Camera Focus Problem?

[mcraige]

I read on some recent threads about cameras having a back focus issues, and thought it sounded like what I am seeing on my Sony a65v. I did some searches, read as much information as I could find, and did a few tests. I think I can confidently say my camera has a focus issue, but wanted to see if the kind folks here could verify or provide some additional information.

I did some tests using a chart, and some additional using a series of batteries. All tests were done with 3 lenses

• 18-55mm kit lens at 18mm, f3.5 and a distance of 1.8'
• Sigma 30mm, f1.4 at a distance of 3'
• Minolta 70-210mm at 70mm, f4.5, and a distance of 7'

For all pics, the camera was mounted on a tripod, and a remote shutter release was used.

My a65v has 15 focus points, and I used local focus points 1-5, from the diagram below:

FocusPoints by mcraigelliott, on Flickr

The first pic was taken using focus point 1, focusing on the center battery. It looks OK, but the battery to the left of it looks like it is better focused to me.

DSC00001 by mcraigelliott, on Flickr

The second pic was taken using focus point 2, focusing on the battery to the left of center.

DSC00002 by mcraigelliott, on Flickr

The third pic was taken using focus point 3, focusing on the battery to the right of center.

DSC00003 by mcraigelliott, on Flickr

The fourth pic was taken using focus point 4, focusing on the left-most battery.

DSC00004 by mcraigelliott, on Flickr

And finally, the fifth pic was taken using focus point 5, focusing on the right-most battery.

DSC00005 by mcraigelliott, on Flickr

These were from the 18-55mm, but the others are similar. In all cases, using focus point 4 and the left-most battery, the pics were very blurry, or the camera was unable to focus.

So... do I have a problem with my camera? Are my tests invalid, and I should be trying something else? Any help would be greatly appreciated.

 

[Daisy14'sDH]

Can you do a micro adjustment with your camera? Looks like it is backfocusing a bit...

 

[bob100]

I read on some recent threads about cameras having a back focus issues, and thought it sounded like what I am seeing on my Sony a65v. I did some searches, read as much information as I could find, and did a few tests. I think I can confidently say my camera has a focus issue, but wanted to see if the kind folks here could verify or provide some additional information.

I did some tests using a chart, and some additional using a series of batteries. All tests were done with 3 lenses

• 18-55mm kit lens at 18mm, f3.5 and a distance of 1.8'
• Sigma 30mm, f1.4 at a distance of 3'
• Minolta 70-210mm at 70mm, f4.5, and a distance of 7'

For all pics, the camera was mounted on a tripod, and a remote shutter release was used.

My a65v has 15 focus points, and I used local focus points 1-5, from the diagram below:


The first pic was taken using focus point 1, focusing on the center battery. It looks OK, but the battery to the left of it looks like it is better focused to me.

The second pic was taken using focus point 2, focusing on the battery to the left of center.


The third pic was taken using focus point 3, focusing on the battery to the right of center.


The fourth pic was taken using focus point 4, focusing on the left-most battery.


And finally, the fifth pic was taken using focus point 5, focusing on the right-most battery.


These were from the 18-55mm, but the others are similar. In all cases, using focus point 4 and the left-most battery, the pics were very blurry, or the camera was unable to focus.

So... do I have a problem with my camera? Are my tests invalid, and I should be trying something else? Any help would be greatly appreciated.

hard to tell, the pics look underexposed, low shutter speed and at least one is obviously mis-focused. When I tested the Sigma 30mm 1.4 years ago the batteries were much closer together

one thing is certain: your sensor needs cleaning !!

Canon Rebel XSi - Sigma 30mm 1.4 @ f1.4 ISO 1600

 

[mcraige]

Can you do a micro adjustment with your camera? Looks like it is backfocusing a bit...

Unfortunately, I cannot do a micro-adjustment on the a65.

 

[photo_chick]

Try redoing your test with better light and see what you get. You're trying to focus on something that doesn't have a ton of contrast in less than ideal light, neither of which are helping your AF system perform.

 

[havoc315]

The off center focus points on most cameras (well, certainly on the Sony SLTs) are not as accurate as the center point. You really want to use the center point to judge back/front focus.
I would repeat the test with better light. Also, don't use the wide angle of the lens. On the kit, test it at 55mm, not 18mm. You want to test the lens with the narrowest possible DOF. Especially since slight back focus isn't going to be relevant in the real world at 18mm. At 18mm, even with a 3.5 aperture.. if you are 6 feet from your subject, you would get a DOF of nearly 6 feet, giving you a really wide margin of error. Similarly, test your Minolta telephoto lens at 210mm.
I know on the A55, there is a do-it-yourself way to adjust back focus if it's consistent across all lenses -- has to do with removing the cap by the flash and adjusting the placement of the AF module by adjusting some screws. Not sure if you can do it yourself on the A65.

If you are finding consistent significant back focus across all your lenses, and you are still under warranty, you can probably send the camera back to Sony and let them adjust it.

The issue is that focus is being measured by distance to the AF module, not to the actual imaging sensor. So if that AF module becomes ever so slightly displaced, then the distances don't line up perfectly, and you get back/front focus. You can also have slight back/front focus issues that are lens specific -- And the semi-pro cameras like the A77 allow micro adjustment per lens.
When I did my micro-adjustments, I did them outdoors so I could use 300mm of zoom, from quite a distance, in good light.
It does indeed look like you have back focusing. And also looks like you have a massive speck of dirty on the sensor!

 

[mcraige]

Thanks for all of the feedback so far. I'll increase lighting and re-do the test at the tests at 55mm and see what they look like.

one thing is certain: your sensor needs cleaning !!

Is this comment based on the spec in the upper-right of the picture, or is there something else? I think that is actually scratch on the table surface, and not a speck on the sensor, since it is in a different place on the pics taken with the 30mm and at 70mm. If it was on the sensor, it should be in the same location on every pic, correct? I visually looked at the sensor, and can't see anything on it, tho there is dust on the mirror (which I will clean).

 

[wiigirl]

Try redoing your test with better light and see what you get. You're trying to focus on something that doesn't have a ton of contrast in less than ideal light, neither of which are helping your AF system perform.

 

[SkaGoat]

If it's got similar results for all your lenses, I'd find out how much it'd cost to send it into Sony to have them calibrate it. If it was happening on one lens, but not the others it'd be a problem with the lens, but all the lens around the same amount of back focus is a camera problem.

IMO at least with my Canon 7D, the light you had, from a tri-pod with a remote trigger, that should have been more than enough light to nail focus.... but that's my 7D, not sure how it's Auto-Focus is compared to the Sony.