Minolta MAxxum 50mm 1.7 not focussing right on A77

[jfrabat]

Roaming around eBay, I found an item with the following description: Minolta AF maxxum lens 50mm f1.7 Lens in good clean shape auto focus SHARP. For $47, I figured, "What the heck" and ordered it. After receiving it, I have noticed that the Sony SLT-A77 will not focus right on it. I did not get to play too much with it, but what little I fooled around with, it seems it CAN get images into focus, but it will not do it automatically (what I mean is, I used the auto-focus, and I could not see the part of the picture I focused in focus, but other parts where), and the lens takes a LOOOOOOONG time to finish its auto-focusing process.

My questions are these:

1. Do you think this is something I can fix with the micro-adjustment of the focus in the camera?
2. Is it normal for this lens to take so long to focus? I plan to use it mostly as a portrait lens, but shouldn't a fast lens focus FASTER?

Felipe

 

[dxqcanada]

Are you stating that the Camera will not get image in focus automatically ... but you can get focus if you set to manual focus ?

 

[dxqcanada]

If you can get the center in focus and the surrounding circular area is way out of focus ... it sounds like someone took the lens completely apart and put in one of elements in reverse when reassembled.

* assuming that is even posssible

 

[jfrabat]

Unfortunately, I don't have my camera with me, but I set the lens to 1.7/f and shot a candle my wife has in the room to see the bokeh... Well, the front of the candle was out of focus (this is where the focus point was set to focus on), but the rear of the candle was in focus. I tried the same experiment with different distances and objects and lighting setups, but (IT SEEMS! I have to do more test to say for sure, as I could only take a few shots due to time!) always the lens was focusing BEHIND the area where it was SUPPOSED to focus...

If you had asked me, I would have said that the lens was taken apart and then put back together (no signs of this on the lens, but that is how it is behaving), and it was never calibrated (I know you need to place the lens in a machine to make sure everything is in working order and the difraction and all that is within guidelines).

 

[dxqcanada]

Hmm, back focus.

I don't know the A77, but I you should be able to do some adjustments.

 

[jfrabat]

I was reading online (some Flickr discussions), and it seems this is a relatively common problem when wide open (read about 3 cases online). I will have to play around with it when I get a chance, and see if I can fix it...

 

[jfrabat]

I fooled around with it a bit, and it seems to be getting there. What do you guys think? I tried having the focal point on different parts of the frame for each shot to compare; all are at 1.7/f, by the way...

_DSC1241 | Flickr - Photo Sharing!

_DSC1240 | Flickr - Photo Sharing!

_DSC1242 | Flickr - Photo Sharing!

The subject is a tiny replica of the World Cup I have on my desk, which means the texture is irregular for the sea and a bit polished for the continents.

Felipe

 

[dxqcanada]

Not sure, I still think something is up with that lens.

Here is a shot with my Maxxum 50mm f/1.7 shot wide open on my A57.
It has no problem with quick focusing. No hunting.
Not the sharpest thing wide open especially close up.

 

[DiskoJoe]

Not sure, I still think something is up with that lens.

I think its the owner.

Im wondering if he was far enough away for it to focus properly.

min. focus distance(mm): 450 = 17.7165 in

 

[jfrabat]

Not sure, I still think something is up with that lens.

I think its the owner.

Im wondering if he was far enough away for it to focus properly.

min. focus distance(mm): 450 = 17.7165 in

Actually, it was the auto focus adjustment... I did the AF Micro Adjustment on all my lenses, and the 70-300 was spot on, the 16-80 was a bit off (+2), but this lens was WAAAAY off (+13).