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01-24-2009, 08:50 AM   #346
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I had no idea Pentax AF dated back to 1981 !

I went to Bojidar's fantastic pentax site site and found this camera you mentioned from 1981.

http://kmp.bdimitrov.de/bodies/photos/ME_F_AF35-70f2.8.jpg

So its been just 28 years since pentax had autofocus, I wonder when they'll make a fully fuctional 1.4x autofocus teleconverter? You know, for sale not simply roadmapped. I always thought it had only been 22 years since they had AF with a 1987 issue date. But with an extra 6 years, one might assume an AF 1.4x TC may have gotten made two decades ago? I wonder what the engineering problems are to have taken this long?

I own a Tamron 1.4x MC4 and it auto focuses my slow aperture FA 80-320mm f5.6. So I do know its possible and this Tamron AF TC was discontinued like 5 years ago. I'm told that it offers full compatibility with SDM glass but I own no SDM glass.





QuoteOriginally posted by Pål Jensen Quote
It is written by engineers with diagrams and illustration.

You are confusing AF point with sensors. Each AF point have two sensors; that is what the beam splitter is used for; splitting the beam to each sensor.

It is not correct that AF do not work at aperture slower than F:5.6. It has nothing to with blacking out as stated earlier. It works, but that depends on brightmess and contrast of the subject. It is just that it doens't work consistently enough. This according to Pentax technical paper. It has also been collaborated by user who has managed to get F:8 lenses to AF.

To me Canon F:2.8 AF looks like marketing speak as Pentax had this feature in the first AF SLR, the Pentax ME-F of 1981. It was manually engaged via a switch on the top of the camera body. Canon seem to do this automatically, I wont be surprised if Pentax does that to now that all lens info is transmitted to the camera....


01-24-2009, 09:21 AM   #347
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QuoteOriginally posted by Samsungian Quote
I went to Bojidar's fantastic pentax site site and found this camera you mentioned from 1981.
.


Heres an image of the switch that select AF optimized for F:2.8 lenses proving that Pentax had this on their first AF slr 28 years ago!
Funny, enough they say that the feature is rather pointless and has no real effect! Is that the difference between Pentax and Canon marketing?
Attached Images
 

Last edited by Pål Jensen; 01-24-2009 at 09:30 AM.
01-24-2009, 10:03 AM   #348
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I see a feature for the new K30D on the old MEF Pål Jensen. That old camera had an MP3 player built in as well. Cool!!
01-24-2009, 10:13 AM   #349
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QuoteOriginally posted by Samsungian Quote
I went to Bojidar's fantastic pentax site site and found this camera you mentioned from 1981.

http://kmp.bdimitrov.de/bodies/photos/ME_F_AF35-70f2.8.jpg

So its been just 28 years since pentax had autofocus, I wonder when they'll make a fully fuctional 1.4x autofocus teleconverter? You know, for sale not simply roadmapped. I always thought it had only been 22 years since they had AF with a 1987 issue date. But with an extra 6 years, one might assume an AF 1.4x TC may have gotten made two decades ago? I wonder what the engineering problems are to have taken this long?
And what is the link between the date of the first AF camera from Pentax and your rant abut 1.4x converter? I really don't get it except if the point was indeed the sole rant.

01-24-2009, 10:14 AM   #350
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Aside from this discussion : one of relevant Pentax patents

http://www.google.com/patents/pdf/Auto_optical_focus_detecting_device_and_.p...3jZlNn9N6XSdwA
01-24-2009, 10:29 AM   #351
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QuoteOriginally posted by Samsungian Quote
So its been just 28 years since pentax had autofocus, I wonder when they'll make a fully fuctional 1.4x autofocus teleconverter? You know, for sale not simply roadmapped. .

They made one in 1987; 22 years ago. It even worked with manual focus lenses (thats giving AF!).
01-24-2009, 12:54 PM   #352
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QuoteOriginally posted by Pål Jensen Quote
This figure show the two sensors (a, b) and curves derived from them. It also show that they are in front and back of the film plane and that the (AF) film plane is calculated to be where they cross. It also show what the 2.8 vs. 5.6 is all about; precision in determing top point of the curves.
I am sorry but this is not how modern AF works, be it on Pentax or other makes.

How would they be able to put sensors behind the sensor plane anyhow?
01-24-2009, 12:58 PM   #353
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QuoteOriginally posted by Pål Jensen Quote
It is written by engineers with diagrams and illustration.

You are confusing AF point with sensors. Each AF point have two sensors; that is what the beam splitter is used for; splitting the beam to each sensor.

It is not correct that AF do not work at aperture slower than F:5.6. It has nothing to with blacking out as stated earlier. It works, but that depends on brightmess and contrast of the subject. It is just that it doens't work consistently enough. This according to Pentax technical paper. It has also been collaborated by user who has managed to get F:8 lenses to AF.

To me Canon F:2.8 AF looks like marketing speak as Pentax had this feature in the first AF SLR, the Pentax ME-F of 1981. It was manually engaged via a switch on the top of the camera body. Canon seem to do this automatically, I wont be surprised if Pentax does that to now that all lens info is transmitted to the camera....
Pal, you have to realize that these diagrams are old and relative to a VERY special AF system: this one was entirely located in the lens (the unique 35-70f2.8) and only valid for the ME-F.

They just do not represent how modern AF systems work.

01-24-2009, 01:41 PM   #354
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Nope

QuoteOriginally posted by thibs Quote
Mmm I thought Sony stated (no I have no link, just read reports from other users) that there wouldn't be any new camera until july/august ?

As for sensors, I do not see Sony doing any different than before: they will launch the sensor in their own calera and Nikon almost at the same time. Then Pentax will have to wait 3-6 months to have access to it. Sad but that's why Pentax had to design their own one.
They didn't state that. They just told the press that they will be introducing a new camera the next time they seem them at a press event . Since PhotoKina runs every two years, that just means PMA.

C
01-24-2009, 09:25 PM   #355
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QuoteOriginally posted by Pål Jensen Quote
This figure show the two sensors [...]
My apologies. I have to correct myself. It isn't that you listened to marketing people. Just that the referenced material is outdated.

One thing is for sure: Pentax has the innovative power to surprise everybody

As for today's AF sensors: they all black out at some aperture and this is why it is a GOOD idea to have dedicated wide aperture sensors. This is not marketing bullshit. It is something we all want to have (at least for the central AF point).
01-24-2009, 11:49 PM   #356
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All I know is the Pentax ME-F was not a commercial success at all.
Essentially it was a modified ME Super with a focus assist feature. The dedicated SMCP-AF 35-70mm Zoom with an internal motor AF zoom was one of the worst performing lenses Pentax made. A good friend mine had one and it didn't focus all that well.

As a proof of concept, it had the distinction of being the first among the big 5 Japanese camera makers to come out with something AF related. But the bottomline is it was a flop, especially when compared to the excellent Minolta 7000 a few years later.

+1 to what lol101 has mentioned.
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