11-03-2021 08:36 PM - edited 11-04-2021 10:26 AM
Since some of Canon's RF lenses are slower than most typical EF lenses and I know it is said that that's not an issue since the mirrorless camera sensors are better able to handle higher ISOs but I have a question about that. Am I misinformed in thinking that when any camera auto-focuses, for a split second, the lens aperture is opened to the max to let in as much light as possible? If so, then what's different with mirrorless in that regard?
I'm asking this because my new RF 100-400 seems to struggle a little with gaining focus so I have to spend a little more time with a subject than when I use my EF 100-400 L ii. Or maybe I'm just spoiled by the "on point" AF capability of the EF. It's not really fair to compare those two lenses. And, I am very happy with the new lens--when it does zero in on my usually small subject like a bee, the picture is sharp (not like the L of course)--and it's just more work getting there. But due to its super light weight, I can carry it on long walks and not miss shots I normally would without it. I'm just curious about how the AF functions. I'm using an R5.
11-04-2021 10:15 AM
The camera initial focus is going to occur with the lens wide open. Even when a camera can still AF with a "slow" lens, the AF is going to be slower but this is somewhat offset by the less critical focusing with the smaller aperture glass due to the greater depth of field around the critical focus point.
From a cost and weight standpoint, there is a rationale for making these narrow aperture lenses and a big driver for mirrorless cameras is the reduced complexity and thus cost of manufacture so the two somewhat fit together.
Like Ernie stated, there are a lot of things a wide aperture lens can do that a narrow aperture cannot so it isn't just about focusing. The slowest lens I own are 400 and 800 f5.6 primes. I use the 400 f5.6 when hiking but it is a big step down in speed AND quality from the EF 400 f2.8 I use for sports. Outside of macro glass, I rarely have a lens stepped down to the f11 range and I would feel very limited with a telephoto of that type. I might change my mind when the fast glass starts feeling too heavy 🙂
Rodger
11-04-2021 10:36 AM
" I might change my mind when the fast glass starts feeling too heavy"
I use to carry two 1 Series camera bodies with big lenses all the time and not really think about it. Now I think I about it.
I am still not interested on a f11 or even a f8 lens. Had them in the past!
11-04-2021 10:56 AM
Despite what Canon has in its marketing material, I wouldn't consider the RF lens for sports/action or birds in flight. but I suspect that the difference in cost between $13K for the 800mm EF lens and $900 for the 800mm RF lens, coupled with the apparently very good IBIS for the mirrorless bodies would make that lens attractive to wildlife photographers. Many wildlife shots are basically still shots so fast shutter speed isn't essential.
11-04-2021 12:34 PM
11-04-2021 01:20 PM
I am using a B+W clear filter although probably don't need it since I have the hood--I just automatically put it on there. I should try shooting without it though--thanks for that suggestion. I thought there was a bit of a haze on the picture but I couldn't get totally perpendicular to the bug for even focusing so assumed that was the problem instead of the filter. Thanks.
11-04-2021 02:30 PM
03/26/2024: New firmware updates are available.
EOS 1DX Mark III - Version 1.9.0
12/05/2023: New firmware updates are available.
EOS R6 Mark II - Version 1.3.0
07/31/2023: New firmware updates are available.
Canon U.S.A Inc. All Rights Reserved. Reproduction in whole or part without permission is prohibited.