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09-07-2010, 06:03 AM   #16
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Can this be seen on youtube? (Win2000 here)

09-07-2010, 01:50 PM   #17
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QuoteOriginally posted by falconeye Quote
Was it just me or did the Penatx rep say that:

FA 645 <=> FA*/DA*
FA* 645 <=> better than FA*/DA*

optical quality?
That's what he said. I read it as the resolving power of he 645 lenses is greater than that of their 35mm equivalents. You get better glass for your $12,000. Makes sense.
09-07-2010, 04:11 PM   #18
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QuoteOriginally posted by Aristophanes Quote
That's what he said. I read it as the resolving power of he 645 lenses is greater than that of their 35mm equivalents. You get better glass for your $12,000. Makes sense.
Ok, let's take that for granted for a second. Except that the price difference goes by larger lens element diameters, not better glass. Equivalent lenses cost the same. But then, two different interpretations are still available:

1. Better resolution overall (in LW/PH), where the larger image circle helps as well.

2. Better resolution absolute (in lp/mm), so would even outperform it's APSC or 35mm peer.

From what he said, we cannot differentiate between the two. Only the second option would be interesting for adapting to a smaller mount.


I imagine (with the possible exception of the 600mm lens) that the 645 glass is better because equivalent lenses (same field of view and same diameter in mm) have always better performance for the larger format if the optical formula is comparable (in #elements and kind of glass). For a room-size format, even a pinhole lens is good...

I can see that the A* 645 600/5.6 ED is an interesting lens with a complex optical formula (for a prime). Are there any published MTF figures for it? And is there any other prime lens from Pentax with ED glass? Maybe, this lens deserves special attention?

Last edited by falconeye; 09-07-2010 at 04:19 PM.
09-08-2010, 12:19 AM   #19
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Well I thought the * would mean better in several ways but not only in optical way.

Funny video where they talk more then a minute about how amazing our hyperprogram is. Old folks wich are loosing their touch with new generations in my opinion.

09-08-2010, 01:34 AM   #20
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QuoteOriginally posted by RonHendriks1966 Quote
Well I thought the * would mean better in several ways but not only in optical way.

Funny video where they talk more then a minute about how amazing our hyperprogram is. Old folks wich are loosing their touch with new generations in my opinion.
No hyperprogram is a really a sweet feature, overshadowed by the auto mode while it better. I use it 99% of the time I make casual photography or when DOF is not so important. HP tries to put the camera in F8 while trying to preserve shutter speed. It's like the "set in F8 and forget about it", only in better. And as said in the video, it is very easy to overrule it to shutter priority, aperture priority of full manual mode.

HP is maybe an "old" mode, but like using primes, it's not because it's old fashion that it's not intelligent.
09-08-2010, 05:34 AM   #21
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QuoteOriginally posted by RonHendriks1966 Quote
Funny video where they talk more then a minute about how amazing our hyperprogram is. Old folks wich are loosing their touch with new generations in my opinion.
It's amazing when it works, on the K-7 it's still somehow broken but since I hate the mode dial lock I learned to use it and love it. It's much quicker than moving the dial to Av or Tv.

TAv and Hypermanual are also great features. It's amazing how Pentax got it right for the UI. That's maybe the best feature of Pentax DSLR.
09-08-2010, 07:29 AM   #22
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QuoteOriginally posted by falconeye Quote

I can see that the A* 645 600/5.6 ED is an interesting lens with a complex optical formula (for a prime). Are there any published MTF figures for it? And is there any other prime lens from Pentax with ED glass? Maybe, this lens deserves special attention?
Do you mean just for 645 or for K mount as well? ED glass is quite common for A* and newer Pentax telephotos but from what I understand, manufacture costs using ED for larger lens designs is outrageous. Pentax Extreme Telephoto Prime Lenses


Curiously, the FA31 Ltd and DA15 also use ED glass.....

.
09-08-2010, 08:59 AM   #23
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QuoteOriginally posted by falconeye Quote
Ok, let's take that for granted for a second. Except that the price difference goes by larger lens element diameters, not better glass. Equivalent lenses cost the same. But then, two different interpretations are still available:

1. Better resolution overall (in LW/PH), where the larger image circle helps as well.

2. Better resolution absolute (in lp/mm), so would even outperform it's APSC or 35mm peer.

From what he said, we cannot differentiate between the two. Only the second option would be interesting for adapting to a smaller mount.


I imagine (with the possible exception of the 600mm lens) that the 645 glass is better because equivalent lenses (same field of view and same diameter in mm) have always better performance for the larger format if the optical formula is comparable (in #elements and kind of glass). For a room-size format, even a pinhole lens is good...

I can see that the A* 645 600/5.6 ED is an interesting lens with a complex optical formula (for a prime). Are there any published MTF figures for it? And is there any other prime lens from Pentax with ED glass? Maybe, this lens deserves special attention?
Yup, all interesting stuff.

Maybe they use Kobe glazing sand that is hand massaged by monks before being fired?

09-08-2010, 04:50 PM   #24
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QuoteOriginally posted by smc Quote
Do you mean just for 645 or for K mount as well? ED glass is quite common for A* and newer Pentax telephotos but from what I understand, manufacture costs using ED for larger lens designs is outrageous.
[...]
Curiously, the FA31 Ltd and DA15 also use ED glass.....
I had a wrong impression about how common ED glass is in Pentax primes. Must have been the Bokeh fringing which Pentax doesn't seem to worry about as much as some expesnsive designs do.

