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Old Oct 19, 2005, 12:41 PM   #1
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:?Hi... I'm new here and I own a Minolta Maxxum 7D... purchased in March of this year. I was using the kit lenses from my Maxxum 5 which I broke about a month earlier than I purchased the 7D. I wanted a better lens with greater aperture. Went through 3 different used lenses and returned all of them assuming they weren't functioning properly on the camera (focusing issues). Finally just purchased a totally new Minolta AF 85mm, f/1.4 G (D) lens... but I'm still having focusing problems. I've read about the back focus problems in the thread below and I'm assuming that might be my problem because I never noticed anything until I began to use the lenses with the larger apertures at closer distances. The strange thing is mine seems to occasionally back focus and at other times it front focuses. At this point, I think it's only on AF. I'm doing further testing to make sure. My question: If it's truly a problem with the camera, does it only show up on AF or is it obvious on MF also? I just want to make sure this is a problem that CAN be corrected before I return it to Minolta. There seems to be a higher number of Minolta users here than where I normally visit, so I thought I'd ask here.

BTW, it's not a DOF issue in and of itself because there will often be quite a large area in focus... but it's just not the area I was aiming for.
I've also checked the Focus Area Switch. I currently have it on the wide focus area, but previously had it on the center square of the 9 focus areas... but it did it there also.
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Old Oct 19, 2005, 3:56 PM   #2
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What position is the focus selctor in?

The one on the front of the camera. You have S, A, C and M.



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Old Oct 19, 2005, 7:10 PM   #3
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I currently have it set on the (S) Single-shot AF, but I haveoccasionally used the(C)Continuous AF depending on what I'm shooting.I currentlyhave my AF/MF toggle switch set to where I can toggle between the two.
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Old Oct 20, 2005, 11:02 AM   #4
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If you're shooting wide open, DOF is going to be *very* shallow at closer ranges.

So, if you're not sure you're selecting the center focus point (or whatever point you selected for your subject), it's very easy for it to be off (ditto if you lean just a *little* bit after getting AF lock at wider apertures)

I've got a Tamron 35-105mm f/2.8 that looked like it could be having a BF problem shooting wide open (some shots I took yesterday afternoon looked that way).

But, I think what'shappening is that the lens is actually softer in the center versus just outside of centerat some focal lengths, based on MTF charts I see for it, and it's not *that* sharp shooting wide open. Remind me to stick with sharperprimes shooting wide open in low light. :-)

Here's a very crude test I just did. I arranged some books on a table, focusing on the one with the white top andorange bottom (the one the text is sharpest on in the middle of the image), using the Maxxum 5D. I kept light relatively low on purpose.

You can probably do a lot better with something else.Since the Minolta100mm f/2 is the sharpest lens I've got shooting wide open, I decided to use it to recheck the camera's AF. I had previously checked it quickly with a 50mm f/1.7, too. It's just fine. I shot it at ISO 800 and f/2.8 indoors (although the camera is going to focus wide open at f/2).

The Tamron was acting a bit strange with the AF tests, though. Again, I'm thinking it's just that lens shooting wide open in low light (strange looking MTF Charts).

The 85mm f/1.4 isn't that sharp wide open either, judging by the MTF charts at http://www.photodo.com (it looks like it would need to be stopped down to somewhere between f/2 and f/2.8 to match the 100mm f/2 shooting wide open).

But, it does look at lot more consistent across the frame compared to something like the Tamron zoom I was using yesterday.

But, you may want to check the camera out real good using the sharpest lens you've got wide open, since the camera is going to be focusing wide open regardless of your selected aperture (and think of a better test than this one if possible). LOL I've been told that KM uses the 50mm f/1.7 to calibrate them with if you need to send it in.

