I don’t understand. The Canon 300D is absolutely fabulous above f/5.6.
it's true that there are focusing issues when slower than f/5.6. i don't think they have to do so much with the aperature, but with the connection between the camera and the teleconverter/lens.
Actually the issue isn't that you can't get great pictures above ƒ/5.6. The ability to decrease your aperture to ƒ/16 or ƒ/22 is definitely one of the benefits of a DSLR.
The issue is that when you are composing your shot, the lens is always "wide open" (at its maximum aperture -- smallest ƒ-number), to allow the viewfinder to be as bright as possible, which in turn gives the auto-focus sensors as much light as possible. Even if you are shooting the Canon 100mm/2.8 Macro at ƒ/22, while you are composing your shot, you are looking through the lens at ƒ/2.8. Only when you take the picture or press the DOF Preview button does the lens stop-down (very quickly!) to the actual aperture of ƒ/22 and then immediately open back up to ƒ/2.8.
The problem is that the AF sensors in Canon's "prosumer" DSLR's are only accurate down to the light level available at ƒ/5.6. So when your maximum aperture is reduced below that because of the lens (i.e., lower-cost zoom lenses that go to ƒ/6.3, adding a 2X teleconverter to an ƒ/4 lens, etc.), the AF sensors are now outside of their design limits and do not function accurately. In addition, the viewfinder physically gets darker and darker the "slower" the lens is. (To see how dark an ƒ/6.3 lens is, put on a "fast" lens like the 50mm/1.8, go to Av mode, dial in 6.3, and then compare the viewfinder brightness while pushing and releasing the DOF Preview button. It is a pretty big difference!)
When folks talk about "fast" and "slow" lenses, they aren't talking about the speed of their focusing. They are talking about the maximum aperture. A fast lens has small ƒ-numbers (the 50mm/1.8 is "fast".) A slow lens has large ƒ-numbers (a low-cost 75-300 zoom that goes from ƒ/3.5-5.6 would be "slow", especially at the telephoto end). Personally, I consider anything ƒ/2.8 or under to be "fast", but even 2.8 isn't enough in some indoor lighting situations...
nice job of explaining what i failed to communicate. you can get non-canon converters to "trick" the camera into thinking the aperture is the same as before, but the autofocus will still search some.
on a side note. would you always expect a faster lens like 1.8 or 2.8 to focus quicker considering the focusing mechanisms are built the same, and lighting conditions are equal. i.e. 70-200mm 2.8 vs. 4.
if there is more light being let in shouldn't the lens be able to pick up on contrasts quicker?
Funny how you don't see things in photos until they're pointed out, or at least I don't. Where can I get one of those "discerning" plug-ins for my eyesight? Makes me not want to submit anything else with my lowly 18-55mm kit lens. First it was a mega pixel battle, now it's a superior glass race (maybe it always was before someone else pipes up). Where does it end? Good thing everyones not pro, cause it could real nasty. LOL
Print bigger :)
Then look at the prints, notice the things that stand out as bad.
Then look at how they occur in the images at web sizes.
It certainly isn't such a big deal for web sized images and normally don't really bother me, but they are obvious if you look for it. This is a thread discussing lens quality so they merit mention - otherwise I'd just say 'good shot' and move on.
Funny how you don't see things in photos until they're pointed out, or at least I don't. Where can I get one of those "discerning" plug-ins for my eyesight? Makes me not want to submit anything else with my lowly 18-55mm kit lens. First it was a mega pixel battle, now it's a superior glass race (maybe it always was before someone else pipes up). Where does it end? Good thing everyones not pro, cause it could real nasty. LOL
Print bigger :)
Then look at the prints, notice the things that stand out as bad.
Then look at how they occur in the images at web sizes.
It certainly isn't such a big deal for web sized images and normally don't really bother me, but they are obvious if you look for it. This is a thread discussing lens quality so they merit mention - otherwise I'd just say 'good shot' and move on.
No doubt the difference in image quality is quite evident, even at web size, when the images are compared side by side.
you can have an unbelievable blast driving a VW GTI.
for another $30,000 you can get a Porsche. if you can afford it, you should probably get it, but if you can't, you shouldn't feel bad with the killer ride you got.
you can have an unbelievable blast driving a VW GTI.
for another $30,000 you can get a Porsche. if you can afford it, you should probably get it, but if you can't, you shouldn't feel bad with the killer ride you got.
; )
I hear ya man!! I was even considering the 75-300mm without IS.....talk about a tight wad.
This thread got a lot deeper than I expected, and I certainly appreciate all the input! I think I'll go with the 70-200 f/4L. I'll probably regret not having that extra 100mm sometimes, but what really struck me are the comments I've seen (here and on other sites) from 75-300 owners who got a 70-200 and were amazed at the difference. That says a lot more to me than numbers.
Shannon, have you bought yet? this thread was certainly an interesting read but I'm still not sure of the lens I should get to go with the 300D kit lens. I'm an beginner and doubt I'd see the difference twix a 300 and 200 ?
btw, looks to me like a Canon 28-105mm lens does a pretty fine job!
I bought the 70-200 f/4L. The 28-105 is a good lens, but the difference is readily apparent. I'll try to post some shots in a few hours.
Honestly, I probably would have been just as happy overall with the 75-300 (ignorance is bliss). I don't sell photos for a living, and my primary need was for reach, not stunning quality. The 75-300 lens gets soft at the long end, but I'd hazard a guess that a slightly soft 300mm shot isn't any worse than sharper 200mm shot enlarged to the same size. Just my two pence.
Well there's always the Sigma 100-300 F4 to confuse things further...
Originally posted by scalvert:
This thread got a lot deeper than I expected, and I certainly appreciate all the input! I think I'll go with the 70-200 f/4L. I'll probably regret not having that extra 100mm sometimes, but what really struck me are the comments I've seen (here and on other sites) from 75-300 owners who got a 70-200 and were amazed at the difference. That says a lot more to me than numbers.
I'd hazard a guess that a slightly soft 300mm shot isn't any worse than sharper 200mm shot enlarged to the same size...
Hm... My hunch is that the guy with the 200 mm will adapt to his equipment as much as the next guy with a 300 mm. He will likely get better at stalking and foot-zooming though than the 300 mm man. When he does, he won't have to enlarge anything and come off with the better image.
..and it gets more confusing. I have an annual trip on the Norfolk Broads, a boating holiday. Every year there is more and more wildlife to photograph. Should I pay an extra £200+ for a shorter lens? Am fast learning that moving to dSLR is going to play with my wallet :)
Here are two groups of images shot with the Canon 28-105mm and 70-200mm f/4L lenses. You be the judge. They're cropped, but otherwise untouched from the orginal. The deer and both goose photos are at full zoom, and all are handheld except for the soccer shot. The L glass is noticeably superior, but the other lens certainly wouldn't embarrass me.
