keith_bauer
Member
Will the 20D still autofocus using the 500 f/4 IS with the Canon 2x converter?
Thx
Thx
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2x converter on 500 f/4 with 20D
- Thread starter keith_bauer
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rdspear
Veteran Member
Doesn't two stops from f/4 take it to f/8, meaning only a 1-body at the central focus point will still autofocus?
I'm pretty sure the answer is no.
I'm pretty sure the answer is no.
I don't have a 500 f/4 so I'm not a 100% certain, but the 20D is capable of f4.0 > f/4.5 > f5.0 > f/5.6, thereby theoretically giving you three stops until you hit the AF barrier.
I think you have stops confused. When we talk about a 'stop', we are normally talking a 'Full stop'. Full stops are always a doubling or a halving of the amount of light.
Therefore: 1 stop from F4 is f5.6, or opening up is f2.8.
What you have done below is shown 1.3rd stops.
Full stops steps are f1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32 etc
A full 2 stops from f4 is f8 - so no, the 20D should not be able to autofocus (reliably anyway) at this aperture.
S.
SPy
--
(if there is one thing I have learnt on these forums - it's to think first and say exactly what you mean and write it in such a way that everyone can understand. And before posting - proof read it. Still working on it
~ Please excuse my English - I live in Australia. No offense mates ~
Therefore: 1 stop from F4 is f5.6, or opening up is f2.8.
What you have done below is shown 1.3rd stops.
Full stops steps are f1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32 etc
A full 2 stops from f4 is f8 - so no, the 20D should not be able to autofocus (reliably anyway) at this aperture.
S.
--
SPy
--
(if there is one thing I have learnt on these forums - it's to think first and say exactly what you mean and write it in such a way that everyone can understand. And before posting - proof read it. Still working on it
~ Please excuse my English - I live in Australia. No offense mates ~
krusadr
Veteran Member
You just got yourself a soft f8 lens.
Why? F8!
I don't understand why anyone would want to do that. Please tell me why.
'Silence! What is all this insolence? You will find yourself in gladiator school vewy quickly with wotten behaviour like that.'
Why? F8!
I don't understand why anyone would want to do that. Please tell me why.
--
'Silence! What is all this insolence? You will find yourself in gladiator school vewy quickly with wotten behaviour like that.'
jackkurtz
Veteran Member
The 20D needs f5.6 or faster as the maximum aperture for AF to work. That combo will give you f8.
Some third party converters might work because they do not accurately relay f-stop info to the body, but they are not usually as sharp as the Canon converters (and the af is nowhere near as accurate).
jack
--
A few of my photos:
http://www.sportsshooter.com/members.html?id=4177
Some third party converters might work because they do not accurately relay f-stop info to the body, but they are not usually as sharp as the Canon converters (and the af is nowhere near as accurate).
jack
--
A few of my photos:
http://www.sportsshooter.com/members.html?id=4177
Todd Walker
Veteran Member
Well of course this is just a guess, but I would say...to get a 1000mm lens? Just a thought of course.
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Todd Walker
http://www.toddwalker.net
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Colin K. Work
Veteran Member
I use that combination at times, and no it doesn't AF. However, manual focus is quite easy at long focal lengths as the subject very clearly pops in and out of focus.
The image quality obviously suffers a bit from the 2x, but if you stop down a stop or 2, good results are possible.
The real problem with shooting at this length is atmospheric conditions - haze (however generated) is a real problem, and you really need a crisp winter day to get the best results.
Cheers,
Colin
--
Colin K. Work
[email protected]
http://www.ckwphoto.com
The image quality obviously suffers a bit from the 2x, but if you stop down a stop or 2, good results are possible.
The real problem with shooting at this length is atmospheric conditions - haze (however generated) is a real problem, and you really need a crisp winter day to get the best results.
Cheers,
Colin
--
Colin K. Work
[email protected]
http://www.ckwphoto.com
krusadr
Veteran Member
What the heck would you want 1000mm f8 lens for? And don't say astro, it would suck so badly.
--
'Silence! What is all this insolence? You will find yourself in gladiator school vewy quickly with wotten behaviour like that.'
liquidstone
Forum Pro
... at shy Philippine birds.
From 300 feet, 350D + Sigmonster + Sigma 2x, 1600 mm
Liquidstone
http://www.pbase.com/liquidstone/top25
From 300 feet, 350D + Sigmonster + Sigma 2x, 1600 mm
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Liquidstone
http://www.pbase.com/liquidstone/top25
jahern
Leading Member
Used the Canon 500mm a few weeks ago with my 20D
It will focus with Canon 1.4x converter but not with the Canon 2x converter.
With the 1.4x it becomes a 700mm f/5.6, with the 2x it becomes a 1000mm f/8 (going with from the EXIF data in the RAW files).
Can't comment on any other converters as no expereince.
I found manual focus with the 20D difficult, but with the Canon Angle finder it was a lot easier.
John
It will focus with Canon 1.4x converter but not with the Canon 2x converter.
With the 1.4x it becomes a 700mm f/5.6, with the 2x it becomes a 1000mm f/8 (going with from the EXIF data in the RAW files).
Can't comment on any other converters as no expereince.
I found manual focus with the 20D difficult, but with the Canon Angle finder it was a lot easier.
John
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