Eos 1 and Sigma 24-70 EX compatibility problem??

[terence_tong1]

i've just purchased both the eos 1 and the sigma used however i've found the

following problem with AF in low light very apparent.

 

in my study, at night, with just the desk lamp, i was trying to do some focusing

exercises but find the AF very sporatic and refuse to focus. unless i keep tapping the

shutter and can feel and hear the lens making small adjustment until it reach the

correct focus.

 

now if i tried to focus on a reflective surface, such as watches, vitamin bottles, it's at

90-95%, but say a dark color box which is about 5 feet away, it won't even try to

focus (you know, the lens go the full range back and forth)

 

Now i should note that the lens and body works fine during out door use in day

time...

 

i've tried the lens on a eos 5 and 630, no problem

i've tried 3 other stock Canon lens on the eos 1 body, no problem

 

what gives?

[nigel whitaker]

Terence,

 

I have an EOS 1n HS and use the Sigma 24-70 EX, and I think what you may be finding is a lack of contrast which is what the camera is looking for (remember the original EOS 1 is quite an old design by today's focussing standards). Prior to my 1n, I had EOS 5, and I think that the focussing on the 5 is possibly a little better than my 1n (and the EOS3 and 1v better still).

 

Things like watches and bottles with printed labels have edges and more contrast for the camera to focus on than many 'average room' items. You may find that the poor focus detection in low light is more noticeable at the wide end of the lens range?

 

I plan to upgrade my 1n some day, maybe to the 1v, mainly for the better focussing response, as I find some things (like aircraft against a bright sky) cause problems if they are not initially large enough in the frame for the camera to pick up on (and the focus hunts back and forth), by the time they are close enough (not long at 400mph), the camera too often misses the action.

 

You may find that attaching a speedlite helps as it has a focus assist pattern projector (there may be a way to turn the flash output off, and just use the IR beam projector).

[al_kaplan1]

It requires a certain amount of light to function and zoom lenses are slow. Switching to a faster prime lens might also help. If you shoot a lot in really low lighting conditions you need a manual rangefinder camera such as the Leica M series or one of the Bessa cameras which also use the Leica M lens mount. These can be focussed quite accurately in light too dim to comfortably read by! Autofocus, like auto exposure, is a compromise that works most of the time fairly well. It lacks what you have, a brain!

[terence_tong1]

is there a reason why the canon stock lens out perform the sigma in the AF aspect then?

the sigma is a "brighter" zoom @ 2.8

vs my 28-70 II 3.5-5.6

(i am not even comparing it to my 100 macro!)

 

how do you not flash but use the speedlite red LED?

[g.richardson]

Just a photo.net newbies 2 cents worth... ;-)

 

I had a similar problem with my EOS1 and a very early Tokina 28-70 2.8 lens a while back when I was shooting an awards ceremony in low light with the 540EZ's assist lamp. The lens would hunt for a bit then when it was near to finding focus make little twitching movements back and forth until it locked, whereas my canon 28-70 3.5-4.5 had no problems locking on first time. My best guess was the canon lens had a very light (and hence not much inertia) assembly which required moving for focussing compared to the tokina, which moved a 72mm diameter wedge of glass and metal (the whole front part of the lens and then some) on what felt like a ball bearing dampened gear train, which combined with the EOS1 + 540EZ combo's fairly quick focusing caused it to overshoot the focus point and then franticly try to get back to it? I suspect the slower and less accurate focus on the 630 would'nt have the same effect? As I say, just my theory...

 

Gary