Bother with back focussing

[bakubo]

Perhaps it's coming ....

http://www.flickr.com/groups/sony_alpha ... 820527326/

There is new update at the bottom of that page that says that this v5 fw has slots for 5 lenses and may get released in March plus some other changes. Of course, none of this may be true, but it might.

[Jonathan K]

Hi all,

since we are talking focussing issues again (and a potential solution to them):
The many posts here have made me believe that a lot of the 50/1.4 focus issues are (at least partly) due to focus shift. Since I use the Sigma 50/1.4, I also experience that in practice and it seems as if my A700 body is not that badly calibrated after all...

except:

The only other lens that does not work is the Macro 100/2.8. For macro photography it works, focussing seems fine (I didn't do any real "testing", just judging the results I get when use it), but between 4 an 7 meters distance the focus is way off... about 20-25 cm.

I own the second version of the Minolta 100/2.8 Macro. Is there any reason why this could be? Why should it be the only lens that does not work? Beercan or 100-300APO work fine at 100mm.
Since the center AF sensor is sensitive up to f2.8, there should be no reason for focus errors...

Does anybody else experience this?

Thanks in advance,

Jonathan

[lock]

Also worth mentioning is that with my 70-300G, the focus accuracy seems better towards 300mm. The telezoom samples posted previously were all at 70mm. Any advice is most welcome on how I go about getting my telezoom focus @ 70mm to work properly.

My 70200g shows a similar behaviour. Strong BF at 70 mm, more or less normal around 135 mm, but a tendency to FF at 200 mm. Get this V5 going !

lock

[stroberaver]

Woooh, that firmware would be superb. Would save me having to send off my camera & lenses, which I'm not at all looking forward to.

I had a look on sony's site for support information about sending my camera back whilst I'm waiting for a chance (i.e. daylight) to take those wide angle shots with the centre sensor - nngh, what a nightmare. Going round in circles, useless stating-the-obvious advice - anything but a simple email or phone number for UK service of Sony Alphas! Does anyone know if they have regional centres, or is it one place for the UK? The only option I can find is to submit a "service request" which seems to entail entering more information than buying car insurance! Anyone know where I can find some simple contact information of service centre(s)?

Try Photoclubalpha!

http://www.photoclubalpha.com/useful-an ... formation/" onclick="window.open(this.href);return false;

We also publish this and other links in every single magazine issue, along with an independent service shop for older gear.

David

D'oh! I'm a subscriber, too - forgot about the page of useful links and numbers inside each front cover. Thanks for the number.

I just wish Sony would say something about these v5 rumours. I need my camera for some kids birthday parties and events at my camera club, but I also want it to focus accurately!

[Brad Smith]

Hi strobeweaver,

My A300 back focused with all 3 of my lenses as soon as I got it but I fixed it myself and you can too if you're feeling a little brave.
It's a fair bit to type up but if you want to give it a go let me know and I'll post how to do it.

Brad

[TomB]

Maybe you could look at my posts about fixing AF on A350 here:
http://www.photoclubalpha.com/forum/vie ... 967#p17563
http://www.photoclubalpha.com/forum/vie ... 967#p17692

[stroberaver]

Thanks guys for your help. I'm not confident enough to fiddle with the three screws while the camera is in warranty, so it's going back to Sony's central service facility next week. Just spoke to them today, and was surprised to find that they don't want any lenses at all - just the camera body.

I took part in my local camera club's flash portraiture night recently and my camera was just useless - with wide apertures the model's eyes were consistently out of focus while her shoulders were tack sharp.

[stroberaver]

Well, I got my camera back this weekend. Sony Central Service in the UK have had it for just under a week to fix the strong backfocus problems. In the fault description, I also linked them to this thread for the sample images.

The following is what was printed on the despatch note:

FULL FOCUS ADJUSTMENTS DONE.

FOCUS GOOD WITH SHORT LENS BUT NOT LONG. USING EDF ALL SHIFT PROG TO ADJ. +10,+50,+50

HIS [THIS?] SHOULD MAKE CAMERA BETTER FOR ALL DIFFERENT LENSES

Can anyone enlighten me what the +10,+50, +50 means?

As for the camera now... it's WORSE!!!. When it comes to wide aperture lenses, right now I have a very expensive black paperwight that resembles an A700.

Do Sony not test these cameras before they send them back? I'm absolutely furious that I've been without my camera while I could've been using it for work, only to receive it with worse focus than when I sent it in. I'm now seriously regretting touching Sony in the first place. Should've just got a bloody Nikon or Canon like everyone else.

I don't need a fancy test bench or lab to see that the focus on this camera is now screwed beyond all practical use. Instead of strong backfocus, I now have front focus to an extent that is almost off the scale. I set up a few targets, with my A700 box in the middle. Nice, high contrast to lock onto with the central sensor - the subject under the central sensor being the right hand edge of the lens pictured on the box. Here's the Sony 70-300 G SSM @ 70mm f/4.5, which was the biggest problem with backfocus:


Looks ok, but f/4.5 probably gives sufficient depth of field to hide any focussing errors here. Let's look at my older Sigma 70-300 which goes slightly wider at f/4:


Oh dear. Can it get worse? You aint seen nothing yet...

