A57 or A65?

123Mike · May 31, 2012

I think it's great having discussions. I wish some people wouldn't be so self-entitled and assume they know best.

I think I've brought up a few interesting points that are not weird. I think it's perfectly reasonable to think that the focus is set back a little. No-one has been able to say that that does not make sense.

Also, some think that the A77's AF adjust feature is about fixing or adjusting lens errors, which is what I think it is NOT all about. I think it's about choosing to set how far back you want the actual focus to be. Lenses with less depth you can afford to set back. I know that's not taking f stop into consideration, and that's all very crude. It's a nudge, more or less.

The Minolta 28-135 has a shallow DOF, even when bumping up the A a bit. The kit lens has less DOF. Each you'd want the focus to sit a little different.

If someone disagrees with that, then I'd like to hear a different rationale. I could learn something. But I bet that all this is food for thought, and I bet I'm bringing up things here that makes people stop and think. I don't think any of us is really on top of all of this at all.

123Mike · May 31, 2012

sybersitizen said:
123Mike said:

I disagree that some lenses backfocuses more than others. I think anyone that says that is wrong about this. The lens has no intelligence. The camera is observing the image, and it is the one that is instructing the lens' focus back or forth.

Click to expand...

123Mike said:

The A65 appears to be backfocusing quite aggressively more so with some lenses than others. My Min 28-135 for instance is practically useless on it. The 55-200 is good on it.

Click to expand...

Do you see how you are now contradicting yourself?

I own three Alphas without micro-adjust, and they don't behave that way. They focus properly with all my lenses as they should. the majority of other Alpha users report no such problems either, although some do. If you have had or continue to have these problems you are a candidate for a micro-adjust camera.

I'm not contradicting myself just because you say so.
My A33 back-focused across the board.
My A65 back-focuses different with different lenses.
Those are my observations.

Perhaps it's a combination of the sensor not being adjusted properly PLUS that perhaps the A65 has a set of built in focus adjustments (nudges) like the A77 has, but then without being able to edit them.

There are also many other reports of people with various Alpha models with back-focus. And it's always back-focus when it's a problem, never front-focus. I wonder why.

123Mike · May 31, 2012

Another thing to be taken into consideration is that there has to be a tiny dead spot/line in between the sensor pixels. Like looking through a bug screen.

More pixels means more border lines, means a larger percentage of the area not being sensor areas.

sybersitizen · May 31, 2012

123Mike said:
It the focus was always spot on, then when you take a picture of someone, the front is always in focus, and 50% of the focused space depth-wise, is spend on the head.

It's desirable to have the focus set back just a tad, to maximize more of the head being in focus while still being able to blur the background, without having to resort to higher f stops.

This theory is just silly, for a few reasons. The main reason it's silly is that I didn't buy my camera just to shoot people's heads. Did you? Do you really believe Sony thought we did and tried to make their cameras accommodate that?

123Mike said:
Perhaps my camera IS defective, and the sensor is set back a tad, and needs adjustment.

Yes, let's go with that theory.

123Mike · May 31, 2012

Why do you think the A77 has an AF adjustment feature?

Kzoozoomer · May 31, 2012

Thanks for the warning!

sybersitizen · May 31, 2012

123Mike said:
Why do you think the A77 has an AF adjustment feature?

Presumably for the same reason that some cameras from other makers have it: the AF system can sometimes do strange things. That does not imply that Sony or any other maker intentionally made their AF systems do strange things.

philbot · May 31, 2012

123Mike said:
Why do you think the A77 has an AF adjustment feature?

Someone has explained it already..

But getting back to your 'intentional' reasoning, it doesn't make sense because the direction of amount of focus shift depends entirely on the subject being photographed, it's angle, etc, etc.. How would the camera know this?

You are basing it on scenarios with a human face, i.e. focus latches on to the nose, so you hypothesize that it's back focussing to pick the eyes up instead, but this is only 1 situation, what happens if the face is turned 90 degrees, the camera still focusses on the nose, but most people would want the eye closest to them in focus, and so Sony should make it front focus..

