A2 misfocus..more ideas?

[Alex Permit]

I've recntly observed cases when the A2 shows it has focus lock, but the focus is off. It seems to happen when I have a very bright subject against a dark background. I thought I'd experiment and see if I can consistently duplicate the result. I did so by trying to focus on a street light. Here are my results

Focus point near light



Focus on yellow body



Focus near the red lighted hand



Focus on one way sign



At times, the focus will just hunt and show no focus when I try focusing on the light. But many times it WILL lock focus. And focus was off in ALL such cases.

The shots can bee seen here
http://www.pbase.com/work_permit/a2_focus_test

 

[Vancemac]

Very interesting, Alex. In my example from another thread, my OOF picture is of a dog... but it is a white(ish) dog on a sunny day, making him a very bright focal point. You might be on to something?

Vance

 

[Alex Permit]

I was out taking shots, when I noticed my A2 horribly misfocused on a bright street sign set against a dark background. I was instantly reminded of your dog shot. I then set out to see if I could reproduce the error. I used street lights as a test.

I found that if I tried focusing directly on the light, the A2 would not find focus lock. But if I tried focusing slightly off the light, it would CONSISTENLY misfocus. I must have tried it a couple of dozen times on different lights. Always got focus lock, always focus was off.

Very interesting, Alex. In my example from another thread, my OOF
picture is of a dog... but it is a white(ish) dog on a sunny day,
making him a very bright focal point. You might be on to something?

Vance

 

[summerwind]

maybe it's the dust.........;-))))

I found that if I tried focusing directly on the light, the A2
would not find focus lock. But if I tried focusing slightly off
the light, it would CONSISTENLY misfocus. I must have tried it a
couple of dozen times on different lights. Always got focus lock,
always focus was off.

Very interesting, Alex. In my example from another thread, my OOF
picture is of a dog... but it is a white(ish) dog on a sunny day,
making him a very bright focal point. You might be on to something?

Vance

--
x

 

[Alex Permit]

The pro-1 misfocuses on long tele shots.

The A2 just misfocuses on street lights

maybe it's the dust.........;-))))
Alex Permit wrote:

 

[LeifShutter]

Now don't move...



--

 

[lhomer]

I have similar experience. Roughly speaking if I direct my focus spot to a region which is fairly uniform (like a light) it will not focus properly, but if I move nearby to say the yellow surface, and catch that dark, contrasting vertical line it does ok. The auto-focus system needs some light/dark contrasts in its view.

I've recntly observed cases when the A2 shows it has focus lock,
but the focus is off. It seems to happen when I have a very bright
subject against a dark background. I thought I'd experiment and
see if I can consistently duplicate the result. I did so by trying
to focus on a street light. Here are my results

Focus point near light



Focus on yellow body



Focus near the red lighted hand



Focus on one way sign



At times, the focus will just hunt and show no focus when I try
focusing on the light. But many times it WILL lock focus. And
focus was off in ALL such cases.

The shots can bee seen here
http://www.pbase.com/work_permit/a2_focus_test

 

[Alex Permit]

I tried to catch the border of light and dark in some shots (like for example the red hand). The A2 would still misfocus. It seems to need light/dark contrast as you say, but it also appears to get "overloaded" if the light are is too bright.

I have similar experience. Roughly speaking if I direct my focus
spot to a region which is fairly uniform (like a light) it will not
focus properly, but if I move nearby to say the yellow surface, and
catch that dark, contrasting vertical line it does ok. The
auto-focus system needs some light/dark contrasts in its view.

 

[lhomer]

Or if the contrasting edges are a bit fuzzy as they are in the hand, because the auto focus system is trying to sharpen up something which is not sharp.

I have similar experience. Roughly speaking if I direct my focus
spot to a region which is fairly uniform (like a light) it will not
focus properly, but if I move nearby to say the yellow surface, and
catch that dark, contrasting vertical line it does ok. The
auto-focus system needs some light/dark contrasts in its view.

 

[OzRay]

I've found that there are certain subjects that the A1/A2 do have difficulty getting a focus lock on. This is probably due to the contrast method that the autofucus is based on (as I understand it) and subjects with low contrast are a problem - the subject can be very bright, but not have enough contrast.

If you understand the limitation (not camera defect) of this method of focus determination, then you can consistently get sharp photos. Once I learned the limitations, and it wasn't hard to do (just practice), I now rarely get a shot that's poorly focussed. When I do, it's just me stuffing up.

Cheers

Ray

--

There are no limitations, only challenges - me (unless someone else said it first).

http://www.rkp.com.au/PhotoGallery/

 

[summerwind]

No, it focuses perfectly, but it does have a harder time to get a lock when in low light at any zoom length over 85mm........but when it says "go", rest assured it is in perfect focus.