This was taken from approx. 6 feet away, where depth of field in front of and behind your focus point is less than1 inch at this aperture and focal length

http://www.pbase.com/jcockfield/image/51015183


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Old Oct 20, 2005, 11:26 AM   #5
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Thanks Jim. I'm still doing some testing. I think this has been so difficult for me to determine because of various issues at different times. For instance, I mentioned ordering 3 different used lenses and returning all of them. Well, I'm 100% certain that two of them were actually faulty lenses and would not focus properly on the camera... but I'm beginning to think the second one just needed some fine tuning on my part. When I had the last lens, I had the cameraset to the center square focus area... but nothing worked properly and it wasn't a DOF issue.WhenIhad it onMF, and the focus lightcame on to let me know it was focused... it wasn't anywhere near focused. Andit wouldn'tautofocus at all half the time.I know older lenses focus slower on this camera, but this one was EXTREME. The guy at the camera shop where I purchased the camera recommended I use the wide focus area instead of the center focus area at that time so I've left it there until this morning. Someone on another website said the wide focus frame allows the camera more choice of what it wants to focus on which was not what I understood from the camera shop. Anyway, I switched it back to the center focus and with this new lens, it seemed to work well so far. I'll see what happens with further testing.
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Old Oct 20, 2005, 12:01 PM   #6
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The first night I was out with the 5D, I was having a lot of fun shooting wide open at ISO 1600 with a 28mm f/2 at shutter speeds as slow as 1/10 - 1/15 second in a dimly lit restaurant.

I thought "cool" when I looked at the images. No sign of motion blur from camera shake (even though shutter speeds that slow are"taxing" both my ability to squeeze the shutter button smoothly and the cameras's Antishake design I'm sure).

It would have been even better if my subjects were in focus, but what I did focus onwas sharp enough. :-)

I switched to Center Only AF after that first night.I think it was probably just me (I don't like these "new fangled" mutipointAF systems).

DOF is pretty darn shallow at wider apertures and closer ranges, too (don't lean any after locking focus). :-)

Then, I shot with the Tamron 35-105mm f/2.8 yesterday wide open in very low light (at pretty darn slow shutter speeds hand held, too), and italso seemed to have a bit of a problem with AF accuracy. But, testing it more today, I don't think it's the camera.

I think it's just this particular lens shooting wide open (and judging from MTF charts, it's softer in the center compared to just outside at some focal lengths, which may give the appearance of BF sometimes, too). I also suspect that's fooling the AF sometimes (although perhaps it's just got acompatibility issue of some kind, since it is an older lens).

Darn it... my eyes are getting too bad to use MF in low light, and I got the KM DSLRmodel with the smaller viewfinder. LOL

I mighttest the Tamron 35-105mm f/2.8 a little more today. But, the camera's AFseems to be "spot on" using a sharper Minolta prime at wider apertures, based on my crude tests.


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Old Oct 20, 2005, 12:19 PM   #7
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gracie328 wrote:
Quote:
I think this has been so difficult for me to determine because of various issues at different times. For instance, I mentioned ordering 3 different used lenses and returning all of them. Well, I'm 100% certain that two of them were actually faulty lenses and would not focus properly on the camera... but I'm beginning to think the second one just needed some fine tuning on my part.
What lenses were they out of curiousity?
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Old Oct 20, 2005, 1:03 PM   #8
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The first was a Sigma lens... can't recall exactly (70-210, I think)... but I know it wasnot an EX model. The second was another Sigma with similar zoom, but it was an EX model. I did get several good pics with it, but everything was usually very soft... and it did appear to have some actual focus issues occasionally too... although it's been a while and I'm not sure what I had the Focus Area set on at that time. It was recommended by several people that I stay away from Sigma, and the customer service rep at KEH (where I purchased them) even admitted to several problems with Sigma lenses working properly on the new DSLRs. So, I exchanged it for a used Minolta 100mm, f/2.8 macro lens. It was as bad as the first Sigma if not worse. The camera froze up with it once or twice... it made a grinding noise when attempting to focus. AF was totally useless on it... and MF wasn't too hot as I mentioned above it sometimes wouldn't even properlymanually focus... the focus light would be on as though it was focused, but I could even see with my eye through the viewfinder that it wasn't and it would be sharper if I focused it on my own without relying on the focus light. That's when I decided to purchase the brand new Minolta 85mm, f/1.4. I realize the DOF is extremely limited at f/1.4.... don't think I've even opened it that wide yet. I think f/2 is about as far as I've gone. But several of my pics would have quite a large area in focus... but it just wasn't what I wanted in focus, so I knew it wasn't a DOF thing. Here's a good example: Notice the leaves are in focus, but the actual rose isn't. I did use a tripod. I was gettingLOTS of this type.