Actually, I see these ED primes now:

DA primes:
DA 14/2.8
DA 15/4
DA* 200/2.8
DA* 300/4

FA primes:
[F]A* 200/2.8
[F]A* 200/4 Macro
[F]A* 300/2.8
[F]A* 300/2.8
F[A]* 300/4.5
A* 400/2.8
FA* 400/5.6
F[A]* 600/4
A* 600/5.6
A* 1200/8

FA 645 primes:
300/4
300/5.6
400/5.6
A 600/5.6

Interestingly, the FA 645 200/4 lens isn't ED and doesn't carry the prime designation while all 35mm FA*200 do.

So, I guess, 645 glass isn't superior by construction. Only by having the larger image circle to help relative resolution.

I don't see ED with the FA 31/1.8 though, just an aspherical element. Dimitrov lists the FA31 as ED but Pentax doesn't. I assume a mistake on Dimitrov's part.

Biggest ED lenses are 600/4 & 1200/8 which is 150mm diameter But again, 645 is not exceptional.
09-08-2010, 06:11 PM   #25
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I have a couple of those lenses, but I wouldn't know how to go about testing them to see if there is a difference....
09-09-2010, 01:18 AM   #26
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QuoteOriginally posted by falconeye Quote
I had a wrong impression about how common ED glass is in Pentax primes. Must have been the Bokeh fringing which Pentax doesn't seem to worry about as much as some expesnsive designs do.

Actually, I see these ED primes now:

DA primes:
DA 14/2.8
DA 15/4
DA* 200/2.8
DA* 300/4

FA primes:
[F]A* 200/2.8
[F]A* 200/4 Macro
[F]A* 300/2.8
[F]A* 300/2.8
F[A]* 300/4.5
A* 400/2.8
FA* 400/5.6
F[A]* 600/4
A* 600/5.6
A* 1200/8

FA 645 primes:
300/4
300/5.6
400/5.6
A 600/5.6

Interestingly, the FA 645 200/4 lens isn't ED and doesn't carry the prime designation while all 35mm FA*200 do.

So, I guess, 645 glass isn't superior by construction. Only by having the larger image circle to help relative resolution.

I don't see ED with the FA 31/1.8 though, just an aspherical element. Dimitrov lists the FA31 as ED but Pentax doesn't. I assume a mistake on Dimitrov's part.

Biggest ED lenses are 600/4 & 1200/8 which is 150mm diameter But again, 645 is not exceptional.
Even in the Photozone tests, "Bokeh Fringing" never worried me much. I would like to see "real life" pictures with and without this issue to admit that it does matter.

Chromatic aberrations in focus and overall quality of bokeh are more important to me anyway.
09-12-2010, 11:05 PM   #27
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The Pentax rep. also talked about film being a deeper image forming medium compared to the rather thin sensitive planes of digital sensors.

Does this explain why PF ("Pentax fringing" aka "purple fringing" ) has become more visible in the digital age (or is that observation not even true)?
09-13-2010, 05:48 AM   #28
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QuoteOriginally posted by Class A Quote
The Pentax rep. also talked about film being a deeper image forming medium compared to the rather thin sensitive planes of digital sensors.

Does this explain why PF ("Pentax fringing" aka "purple fringing" ) has become more visible in the digital age (or is that observation not even true)?
I think they indeed pointed one of the reasons. The other reason would be that :
1. Modern Digital sensors show more detail than color films commonly used. Thus making purple fringing a bigger issue.
2. People look at images at a much higher magnification than they ever used to with film. 100% viewing on a 24" screen is a detail a hudge print. Compare it with a contact sheet ...

IMO, there's a mix of all, like with resolution and DOF, those issue are very much related to the size of the viewed image. The same image will seem perfect in a Web vignette at 72dpi with a significant DOF, and will show a much thinner DOF, with eventually purple fringing and other issues on an A3 print at 300dpi.

What you demand from your camera and lens ultimatly depends on what you intend to do with the image.
09-14-2010, 02:44 AM   #29
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QuoteOriginally posted by Class A Quote
The Pentax rep. also talked about film being a deeper image forming medium compared to the rather thin sensitive planes of digital sensors.

Does this explain why PF ("Pentax fringing" aka "purple fringing" ) has become more visible in the digital age (or is that observation not even true)?
I noticed that remark too.
But I'm undecided if this is the case or maybe an urban legend among digital camera designers.

35mm film uses a transparent support layer which is 130Ám thick and between one and four emulsion layers per color 5-20Ám thick each. On top may be a 3Ám protection layer. It was a design goal for film to make the overall emulsion layer as thin as possible because a thick layer led to fuzzy images, mostly because of reflections between layers. A typical value given for the overall thickness of the emulsion layers is 15Ám. That's 3x the width of a K-7 pixel.

I don't know if the order of color-sensitive emulsions is standardized. Wikipedia writes: "typically the blue-sensitive layer is on top, followed by the green and red layers". So maybe, the exact focal planes for the three prime colors are 5Ám apart. A lens optimized for film may then have a small defined longitudinal CA as a design goal in consequence. It would translate to ~1 pixel extra CA at f/1 on digital.

Other than that, a finite layer comprising the focal layer would appear to be sharper than a thin layer just out of focus by the finite layer thickness indeed. But not as sharp as the thin layer in focus. Therefore, the maximum in contrast with perfect focus is more like a sharp peak with a thin layer and more like a hill top with a thick layer. But one really would have to look into this in greater detail in order to say that digital is more difficult to focus for.
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