The A2 just misfocuses on street lights

maybe it's the dust.........;-))))
Alex Permit wrote:

--
x

 

[summerwind]

now that's a good one..............it's the reason i still want an A2........just gonna wait a bit longer.
i know Minolta will have the newest firmware version out soon.

Now don't move...



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--
x

 

[x2h229497]

It's a problem with any AF camera.

 

[djedi]

No, it focuses perfectly, but it does have a harder time to get a
lock when in low light at any zoom length over 85mm........but when
it says "go", rest assured it is in perfect focus.

Tried a Pro1 at Best Buy before buying the A2.

Yes, when it says it is in focus, it really seems to be. Only problem is, every time I tried to get it to focus on a moving subject, the subject was out of the frame before it focused- and then on something in the background.
It seems to be a great camera as long as the subject doesn't move.
Djedi
--
frustrated photog

 

[sparrowminded]

Thank you! I used a 35mm Oly IS-20 for a long time, and still have it. It trained me to locate my focus point at the intersection of contrasting horizontal and vertical lines. My oldish Canon EOS Rebel is more refined, but the same holds true.

As noted in other threads, once you locate focus and exposure at a point selected this way, press the shutter button halfway, to lock everything, then frame and shoot quickly. Your A2 will suddenly become far more agreeable.

It's a problem with any AF camera.

 

[lhomer]

Amen. My A2 does a better job than I do. On good targets we are close to equal. On poorer targets it is consistently better than I am, and I am sure I cannot do a good job where it won't lock. What I can do with my eye is roam the scene for a good target.

It's a problem with any AF camera.

 

[Alex Permit]

A number of people have been complaining about oof shots with the A2. My impression is that the shots tend to be of bright subjects. Shots like this one



My experiments are meant to "reproduce' these errors.

It's a problem with any AF camera.

 

[vrobertg]

Hi Alex: Have been following the focus issue as of late. Interesting about the out of focus street light & the othewr street signs. If you could get a similar day & the dog to cooperate why don't you try focussing on its nose or collar. Just for the H _ _ L of it. Oh I just realized you are probably not the photographer w/ the dog are you. Well if he or she reads this post perhaps they'll give it a try.

Sorry if I was wrong, Vince

 

[angryofmayfair]

focusing on the light. But many times it WILL lock focus. And
focus was off in ALL such cases.

Alex this is excellent work - thanks!

And I think the above quote is the real crux of the matter - the fact that we get focus confirmation when the subject is (not always obviously) OOF.

I accept that the A2 cannot always determine the point of focus, that's not the problem and in this respect it's probably no different form all/most other af cameras - it's the fact that it actually gives the wrong information of 'correctly focussed' when in fact nothing is in focus...

--
http://www.canons1.MinoltaA1.photoshare.co.nz

 

[Box Brownie]

Hmmm!!!!!

Like some others here I am becoming convinced that the OOF issue mainly lies in trying to focus on objects with minmal or low contrast between light and dark areas ~ my understanding is that the focus relies on 'phase contrast' to determine a sharp point.

Yesterday, I was photographing my great nephews (3 and nearly 1) all with flash. The shots that are sharp are where they were (relatively) still so I could concentrate on getting a stable focus lock. Where they are OOF it is either because they moved or the A2 confirmed lock whilst attempting to focus on areas of the face without sufficient contrast.

I will be examining the images more closely to weed out the ones not worth PPing and try to get more of a feel as to what went wrong.

Now as to why the camera declares a focus lock when in some cases the shot is visibly OOF in the EVF escapes me. I have 'grip off' ; single shot AF ; cont AF off ; AS on. It does make me think that if KM are monitoring forums such as this that they might introduce a firmware update that tries to solve the issue. Incidently, some of the pictures where I saw the EVF was OOF and re focused are better.

I have discovered that FFP focus is a very small zone (I have photographed flowers sharply through shrubbery) and the normal focus area (that is so bad at getting the right subject) is very large. I think we need a third level of focus zone i.e.larger FFP (just that little bit larger) so that there are more pixels involved in grabbing the focus contrast. Firmware update maybe???

Just a thought to close on ~ with my old EOS650 I was very used to focusing and recomposing, so I wonder if subconsciously I am expecting too much of this great camera in the focus department and need to take on board Michael Reichmanns comment in the Bull Fighting article about setting the focus manually with an aperture sufficient to ensure that all in the zone will be sharp. But could I have done that with flash shots?

As he also says elsewhere "Practice Mutha, Practice"

: )