I don't get the focus issues..

J

jano

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I've read here and other places that sometimes people have trouble with the G1 or G2 autofocus when a lens is wide open, particularily the 90mm.

What on earth does the aperture have to do with focus on a rangefinder? I can understand an SLR.. but, again, focus relies on the rangefinder, NOT the lens. So I'm going to guess there's a different issue afoot.

Right?
 
The aperture controls depth of field and therefore the focus tolerance of the rangefinder system. Wide open, if the depth of field is 5mm at 1m object distance and the AF tolerance (how fine the focusing steps are) is greater than half that, then it is possible the focus can be off. Naturally, if you stop down, the AF system can take advantage the greater depth of field.

Then there is how well the AF system can detect the object distance. Depending on the qualities of the subject, depending if the AF system can "see" the object. Errors here can be hidden with greater depth of field.
 
In other words they program sloppiness into autofocus?

That's retarded.

I understand the second part, which basically has NOTHING to do directly with AF, just a subsequent result if the lens is misaligned, of the AF is not calibrated properly, then a low DOF will show you errors ON THE NEG/PRINT. However, in most all cases where I've read about this issue, people complain of it during camera operation, including such symptoms as focus hunt and and wrong distance.
 
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Yes, that's it exactly. You should write to the folks who used to run Contax/Kyocera and let them know that you've figured out what they did wrong with the AF on the G cameras: they should have programmed in less sloppiness.
 
There are tolerances in all mechanical equipment. You have to realize thoug that at a shallow DOF (wide open 90mm for example), at close range you could focus on a nose and have the ears out of focus.
 
Yes, I shall write them a scathing letter that will make them quiver in their pajamas at night.

I find it hard to believe that that's what they would do, and think there's a better explanation.

Note that I've not had any problems focusing wide open. I just read about it, and wondered about the validity.
 
Fastfashn said:
There are tolerances in all mechanical equipment. You have to realize thoug that at a shallow DOF (wide open 90mm for example), at close range you could focus on a nose and have the ears out of focus.
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I don't know if you know what I'm talking about... if you read up on the G2 and G1, you will into years back people complain about the focus problems when shooting wide open. I'm trying figure out HOW that occurs. Mechanical tolerances in your example would demonstrate a probem on the negative and print, not during use.
 
Jano, one thing with my G1 that gives me pause when I'm using it is that I find I can repeatedly focus on the same thing and the distance readout on the top deck of the camera sometimes shows different numbers. These can be as much as 10 cm different, if the readout is correct. So maybe what you're reading about is people getting apparent evidence of inconsistent focusing while they're using the camera, and if they are shooting wide open, then they will have the concern that the camera is missing focus. (Yes, you can do this same test with a manual focus camera too, but there you're looking at the distance scale on the lens, which will not give as precise a readout, and anyway you're relying on your own eyesight.) For what it's worth, I do think the G2's focusing system is improved over the G1's.
 
I read a lot of "mis focussing" on the G series cameras before I bought one back in, if memory serves me correctly, early to mid 2002.

I didn't get the whole "mis focus" issue myself.

I never had problems with focussing - I figured that 9/10 of the problems were with the end user not understanding HOW to properly use an AF camera - and that's still a big problem with most AF cameras.

People like to pick up their toys without reading the manuals and expect things to work without issue. It's only AFTER they run into problems do they refer back to the instruction manual :)

I'm a big proponent of RTFM first ... play with your toy.. and if you still have issues. THEN contact the manufacturer etc. :)

Cheers
Dave
 
I have not had any issues using the 90mm wide open, even at close range. Where I have read the most criticism is using the 90mm at its closest range and wide open. I think that the likely problem is that the photographer is standing too close to the subject where it is impossible for the camera to focus. This will of course result in the autofocusing hunting for the subject. In this type of situation, we're talking about attempting macro work with a rangefinder which is like hammering in a nail with a screwdriver. This is just one area where you should pick up your SLR if you aren't getting the results that you want from the rangefinder. It does seem silly to me that one would blame the camera for what I see as operator error. The easiest way to fix this problem is to take a step back and crop the negative when printing. Should work every time.
 
Konickon, good point. I have seen varying focus #'s as well.

Ariya, I agree, that does sound like a similar problem I've encountered.

Dave, I agree. There's an entire sub-manual dedicated to focusing with the G1 and G2 included with the camera (when new). I read that, and never really had a problem.. unless I was too close, or there wasn't any distinct, vertical line to focus on.
 
jano said:
In other words they program sloppiness into autofocus?

That's retarded.

I understand the second part, which basically has NOTHING to do directly with AF, just a subsequent result if the lens is misaligned, of the AF is not calibrated properly, then a low DOF will show you errors ON THE NEG/PRINT. However, in most all cases where I've read about this issue, people complain of it during camera operation, including such symptoms as focus hunt and and wrong distance.
Click to expand...


Not so much "Programmed in," as "mechanical reality." Not every lens is a perfect molecule-for-molecule duplicate so focal lengths differ slightly. Focusing cams also slightly differ. Camera bodies, &c. The DoF of a lens makes up for it- about 2cm at close focus on the 90mm, if I remember the chart in the back of the G2's manual.

After I got my last G2 fixed, the only thing I had to remember was to confirm focus in the little range-indicator in the viewfinder. If it had a wildly differing result from what I was expecting, I focused again, and all was well. Otherwise, no, the G2 never hunted- the lens found a position and STAYED THERE.
 
jano said:
Dave, I agree. There's an entire sub-manual dedicated to focusing with the G1 and G2 included with the camera (when new). I read that, and never really had a problem.. unless I was too close, or there wasn't any distinct, vertical line to focus on.
Click to expand...

Bingo.. that's it in a nutshell.

I always kept the distance in mind when focussing and the fact that a certain amount of "contrast" (whether that was a vertical line or a sharp white/black delineation) is required with ANY autofocus system.

The exact same problem can, and does, occur with the most advanced DSLR's nowadays too. In extreme low light, without any real contrast, you're going to get misfocus on shots... people expect camera techonology to be as good as the human eye/brain combination; and that just ain't the case.........yet :D

Cheers
Dave
 
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