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06-11-2007, 07:05 AM   #1
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Program line: "MTF"?

In another current thread, the MTF program line option has been mentioned. I've not explored this option myself yet and would like more info. The K10D user's guide says
MTF priority program is a Program Automatic Exposure that prioritizes the best aperture settings for the attached lens and is more effective when combined with a DA, D FA, FA or FA J lens.
In other words, when used with a Pentax lens. My questions:
  1. What does "MTF" stand for? Anybody know?
  2. How does the camera know what the "best" aperture settings are? Isn't it my job as photographer to know whether I want more or less DOF, a faster or slower shutter? Or is this based on some database of the sharpest apertures for the lens in question?
  3. How does MTF work if I use a non-Pentax lens? Does it revert to Normal program line or something like that?
Will

06-11-2007, 07:23 AM   #2
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Mean Transfer Function I think....

Camera knows because the information is stored in a chip in the lens. Take a look at photozone, or Canon's lens info website - there are charts on each lens.

I would guess it would revert back to one of the other program modes if the lens didn't have that information embedded.
06-11-2007, 12:08 PM   #3
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MTF is "Modulation Transfer Function". You can get a good technical overview here or here, but the upshot is that it's a technical non-subjective measurement of contrast and sharpness. Different lenses have different characteristics at different apertures (and for zooms, focal lengths). The camera either has a database of the MTF charts or can be told by the lens itself-- I'm not sure which. Either way, though, setting the camera to this tells the program mode to prioritize for the best technical qualities the lens can offer.

Last edited by mattdm; 06-11-2007 at 12:13 PM. Reason: fix typographical error
06-11-2007, 12:30 PM   #4
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Thanks, guys. That answers my first two questions. Ccallana guessed at the answer to my third question (does MTF work with non-Pentax lenses) and his guess sounds reasonable; but of course it's not a complete answer as it would be good to know WHICH option it reverts to. Do you know, Matt?

One of the things I wish for in Pentax's next camera is a more informative user guide!

Will

06-11-2007, 12:36 PM   #5
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No idea.

If they made an open source firmware, we could 1) look and find out answers to questions like this and 2) add the data for older and third-party lenses.

Oh well.
06-11-2007, 04:50 PM   #6
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QuoteOriginally posted by mattdm Quote
No idea.

If they made an open source firmware, we could 1) look and find out answers to questions like this and 2) add the data for older and third-party lenses.

Oh well.
Still hoping for that open-source thing? So am I.
06-11-2007, 05:21 PM   #7
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QuoteOriginally posted by mattdm Quote
-snip-
The camera either has a database of the MTF charts or can be told by the lens itself-- I'm not sure which.
According to the gathered wisdom at different forums (fora?) all Pentax lenses since the F models contains a chip telling the camera it's lens ID number, focal length and it's MTF data. It has even been suggested that Pentax measures each lens and thus the data should be individual to each lens. This is something I personally don't believe in but as we love (?) rumours, why not?
06-14-2007, 01:00 AM   #8
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User Guide

Further to your quote " a better user guide" have you had a look at
"Pentax K10D Everything you need to Know..... and then some". Author Yvon Bourque. I purchased it from your side of the world and have found it to be much more clear to follow. It is very in depth and I have found it to be extremely helpful. Beats the Manual by a mile.
Then again........... I am a bit of a newbie at all this Digital jargon.
BTW I had just been reading about MTF about an hour ago.
All the best with it.

06-14-2007, 11:43 AM   #9
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I believe the * lenses have very specific MTF data custom tailored to that one specific lens where as a non * lens would have the same generic MTF dataset as all the rest of the same model non * lenses. Meaning if my DA 16-45 was not the same as yours at f5.6 the MTF data wouldn't know or show it but if it was a * it presumably would.

Does anybody know in terms of real world experience just how much does MTF make a difference? And if the above stuff is correct how much of a difference would that make in the real world.

John
06-14-2007, 11:56 AM   #10
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QuoteOriginally posted by jnorth Quote
I believe the * lenses have very specific MTF data custom tailored to that one specific lens where as a non * lens would have the same generic MTF dataset as all the rest of the same model non * lenses. Meaning if my DA 16-45 was not the same as yours at f5.6 the MTF data wouldn't know or show it but if it was a * it presumably would.
What is this belief based on?
06-15-2007, 10:59 PM   #11
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QuoteOriginally posted by jnorth Quote
I
Does anybody know in terms of real world experience just how much does MTF make a difference? And if the above stuff is correct how much of a difference would that make in the real world.

John
It would only make a difference as far as the best and worst image quality of the particular lens. I'm not even sure how to measure the difference.

Say the best MTF aperture is f8 and you shoot at f5.6. Obviously there is some DOF difference, so you would just have to pixel peep at the areas in common best focus I suppose.

Seems pointless, as so much peeping is.
06-16-2007, 07:36 AM   #12
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QuoteOriginally posted by SpecialK Quote
It would only make a difference as far as the best and worst image quality of the particular lens. I'm not even sure how to measure the difference.
Take a look at the reviews at PhotoZone , where they do exactly that -- measure the differences.

Now, whether you can see any difference is a different story.
06-16-2007, 08:01 AM   #13
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QuoteOriginally posted by Jonas B Quote
According to the gathered wisdom at different forums (fora?) all Pentax lenses since the F models contains a chip telling the camera it's lens ID number, focal length and it's MTF data. It has even been suggested that Pentax measures each lens and thus the data should be individual to each lens. This is something I personally don't believe in but as we love (?) rumours, why not?
I have had it suggested to me that with the standard lenses such as the FA, FA-J, DA and DFA lenses that the MTF data is for that lens type, for example all DA 16-45s have the same MTF data, but the FA*, Limiteds (FA and DA) and one can assume the DA* lenses are all tested individually.
02-03-2008, 10:13 PM   #14
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Hi,

I was just searching around the forum since I had the same question as the original person that posted this thread. There are a couple of points I don't have clear, I 'd appreciate if someone can answer:

I wanted to ask people with 3rd party lenses how is the K10D operating on two things:

1. Is multi-segment metering mode used (when selected)? Or center-weighted metering is automatically set?

2. If you use the MTF option on the Program Line setting, what happens? I mean, Pentax provides a lens' info (MTF data, focal length, etc) on a chip inside the lens. 3rd party glass does that as well?

To the best of my knowledge the manual is not explicit about 3rd party lenses.

Cheers
02-03-2008, 10:58 PM   #15
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QuoteOriginally posted by bombo Quote
2. If you use the MTF option on the Program Line setting, what happens? I mean, Pentax provides a lens' info (MTF data, focal length, etc) on a chip inside the lens. 3rd party glass does that as well?

To the best of my knowledge the manual is not explicit about 3rd party lenses.
From my recollection the manual explicitly states that the lens 'lines' MTF does work with are only Pentax's own AF lenses, http://www.pentaxslr.com/files/scms_docs//K10D_Manual.pdf >> DA, D FA, FA, or FA J lenses. 3rd party lenses only go so far as supporting the AF mount, not the MTF data protocol (if that's the right way to categorize it).

Last edited by m8o; 02-03-2008 at 11:05 PM.
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