Curious to see where the OP ends up with this one!
An R5 + 600 f/4 III and 100-500 makes for an amazing, do-everything combo. Pricey, yes, but top-shelf.