Depth of Field/Depth of Focus

[Rob C]

Hi Bill

Unfortunate that the topic on the S2 was clamped at the point that it was, but so be it; I just wanted to say to you here that I do not consider myself in disagreement with you at all about the importance of the accuracy of the alignments of the mirror and sensor/film planes, just that as far as the discussion about auto-focussing goes, the problems discussed lie in the front mechanics/electronics and are separate things to the other battles going on behind the lenses and one has to accept them as such.  But of course, both ends of the candle shrink during the burn.

Rob C

[fredjeang]

Hi Bill

Unfortunate that the topic on the S2 was clamped at the point that it was, but so be it; I just wanted to say to you here that I do not consider myself in disagreement with you at all about the importance of the accuracy of the alignments of the mirror and sensor/film planes, just that as far as the discussion about auto-focussing goes, the problems discussed lie in the front mechanics/electronics and are separate things to the other battles going on behind the lenses and one has to accept them as such.  But of course, both ends of the candle shrink during the burn.

Rob C

I could not agree more.

There is a paradox in those systems in the sense that one big part of the equation is not taken into account wich is the sensor plane. I don't stress on purpose the film plane because this is less of an issue, digital exacerbates the focussing.

As Rob point, we have 2 separate "blocks" that have minimum communication between them. As for the mirror, until they don't find a way to implement properlly an electronic viewfinder that I think it is the future (of course if the viewfinder has the required resolution to display with accuracy), the mirror will always be a wick part of the all machinery (without talking about the noise and vibrations).

I've been asking many times about the reason of this CCD limitations nowdays to a point that you have noticed my complete unawareness when it comes to engineering specs, and I assume it; but still I don't feel the question has been completly answered. Why then some compact cameras are using CCD without problem? http://www.luminous-landscape.com/reviews/...s/sam-ex1.shtml.

If they can make sensors that shake, why can't they make sensors that would move on the plane in a dialog with the lens? + the viewfinder in an ideal world.

-----

That said, unless you are doing fast shooting like fashion, sports etc...I think that this focussing debate is completly over exagerate. Now people want car that drive for them, and when the car systems will stop working they will stand like stupid because they forgotten how to take a curve properlly.

Another reflection is that some years ago, many editorials have been acheived by the antique generation of MFD, unperfect and difficult to focus, and did you notice that suddenly the industry stopped to work because of the lack of accurate focus?
Ok, now most of these guys shoot Canon or Nikon, because of the many reasons that have been expressed here extensively. But anyway, there is a learning curve that I'm not sure everybody wants now to deal with.

The problem with all those systems, like face detection etc...is that it just kills the creativity and we end seeing the same pics.

-Everything will be in focus
-Every pic will have a huge DR
-Every image will have a perfect color balance

-and all those pics will be dead boring.

IMO.

[bjanes]

Hi Bill

Unfortunate that the topic on the S2 was clamped at the point that it was, but so be it; I just wanted to say to you here that I do not consider myself in disagreement with you at all about the importance of the accuracy of the alignments of the mirror and sensor/film planes, just that as far as the discussion about auto-focussing goes, the problems discussed lie in the front mechanics/electronics and are separate things to the other battles going on behind the lenses and one has to accept them as such.  But of course, both ends of the candle shrink during the burn.

Rob C

Rob,

Yes, we may not have been on the same wavelength. For correct autofocus, the autofocus sensor and the image sensor must be in alignment. The position of the mirror does affect the image projected on the autofocus sensor (and the image on the viewfinder), but the image on the CCD is not directly affected by the mirror. The depth of focus for a given circle of confusion determines the necessary tolerances.

If the autofocus sensor and image sensor are not aligned, one will have front focus or back focus. The depth of field determines the significance of the focus inaccuracy. The same considerations apply to rangefinder cameras. In his recent comparison of the Leica M9 with the 21/1.4 Summilux to the Nikon D3x with the Zeiss 21/2.8, Digilloyd noted that the Leica could not attain its potential due to focus shift on stopping down and mis-alignment of the rangefinder system. With the Nikon, he used live view, avoiding these problems.

Regards,

Bill

[BernardLanguillier]

The problem with all those systems, like face detection etc...is that it just kills the creativity and we end seeing the same pics.

-Everything will be in focus
-Every pic will have a huge DR
-Every image will have a perfect color balance

-and all those pics will be dead boring.

IMO.

Totally agreed, as I wrote several times, I see a more talent and creativity on flickr from people using compact digital cameras/entry level DSLR than in many official photographic circles.

Cheers,
Bernard

[Bart_van_der_Wolf]

Totally agreed, as I wrote several times, I see a more talent and creativity on flickr from people using compact digital cameras/entry level DSLR than in many official photographic circles.

Hi Bernhard (and Fred),

Totally disagree ;-) . The technique allows to make images that are technically better, so we can concentrate more on the creative side. After all what good is a fine composition of an interesting subject, with the focus and exposure are totally off, beyond repair?

It is still the photographer who makes the difference, which is why comparing a technology driven forum with a photo sharing site is kind of meaningless.

Cheers,
Bart

[fredjeang]

Hi Bernhard (and Fred),

Totally disagree ;-) . The technique allows to make images that are technically better, so we can concentrate more on the creative side. After all what good is a fine composition of an interesting subject, with the focus and exposure are totally off, beyond repair?

It is still the photographer who makes the difference, which is why comparing a technology driven forum with a photo sharing site is kind of meaningless.

Cheers,
Bart

Bart, technology is simply fantastic. I use it all the time. You will see, when I'll have my website finished that my works are very very very technology dependant. That's one part. I don't live in the past. But,

My idea is aimed to an exess of preocupation I perceive about the sharpening, the DR and the ICC etc... I don't mean that those factors are not indeed important but to reach the point to stimulate so much internet? something's wrong there.

I join Bernard, I see many really creative people with very simple cameras and techniques. Also top artists with top gear and technique of course.
But look, if I have a device who is telling me that this subject has to be in focus wherever it moves, makes a little bip with a yellow square when what I want to do is blurring this plan, then I don't buy.
There are IMO tech and tech.
There are real advances, real exciting stuff in a jungle of an enormous amont of marketing useless features.

I don't remember who said that here but: instead of looking to the photographers needs, the manufacturers should look first at the clients needs.

I'm happy with all that technology. I think that we are lucky. But at the same time we should not forget the basics, where all this comes from.
Taking a Leica M and focus manually and not being so sure all the frames will be in focuss, and concentrate on the subject and forget about the result at 100% on the computer is not a bad exercice at all in our ready-made culture.

As I said, tech yes. But I want to go to the toilet by myself thanks.