Minolta 50/1.7 @ 1.7:

[stroberaver]

Minolta 50/1.7 @ 2.8:


Tamron 90/2.8 macro @ 2.8:


And most significantly of all, here's my walkaround lens - a Tamron 17-50/2.8 at the oft-used portrait settings of 50mm & f/2.8:


Will be interesting to see what Sony have to say about this tomorrow. Good thing they sent a questionnaire back with the camera. I feel that a letter of complaint should be accompanying it.

But that won't get this camera fixed. Any thoughts/opinions/suggestions much appreciated.

[Javelin]

man in all those pics the line between the box on the right and the box in the middle is so sharp it hurts my eyes especially when I look between the blue and orange.

[01af]

Well, I got my camera back this weekend. Sony Central Service in the UK have had it for just under a week to fix the strong backfocus problems. [...] As for the camera now ... it's WORSE!!! When it comes to wide-aperture lenses, right now I have a very expensive black paperwight that resembles an A700.

You've sent your camera in once? And you expect them to get the problem fixed at the first attempt?

I sent my Dynax 7D in six times for getting the back-focus issue fixed. The whole procedure took more than half a year. So calm down and be patient, your odyssey has just begun.

-- Olaf

[KevinBarrett]

man in all those pics the line between the box on the right and the box in the middle is so sharp it hurts my eyes especially when I look between the blue and orange.

Lol, those are two crops in the same jpg.

I wonder about your test, Stroberaver. Some of those lenses have a slight curvature of field (especially at close focus) and will likely show exaggerated FF issues when examining the focus of objects in the periphery. The a700 box has few details in the actual center focus area, as well--it needs to be filled to have a most accurate test, and unless your resized pictures at the center of each example are uncropped, there's no way you're covering the central AF sensor.

To redesign the test, I might stand the a700 box on end and focus on the lens mount of the camera pictured there. This will give you a narrower target to put the corners of your other boxes against. Also, shooting down at your targets further complicates matters. Try getting exactly level with and perpendicular to your middle target.

[stroberaver]

You've sent your camera in once? And you expect them to get the problem fixed at the first attempt?

I sent my Dynax 7D in six times for getting the back-focus issue fixed. The whole procedure took more than half a year. So calm down and be patient, your odyssey has just begun.

-- Olaf

lol, thanks for the reassurance of going through this procedure! Can't believe you had to send it in so many times. I'd have been hopping mad.

I'd love to see inside their Service Centre, to see what the procedure actually is to fix the focussing. Hell, if it was an option, I'd seriously consider going in person with my lenses and sitting next to an "engineer" (I use the term loosely following the mess they've made of my camera) while they are tested and calibrated.

Why is it that everyone at my camera club, who has Canons or Nikons, has never experienced any focussing problems? I borrowed a Canon 40D + 70-200/4 L USM for some motorcycle racing while my A700 was away, and yes the 40D+70-200/4 is a speed machine when it comes to focussing and fps, but it wasn't just the speed of the focus that startled me - it was the accuracy.

Something that cannot be said of my A700 in it's present (useless) state.

I wonder about your test, Stroberaver. Some of those lenses have a slight curvature of field (especially at close focus) and will likely show exaggerated FF issues when examining the focus of objects in the periphery. The a700 box has few details in the actual center focus area, as well--it needs to be filled to have a most accurate test, and unless your resized pictures at the center of each example are uncropped, there's no way you're covering the central AF sensor.

I understand what you mean about the curvature of field, but can't see how that can have anything to do with just how blurry the orange Sony box is when that's what I was focussing on.
Yes, the thumbnail picture is the entire frame. The central focus sensor was lined up over the edge of the lens on the box, and would comfortably cover the rest of the lens too.

I can try again using a different side, but I can't get level with it for now. I had an operation on my knee last week to repair some cartilage and I can't bend down to look through a camera at table height! In a week or two I should be able to, but I'll have told Sony what I think of their "repair" service by then.

[TomB]

Even if you don't take into account the DIY solution, you may try the focus test chart here: http://focustestchart.com/focus21.pdf Put your camera on a tripod, tilt it down to 45 ° by using a water-level, then align the chart on a table.

[David Kilpatrick]

First of all, the adjustments Sony Service made seem quite extreme. I do not know exactly what the parameters mean, but +50 is a big shift. The results you show look like a recalibration error.

However there are other issues present. They calibrate at roughly two metres, and - most important for you as well as for them - they use a neutral colour target under neutral controlled light. Try substituting the orange Sony box for a blue box and you may be surprised at the difference. To check your recalibrated camera correctly, stand two metres from a neutral subject without any lines or patterns - a good subject is a pebbledashed or harled wall. Another good subject is to place something about one metre away from you, and shoot it from eye level (if you are of average height) on the ground. A fag end or sweetpaper lying on tarmac is a good target, or a fallen leaf.

Check again with that kind of condition instead of the highly coloured arrangement you used. Also, turn off DMF and do not use C or A focusing, use S but be sure to press the shutter soon after focus locks.

I didn't find the Canon 40D especially wonderfu with the 70-200mm f/4, by the way. Superficially it seems to focus fast and accurately but it doesn't get any higher a success rate that a normal A700. Check out my real live action test - tracking a dog running across, not towards the 40D at max fps rate:

http://www.pbase.com/davidkilpatrick/image/88642695

David