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04/11/2005 01:21:22 AM · #1 |
Is it possbile to use two lens extenders... for example one 2x extender and one 1.4x with a Canon 70-200mm? if yes do you lose a lot of quality on it?
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04/11/2005 01:28:21 AM · #2 |
Canon's AF will quite working when the lens (or lens and TC compbo) hits f5.6. So since a 2x will cost you 2 stops and a 1.4X 1 stop, you lose 2 stops total. If you start with a 2.8 lens you might be OK. You can of course focus manaully.
This is from a canon lens brochure:
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04/11/2005 07:07:34 PM · #3 |
If what you're asking is whether it will WORK, the auto-aperture control will be transmitted on any modern extenders regardless of how many you daisychain together. Canon autofocus will only work on a final aperture of f/5.6 as prof_fate explained, but this means that just a single extender pushes a lot of telephotos over this limit anyway so it's no big deal.
However, as for the quality you lose... it's exponential. Not only will each extender add its own optical flaws, it will also double the optical flaws of everything in front of it. If your lens has a little chromatic aberration, a 2x extender will make that twice more obvious - and a second one would make it four times more obvious, which may often enough to ruin an image on its own. Moreover you'll have to deal with losing 4 stops of light in such a setup, which would make a tripod necessary for all but the very brightest conditions.
To get good quality teleconverters, such as canon's L ones, costs an absolute fortune and even they still lose you SOME quality - in the end it may be better to buy a longer lens for the same amount of money as you'd spend on a pair of really good teleconverters and your short lens.
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04/11/2005 07:55:33 PM · #4 |
Originally posted by Discraft:
Is it possbile to use two lens extenders... for example one 2x extender and one 1.4x with a Canon 70-200mm? if yes do you lose a lot of quality on it? |
The EF 70-200mm f/2.8 is so good and bright enough that I have no reservations using it with an EF 2x (a two-stop aperture loss on a bright day is perfectly acceptable). The f/4 version of the same lens is, obviously, two stops slower with the same extender, which, already, impairs its application, unless the light is absolutely cooperative. Otherwise, the image quality appears quite good with the 2x mounted.
To use both extenders on either versions of this lens, IMO, is not practical. Even if you used a tripod, a remote and mirror-lock, I'd expect to end up with such a limited number of decent, usable shots, I wouln't consider it. But...
to have both extenders and use them, each respectively, yes, this is practical. I, too, have pondered of how to, economically, extend this zoom for wildlife/birding and such uses. The EF 100-400 is not bright enough and does not autofocus with a 1.4x even to warrant the expense. The EF 300 mm f/2.8 (heavy) is our best bet here with a cost of about US $ 4.000. The optics of this lens are absolutely stunning, too.
What I am saying, in a nutshell, is that in order to get beyond an effective 448/640 mm (crop factor and all) with a decent image quality, you need $ 4000 (plus tax).
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04/12/2005 10:10:03 PM · #5 |
Originally posted by zeuszen:
Originally posted by Discraft:
Is it possbile to use two lens extenders... for example one 2x extender and one 1.4x with a Canon 70-200mm? if yes do you lose a lot of quality on it? |
The EF 70-200mm f/2.8 is so good and bright enough that I have no reservations using it with an EF 2x (a two-stop aperture loss on a bright day is perfectly acceptable). The f/4 version of the same lens is, obviously, two stops slower with the same extender, which, already, impairs its application, unless the light is absolutely cooperative. Otherwise, the image quality appears quite good with the 2x mounted.
To use both extenders on either versions of this lens, IMO, is not practical. Even if you used a tripod, a remote and mirror-lock, I'd expect to end up with such a limited number of decent, usable shots, I wouln't consider it. But...
to have both extenders and use them, each respectively, yes, this is practical. I, too, have pondered of how to, economically, extend this zoom for wildlife/birding and such uses. The EF 100-400 is not bright enough and does not autofocus with a 1.4x even to warrant the expense. The EF 300 mm f/2.8 (heavy) is our best bet here with a cost of about US $ 4.000. The optics of this lens are absolutely stunning, too.
What I am saying, in a nutshell, is that in order to get beyond an effective 448/640 mm (crop factor and all) with a decent image quality, you need $ 4000 (plus tax). |
That's a very naive conclusion to draw. Check ebay to find canon L glass even up to 1200mm going regularly for only a couple thousand pounds, or four or so thousand of your mickey mouse dollars :)
Moreover, you're saying the 70-200 is "so good and bright" so you want to ruin its quality by sticking a cheap doubler in front of it? Makes sense... even a dirt-cheap 100-400 would outperform that unless you're using a canon L extender in the mid triple figures.
And as for not getting good results even when using mirror lock, etc... that's nonsense. At worst the overall effective aperture would be f/8 with that lens and two extenders - i regularly handhold much longer lenses at f/11 with good results! Anyway, things like mirror lockup on tripods are only of any use in live action photography when you're using REALLY physically big lenses, as they resonate with the vibration of the shutter - a piddly 200mm with a couple of extenders on it won't have the weight or the length to be seriously affected by mirror vibration.
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04/12/2005 11:19:40 PM · #6 |
> riot
To counter an alleged naïveté with a flippant response is not much better, IMHO.
Last time I checked, a Canon 1200 mm L went for well over a $ US 100.000. If you can find me one in good condition for US $ 4.000, I buy it.
And no, I did not recommend to "stick a cheap doubler" in front of an Canon EF 70-200 f/2.8. I did refer instead to Canon Extender EF, which denotes 'L' glass, even though even Canon does not label it so.
Neither did or do I seriously suggest that mirror lock-up is a requirement for using more than one extender on a single lens. The listing of various common means to achieve ultimate image quality was a hyperbolic phrase. To say it country-simple: Even if you use every conceivable means and take every precaution to ensure the highest image quality, doubling extenders in front of the lens puts so much glass between subject and sensor, that the chances of landing decent shots, consistently and reliably, would be reduced beyond my tolerance.
I also know a number of photographers who use both remote and mirror lock-up, pedantically, with stationary subjects. I am one only of them. But then again, there are different aims and ambitions, neither one of which should exclude another.
Considering the tone of your post, I do sincerely hope, that you will act less flippantly at thirty than I am, allegedly, naive at age fifty.
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04/12/2005 11:31:14 PM · #7 |
Originally posted by riot:
That's a very naive conclusion to draw. Check ebay to find canon L glass even up to 1200mm going regularly for only a couple thousand pounds, or four or so thousand of your mickey mouse dollars :)
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Bullshit! You would be hard pressed to find even a 600/4L in descent shape for $4,000US, eBay or anywhere.
Message edited by author 2005-04-12 23:40:55.
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