http://img.photobucket.com/albums/v3...CT0047copy.jpg

It did seem to do better this morning when I switched it back to the center spot. Here's an example from this morning. I intentionally chose this composition to give the camera the opportunity to 'be confused' and focus on the wrong thing... but it did focus on the center of the flower.

http://img.photobucket.com/albums/v3...CT0033copy.jpg

And one more from this morning... where I focused on the bud in front instead of the flower center. It did well.

http://img.photobucket.com/albums/v3...CT0036copy.jpg

Hopefully, this will continue.
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Old Oct 20, 2005, 1:25 PM   #9
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gracie328 wrote:
Quote:
The first was a Sigma lens... can't recall exactly (70-210, I think)... but I know it wasnot an EX model. The second was another Sigma with similar zoom, but it was an EX model. I
A common problem with some of the older Sigmas is that they may need rechipping for newer Minolta cameras.

There is a place in Georgia that does them now.I talked to them yesterday asking them questions about it, since I noticed that Sigma added this vendor as a new Service Center here (I'm in Georgia). They tell me it runs around $25.00 - $45.00 per lens, and takes around a week to 10 days to turn them around.

It would probably be a good idea to check with Sigma on each lens you may consider, just to make sure they can rechip it (I understand that they can rechip most of them to work properly).

As for KEH. Yep... They're a super place to shop for used equipment (and they are usually pretty conservative with their ratings, too).

Quote:
So, I exchanged it for a used Minolta 100mm, f/2.8 macro lens. It was as bad as the first Sigma if not worse. The camera froze up with it once or twice... it made a grinding noise when attempting to focus. AF was totally useless on it... and MF wasn't too hot as I mentioned above it sometimes wouldn't even properlymanually focus... the focus light would be on as though it was focused, but I could even see with my eye through the viewfinder that it wasn't and it would be sharper if I focused it on my own without relying on the focus light.
[/quote]

Now, that is odd. That's supposed to be a very nice lens, and I wouldn't expect any compatibility problems from a Minolta lens.Maybe it had some kind of a problem from being dropped or something (with the grinding noises, it sounds like it).

I've got a Sigma (Nikon mount) that makes grinding noises now, too. But, I'll forgive it, as it's an old and well used lens (I think the gears are just worn slap out in it). It's aSigma 35-70mm f/3.5-4.5 "Zoom Master" AF lens, that's probably just about worthless, even if it wasn't making grinding noises. Laugh if you want, but this lens has always been one of my favorites.

Quote:
That's when I decided to purchase the brand new Minolta 85mm, f/1.4. I realize the DOF is extremely limited at f/1.4.... don't think I've even opened it that wide yet. I think f/2 is about as far as I've gone. But several of my pics would have quite a large area in focus... but it just wasn't what I wanted in focus, so I knew it wasn't a DOF thing. Here's a good example: Notice the leaves are in focus, but the actual rose isn't. I did use a tripod. I was gettingLOTS of this type.

http://img.photobucket.com/albums/v3...CT0047copy.jpg
That one front focused. If I had to guess, the wrong focus point was selected. It probablygrabbed the one closest to the camera, and if you're not watching it closely, you may miss it (I think the default is something like 3/10 of a second, but you can make it a little longer). If I were shooting sports, I may like these newer AF systems. But, I think I'll stick to center point only and reframe. LOL


Quote:
And one more from this morning... where I focused on the bud in front instead of the flower center. It did well.

http://img.photobucket.com/albums/v3...CT0036copy.jpg
Yes, that worked very nicely!



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Old Oct 20, 2005, 6:07 PM   #10
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Jim this little BS about charge Sigma lenses.I spoke with Sigma custom AND THEY SAID ITS free ONLY 10$ SID

Call to Sigma custom to NY and they Fixed lenses free

Stars.

I spoke with CHRIS in AR ,same price

and tech clear told me what free send to Sigma
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