Bother with back focussing

[InTheSky]

I have a A700 since the first model available in Canada, and never found any strong problem focusing I am probably a member who have tried a very huge amount of different lenses.

From very old lens to very new lens. the A700 is usually working very good. I have found some difference with different lenses (like trying 5 different beercan), 3 differents 100mm F/2.0, etc. I will say, that the A700 need this little adjustment you can found on the A900 body, but this is for very precise focus (Large aperture, long focal, or Macro, but Macro is always better manually ).

On my side, I'm wishing to get a split screen has I have been able to found for my Minolta 7D. Even if I have started on the digital point and shot world, I don't know why, but this split focusing system is always calling me .

For the focusing speed, I can tell you that every time I have put my A700 in the hand of Canon and mostly Nikon shooter, the first thing they told me was : Wow, the camera is focusing very quickly.

Regards,

Frank

[Javelin]

I had a Canon camera here once that I could make focus and not focus just by turning a lamp on in an already bright room A700 was affected to but not to the same degree. David do you remember posting about a camera getting sort of locked up where it wouldn't lock focus at all after trying to focus on something hard where it hunted for a long time? The same sort of thing happened to me today with the 70-300G. after about a minute of this little bird flitting about and the camera switching focus back and forth I swiched to MF with the thumb toggle. it would not go back into AF after that. tried the switch near the lens mount the lens switch and the toggle and you could hear it engaging and disengaging but nothing worked. switch on/off still nothing. worked the lens back and forth against the mount still nothing, I had to have the camera on and remove and re-install the lens before it would start focussing again. hasn't happened since and never happened before that. has anyone else had this happen ?

[stroberaver]

Thanks David and everyone else for the replies.

In order to improve the test, I've followed David's points - I'm a bit incapacitated at the moment so can't go looking for suitably textured walls to photograph, but the litter test is easy to do. One remote control about a metre in front of me on the ground, one Manfrotto catalogue, one Photoworld magazine plus my Tamron 17-50 @ 50mm/2.8, gives this:


(Focussed squarely on the remote control using the central f/2.8 sensor. Apologies for the lack of crispness - the shutter speed was sluggish and I hadn't realised steadyshot wasn't switched on.)


Thumbnail of the whole frame on the left, with two 100% crops. The plane of focus in this situation is half way between the central sensor and the edge of the frame!

After preparing this image, I feared the central sensor could have caught the edge of the manfrotto catalogue as it was fairly close to the remote. So I reshot with the catalogue slightly further away, and with stabilisation switched on. Much sharper image, but with the same focussing results - plane of focus approximately half way between centre and edge in this test.

I've spoken to Sony who of course were apologetic and could only suggest that the camera comes back in. So it'll go back again, this time with assurances of it being tested further before returning, and being treated as a priroty so I don't have to be without the camera for as long. Ho hum, we'll see. Thanks again for the advice and feedback guys.

On the subject of Canon's focussing and tracking accuracy, well I hated the ergonomics, the bizarre reverse zoom ring and the crappy lcd on the 40D, but despite being a novice at panning and motorsport shots, managed to get a decent number of perfectly sharp, focussed bikes going past at 100mph! I know none of my lenses are speed monsters like the 70-200/4 which just zips from end to end in a split second, but I'm afraid that I do not feel confident I could have got the same images with an A700!




Of course, if Sony could supply me with an A700 that can focus properly in the first place, I would've been able to use my own kit and find out!

[David Kilpatrick]

Yes, it's very badly adjusted and needs completely recalibrating - correctly.

Any camera made will do the motor bike stuff easily. It hardly even taxes the AF if you are panning with a bike, the relative change in distance is trivial compared to a child walking in a garden or a dog playing on a beach. My KM5D was 100 per cent accurate on that kind of shot with a 70-210mm f/4 beercan - and on much more difficult subjects, like steeplechase races. I normally test cameras on equestrian events because the typical horse and rider does not have the very clear sharp constant shape that motor and motorbike subjects present - and for the best shots, you need to be at 45 degrees to a fence.

For some obscure reason, Canon ownership is inextricably linked to shooting identical images of various things whizzing round circuits, and sure enough most shots work fine and they are very impressed because 'it is moving fast'. Try totally random action and sudden movements closer to the camera, and you find that all DSLRS (Nikon, Canon, £5000 or £500) end up in much the same position of missing plenty of shots. The difference is that Minolta owners were always, almost a tradition, more into people/pet/candid/odd stuff photography and not much into track motorsports - maybe because people who like those sports see nothing but Canon, and end up following the herd.

I've never regularly tested Minolta or Sony on motor sports as I am normally in company, and my company has a limited boredom threshold! Also, I was always able to shoot this type of situation without AF.

David

[01af]

I like that category: "odd stuff photography"

-- Olaf

[stroberaver]

Well I got it back again (which is a story in itself) - no real information on what they've done, the despatch note just says "software correction and full functional check".

The "litter" test of the remote control and stuff on the ground in front of me is now accurate again - or at least, as accurate as it ever was.

I've reshot the test of the car parked three or four metres in front of a wall using my 70-300 G SSM - what do you think? Once again in each case the selected AF sensor is placed over the right hand part of the numberplate. Bright day, full wide aperture (f/4.5 @ 70mm, ISO320) and very fast shutter speed so no camera shake. Images are 100% crops with full frame thumbnail in the corner.

Using central AF sensor:
http://i36.photobucket.com/albums/e26/s ... sensor.jpg

Using right hand line sensor:
http://i36.photobucket.com/albums/e26/s ... sensor.jpg

[David Kilpatrick]

It looks perfectly sharp to me. Any softness is down to having neutral sharpening, and maybe a hint of in-camera processing at ISO 320 (which is an optimal speed setting). A little pp sharpening and the detail would pop out of these shots.

David

[stroberaver]

Thanks David. Hopefully I'll get out and about at some point this weekend and put it through some more situations.