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Old May 2, 2007, 12:43 AM   #1
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Someone posted a good list of mount tyeps and lens, I can't seem to find anymore....

Seems to me there were slight differences....

Are there? Or esentially and functionally the same lens type?
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Old May 2, 2007, 11:16 AM   #2
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Hi Hayward,

The main difference between the F and FA series are the FA series lenses transmit MTF (Mean Transfer Function -- read lens sharpness/resolution at each aperture) information via a 4 bit chip in the lens, to the camera body. This info is the main criterion for aperture/shutter speed decisions in the MTF Program mode of the K10, and is used to possiblya lesser degree for the P mode in other Pentax DSLRs. The F series lenses don't have the chip.

There are also some feature/build quality differences, but IMO, they aren't that major, and relate to specific lenses. An example of this is the F* and FA* 300/4.5s -- The F*300 is white, has an integral hood,and has a tripod collar while the FA*300 is silver, has a bayonet style hood,doesn't havethe tripod ring, and you don't have to turn AF off to manually focus the lens, just slide the focus ring. Optically, they are essentially the same, tho some have said that the FA* 300 is silghtly tweaked and is better (I've never been able to compare them personally, so I can't attest to this).

DA and D FA lenses have the chip and also have the focus clutch feature which allows a user to tweak the focus manually after AF focus lock without having to switch AF off on the body or slide the focus ring on the lens.

To answer the statement that you raised in your other thread, for any but the FA, D FA, and DA series (I'm not sure about the FAJs), this MTF info is not transmitted, and theMTF program line assumes that the lens will be sharpest at 1-2 stops down from wide open, which is pretty typical.

Scott


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Old May 2, 2007, 11:23 PM   #3
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Yet even with a F lens Two of wich. I have had... one no longer, but sharpness optimum auto setting was not the criteria... the MTFsetting on the K10Dseems to pretty well and accurately pick up ont that on a F lens.... though maybe slightly better on a FA.
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Old May 3, 2007, 2:07 AM   #4
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Hayward wrote:
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Yet even with a F lens Two of wich. I have had... one no longer, but sharpness optimum auto setting was not the criteria... the MTFsetting on the K10Dseems to pretty well and accurately pick up ont that on a F lens.... though maybe slightly better on a FA.
Hi Hayward,

So you're saying what? -- that the F lenses are indeed chipped with MTF data, and it's not quite as accurate as the FA lenses, or maybe, that the K10 body contains a database of lens MTF data and "knows" how to set up the MTF program line for F lenses, or maybe, that it calculates the MTF data for an F lens when one is mounted?

Sorry, but I don't think it's quite that "smart".

Scott
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Old May 3, 2007, 3:25 AM   #5
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snostorm wrote:
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Hayward,

So you're saying what? -- that the F lenses are indeed chipped with MTF data, and it's not quite as accurate as the FA lenses, or maybe, that the K10 body contains a database of lens MTF data and "knows" how to set up the MTF program line for F lenses, or maybe, that it calculates the MTF data for an F lens when one is mounted?

Sorry, but I don't think it's quite that "smart".

Scott
Well I can't say I have scientifically STUDIED it (and is my P mode default program line setting) but F, F/DA or third party the MTF program setting seems to behave the same way. Generally in most situations it chooses one stop over the max FL min f/ value.
(So a F/4-5.6 lens... it goes for F/8 even if at min zoom.)

Or1 stop over min on a prime... though I can only base that on a "A" I haven't had a F or F/DA prime yet.

Again not really scientifically tested if any one wants to disagree with that pattern... go ahead.
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Old May 6, 2007, 5:48 PM   #6
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snostorm wrote:
Quote:
The main difference between the F and FA series are the FA series lenses transmit MTF (Mean Transfer Function -- read lens sharpness/resolution at each aperture) information via a 4 bit chip in the lens, to the camera body. This info is the main criterion for aperture/shutter speed decisions in the MTF Program mode of the K10, and is used to possiblya lesser degree for the P mode in other Pentax DSLRs. The F series lenses don't have the chip.

DA and D FA lenses have the chip and also have the focus clutch feature which allows a user to tweak the focus manually after AF focus lock without having to switch AF off on the body or slide the focus ring on the lens.

To answer the statement that you raised in your other thread, for any but the FA, D FA, and DA series (I'm not sure about the FAJs), this MTF info is not transmitted, and theMTF program line assumes that the lens will be sharpest at 1-2 stops down from wide open, which is pretty typical.

Scott

Very informative.Thanks for posting that.

I assume that the 18-55 and 16-45 kit lenses, since they are in the DA series, do have the chip.

Do you (or anyone else) know if any of the 3rd party AF lenses for Pnetax also have a similar chip (or at least a similar function)?

Would any of these have it:

Sigma 24-135 2.8-4.5 ASP IF

50mm 2.8 EX DG 1:1Macro

Tamron 28-200 3.8-5.6 XR IF Macro

28-300 3.5-6.3 LD IF

70-300 4-5.6 LD 1:2 Tele-Macro

Promaster (same as Phoenix) 100 1:2macro (1:1 w/adapter) (I wouldn't expect itfor this one)
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Old May 20, 2007, 11:13 PM   #7
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According to Pentax the F* lenses are not chipped, while the FA* lenses are.

Tom
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Old May 22, 2007, 2:21 AM   #8
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May well be.... and as someone else mentioned maybe the K10D is just smarter than some before and has a data base/AI in the firmware.... but having had two F lenses and one FA (And a DA I'd guess also do have the chips), the "optimium" exposre MTF setting works EXACTLY the same on both types (chooses same settings), as well as on relatively current third party's like SIGMA/Tamron, etc.. (that fully report FL range, max-min F, etc.)

And actually even on my older prime A's also behaves the same way... though might not on old M and A zooms.... which I have avoided because of the SR/zoom manual proper compensation at each shift (especially if end to end) complications. Again primes easy just 1 set at mount.

And again woud seem to be

Primes 1-2 stops over min. (FL seems to make some difference there)
Zooms... 1 stop over max zoom min (Even when at min zoom.... where likely 2-3 stops over min)
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