The only real answer based on many brands and many instances of AF misalignment is that manufacturers follow the simple premise of not trying to second guess and just try to focus accurately on whatever the sensor is pointed at.

philbot · May 31, 2012

John A Cole said:
Hi all. I've been messing around with lots of cameras lately (M4/3's, DSLR's etc.) but for various reasons now I'm looking at the Sony models. If I'm honest I'm much more tempted by the A65, mainly for the much better Oled EVF as the viewfinder is pretty important for me. It seems many favour the A57's 16MP sensor over the A65's 24MP sensor though but I've probably more read this from review sites.

I'd pick it up with the 18-55 kit lens at first then upgrade later to either the 16-80 or 16-105.

I'd be very interested in people's 'real world' use of either camera in helping me choose.

Many thanks

The short answer is, don't get bogged down in technicalities, for most conditions they can be considered close enough to really bring it down to personal choice, pick one up, have a play, see what your gut says, and pull the trigger!

philbot · May 31, 2012

The only area I'd like to see further improved is predictive AF, but in terms of general AF, all SLT's I've tried lately have been amazingly fast and accurate.

ET2 said:
Meshuggah said:

ET2 said:

Even the old A700 had better AF

http://bit.ly/KYKVoy

than the Pentax ones

Click to expand...

fortunately we live in 2012 now so we can buy updated gear, not based on you 2008 thread you dug up rofl.

Click to expand...

The AF on newer cameras is improved from the A700, so the point stands. The AF on Sony's cameras are still much better than Pentax.

123Mike · May 31, 2012

sybersitizen said:
123Mike said:

Why do you think the A77 has an AF adjustment feature?

Click to expand...

Presumably for the same reason that some cameras from other makers have it: the AF system can sometimes do strange things. That does not imply that Sony or any other maker intentionally made their AF systems do strange things.

Why does it have a feature where it remembers something like 30+ lenses, where you can program it to bias the focus for each lens?

Tom2572 · May 31, 2012

philbot said:
theswede said:

philbot said:

there will be a tipping point at which it stops holding on to high contrast detail and apply smudging.

Click to expand...

While this is true ...

philbot said:

This is largely because of the physics, the 24MP sensor is going to start off (at lower ISO) with more image detail, but it decreases as you move up the ISO scale, crossing over the 16MP at some point, and ending up a little bit worse at extreme ISO's.

Click to expand...

... this is not true. There is no law of physics which mandates this.

At a given sensor area low light performance depends on the total light gathering capability and read noise of the photosites covering that area. There is no reason to conclude that a higher photosite density will necessarily affect the noise per area either up or down. It is perfectly possible to create a sensor with higher photosite count and equal light gathering capability per area (in fact it will probably be a slight bit better, as long as photosite quality can be maintained) and comparable read noise performance.

On 1:1 viewing the image from the higher photosite sensor may have more visible noise than the image from the lower photosite sensor, that is to be expected, but there is absolutely no necessity for this to be true when viewing them at the same size relative to the sensor size.

Jesper

Click to expand...

I agree with your theory, which is pure theory, but I think it isn't what was being discussed..

The discussion was about a general statement that a 24MP sensor always produces a better image then a 16MP sensor, so immediately I am only considering like for like, i.e. comparable technology with the only difference being pixel size.

In which case, you have to consider all the non-linear side effects that each smaller site has with regards to noise (based on identical technologies, so read noise and shot noise constraints and parameters are identical).. as well as other non linearities due to structural / physical elements such as microlenses..

I think it's OK to state the laws of physics mandate this, but it has to be in context, which I hope I've just added.. if not, then I retract that, but the principle I am sure is correct.. You can't base a theory on having lower relative read noise on one vs the other, because you'd have to say why less dense sensor wouldn't use the same lower relative read noise design, and the same for shot noise/electronics noise etc..

I largely used http://www.clarkvision.com/articles/digital.sensor.performance.summary/index.html as my source of information many moons ago..

Seems to me it's you that needs to learn how to read. I absolutely did not make a general statement that a 24mp sensor always produced a better image than a 16mp sensor, The general statement that I made was that the a65 will always produce a better image if you are willing to process RAW files yourself than an a57, and I will continue to stand behind that one. And again, I'm standing behind that statement as an a57 owner who also thinks that the a57 produces better in-camera JPEGs than the a65.

Just for grins though, how does your law of physics explain the D800? Is Nikon governed by a different set of laws than Sony is?

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A57 or A65?

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