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Old Jun 26, 2005, 7:54 PM   #21
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Hi Jim,

You wrote: Comments on the 100-400mm f/4.5-6.7 lenses seem to indicate that they are sharp for the money except for some edge softeness, but tend to be a little softer above 300mm. Problems with Autofocus hunting at longer focal lengths have also been reported (to be expected with a slower lens).

I have the Tokina 100-400 and I too have problems with the autofocus at the 400 mark. If I back the zoom down a bit, it seems okay, but at the full 400, it grinds. I've already sent the lens back once, am I to assume that this is normal for this lens on my 7D? Should I send it back a second time or live with it?

FYI: It takes nice pictures, but thenI only use it to shoot soccer games, so most of the time I have pretty good light. I have better success manual focusing, as the autofocus seems to be too slow to capture the action, especially when the action is coming at you. Is this what you would expect for this lens too?

Thanks for the help.
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Old Jun 28, 2005, 10:11 PM   #22
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Got two MORE Sigma 18-50 3.5-5.6 lenses from B&H, both bad. That is FOUR of these I checked out, all form B&H - maybe they had a bad lot of them. Anyway, I also got a Vivitar Series 1 19-35 (used) from B&H and it is excellent. I would rather have the wider range, but quality comes first. Maybe a 18-50 from another seller would work, I don't know. Don't have time, as I leave Saturday for my month in the Canadian Rockies.

Also got a couple of TCs, a Kenko 1.5x and a Vivitar 2x. Kenko 1.5x works well, AF works with it so far. 2x from Vivitar does not work with AF. For the heck of it, I combined the two (3x!), but the results were blurry as one would imagine. Did NOT use tripod, so I expect better results when I do. Have not decided whether to keep the 1.5x or the 2x yet.
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Old Jun 30, 2005, 7:04 AM   #23
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Jacqueaux wrote:
Quote:
Got two MORE Sigma 18-50 3.5-5.6 lenses from B&H, both bad. That is FOUR of these I checked out, all form B&H - maybe they had a bad lot of them. Anyway, I also got a Vivitar Series 1 19-35 (used) from B&H and it is excellent. I would rather have the wider range, but quality comes first. Maybe a 18-50 from another seller would work, I don't know. Don't have time, as I leave Saturday for my month in the Canadian Rockies.
Well, I'm glad you got one wider lens (the Vivitar 19-35) that seems to work OK with it.

As for the Sigmas, I don't know what to tell you. I'd suspect the body calibration to be at fault (rather than 4 bad lenses). But, if you're still confident in the body, you may want to send a lens to Sigma to see if the lens is the problem if you go this route (Sigma 18-50).


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Old Jul 5, 2005, 9:37 AM   #24
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As an FYI, I found another wide zoomlens that may be worth considering.

It's the Tamron SP 20-40mm f/2.7-3.5 IF Aspherical.

It gets the highest rating of any wide zoom available in Minolta AF mount at photodo.com (Minolta, Tamron, Tokina, etc.), and it appears to be better "wide open" compared to the Minolta 20mm f/2.8 prime (and just asgood at wide open apertures compared to the Minolta 24mm f/2.8 prime, with a higher rating overall).

http://www.photodo.com/nav/prodindex.html

It's discontinued (and I have seen some comments about flare from some film users), buta 7D user I found with this lens says it's the sharpest wide zoom he's ever used on a 7D (and no backfocus problems).

I looked at somefull resolution images taken with this lens on a 7D at both wide open and stopped down apertures, and I'm impressed with what I see. He didn't have any samples shooting into the sun, though (and I am curious about flare). Color, sharpness, contrast looked fine to me.

I see this lensNIB from one Ebay vendor (probably clearing out old discontinuedstock) for$174.95. Used they're around $250-300 from most vendors, depending on condition (and tend to run closer to $600.00 when you can find one new).

When I saw the photodo.com ratings (combined witha $174.95 newprice from one Ebay vendor) Iordered one over the weekend-- *just in case* I decide to go witha KM DSLR in the future, so I'll have a relatively bright wide zoomlens that is actually usable atwide open apertures (and this one is still f/2.8 at 28mm, only stopping down tof/3.5 at 40mm).

Lens Purchase on Ebay

At this price (given the photodo.com ratings, which are based on unbiasedMTF tests versus opinion surveys), I figured I probably couldn't go wrong by buying one.

It would yielda 35mm equivalent focal range of around 30-60mm (after the 1.5x crop factor) on a 7D, allowingyou to stay within 1/2 stop of f/2.8 at all focal lengths -- which is about what I'd want if I went with a KM DSLR -- while still giving good results "wide open" (not taking flare, etc. into consideration).

If I don't go with a KM DSLR, I'll simply put it back on Ebay. ;-)


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