G3 heralds the end of APS-C DSLRs

Started May 13, 2011 | Discussions thread
Anders W Forum Pro • Posts: 21,468
Re: and that's before we talk AF micro-adjust! ;-)

ljfinger wrote:

Anders W wrote:

ljfinger wrote:

Anders W wrote:

ljfinger wrote:

Evidence abounds. Plenty even in these forums from experts.

I still don't see any evidence. Just a claim that it exists.


"All current compact and mirrorless cameras use contrast detection AF, where the lens is racked back and forwards until the camera finds the position that gives the greatest contrast (which signifies being in focus). Their lenses tend to be designed with very light focusing elements that are fast to move so that this process of trial-and-error can be conducted as quickly as possible. Intelligent processing also attempts to minimize the need to hunt too far for focus but there is still some hunting to be done."

"Even with the fastest, lightest lens elements, the trial-and-error nature of contrast detection tends to make it slower."

Why on earth should I consider the DPR an authority on this. They don't even measure how it works any more. Besides, there's nothing in this statement indicating that the frequency of evaluation is not they key parameter. I am still waiting for proper evidence.

CDAF works by guessing, moving, stopping and then determining whether or not the guess was right, and then either moving some more in the same direction if the guess was right or in the reverse direction if the guess was wrong.

No, it doesn't work like that. The motor runs continuously.

And now you know different.

No I don't. Where's your evidence that I am wrong?

Single-area AF-S:
G2: 0.423 second
GH2 (2010): 0.273 second.

These numbers are meaningless. First of all they are largely dependent on the distance they had to go and the speed of the focusing motor.

Same distance, same lens.

Second, they are for static subjects for which focusing speed is irrelevant.

Of course, it's not irrelevant because "static subjects" are often less than perfectly static.

Then the CDAF system fails.

On what grounds? Does focus change when a person changes his or her facial expression? Please try to be coherent and stay at least a bit logical.

Third, most compacts can achieve similar numbers. They're all dirt-slow.

What compacts go equal with the GH2. And which DSLRs are faster?

Most compacts issued in the last 5 years or so are similar, and all DSLRs are faster.

Lots of hot air. Claims and claims but not a shred of evidence. Where are your figures and measurements? I am waiting.

Focusing speed is important for tracking moving subjects, not for achieving initial focus.

See above.

Reports on the forums are not a good overall cross section.

Why not?

Because a much higher percentage of people with problems complain than people with no problems report success.

And? Please carry out the argument to its completion and I'd be happy to prove its lack of validity.

The fact that these cameras have sold in the tens of millions over the years indicates that they are staying sold, which they wouldn't if they didn't work. So they do work.

It just indicates that until now there has been nothing better.

There still isn't.

Please try to stay on the subject. You have great difficiulties with that. In what way does your argument stay valid in view of my counterargument. Old cars and old cameras have sold in the millions. How does that prove that they are superior to modern cars or modern cameras?

Fortunately, it's not a big issue, and they miss far less frequently than CDAF cameras do when faced with challenging conditions.

Depends on which CDAF system you compare with which PDAF system. Which comparison do you have in mind and what publicly available evidence do you have to back it up (and don't show me any more sample images of yours; that's illustrations, not evidence).

I've tried most of them (not the G3, obviously, but its predecessors), and it's really not even close. Here's the G1 versus my 20D and a 20 year old lens.

Yawn. Only your subjective opinion once again.

Yes, CDAF is more accurate theoretically in simple static conditions.

And in practice too.

If the subject has good contrast and the PDAF system isn't working well.


For those that shoot in those conditions a lot, it should be satisfactory.

My PDAF system is not satisfactory to me for the conditions we are talking about.

Then it's broken or horribly poorly designed, or you don't know how to use it.

Nope. There's systematic, publicly available evidence to the contary, and you already know which. PDAF is worse for accuracy than CDAF because it is a) subject to more systematic error ( the multiple path problem), b) subject to more random error (because its sensors and and control system aren't as accurate as those of CDAF). I have a lot evidence for both conclusions. Where's yours?

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