MTF Priority program line on K10D

Hi folks
I've deliberately put this in the lens section rather than the dSLR section because I would like to collate a list of what the MTF priority is for each pentax lens.

(Done a search on the forum but this info doesn't seem to be available at present)

in case you're not aware, see p145 of the manual for the info, but to summarise below....

Custom setting menu / Program line can be set to one of 4 options
Normal
Hi speed
Depth
MTF

The MTF setting is "MTF priority program is a Program Automatic Exposure that prioritises the best aperture settings for the attached lens and is most effective when combined with DA, DFA, FA or FAJ lens"

aside : I just had to type all that - why oh why can't you copy and paste from pdf grrrrrr !!!

I interpret that as meaning the maximum aperture (minimum f.no) for which 'good' lens MTF is achieved.

IIRC F-series lenses onwards have some chip / memory inside which stores this info which the camera can make use of. I don't know if 3rd party mfrs store the same data. It could be interesting later to compare MTF test data from places like photozone with what pentax have stored in the lenses as 'good' min f.no !

If you like the idea perhaps you could add your info to the subsequent structured post titled "MTF priority program line database" ? (If you can manage to post in focal length order that should aid readability)

How ? First set up MTF in the custom menu. Then just put your camera in P or Sv mode and press the green button, what's your F.no ?

cheers

No, that won't be a reliable way of getting the data.

P or Sv mode, in MTF mode, will only select the optimum aperture when there is sufficient light, and not excessive light, to allow it.

In other words, it's just biased towards the optimum aperture, but it won't always select the optimum aperture. Often it will be no where near it!

Try it again on a brighter scene and I bet it'll be higher than f2.8.

I'm afraid your database is going to be no good unless you find the actual MTF figures and not what people read off their cameras.

bladerunneruk:
But you can unless you have pdf created from jpegs. Depending on a pdf reader you use, change cursor to a text selection tool, select text, copy and paste. I know it's possible with Adobe Reader (however I don't use it), Foxit reader, Evince (Linux).

I think it depends on whoever wrote the PDF they have control over what the reader can and can't do i.e. full edit. Because of it's fairly open nature PDF access is crackable and the pemissions/ passwords can be changed. Some alternative readers just ignore any passwords.

shim

Hi iceblinker, I've tried this with both lens pointing up to the sky and with lens cap on(!), for P mode, auto ISO covering 100-1600 I get the same result with my 200mm lens : press the green button and I get f4.

if it's really bright and the EV level exceeds 15EV [f4,1/2000,ISO 100]then I would expect either f2.8 to be selected or the settings in the viewfinder to blink. Unfortunately not had much bright sunshine around here recently to check that specific point.

I think you'll find that if you try this out indoors then the test result will be repeatable.

cheers

I suspect that you are mistaken about all of that, or your camera is behaving differently to mine. I tested the mode before I posted my above message on my K20D, including indoors.

I don't understand how you got f4 with the lens cap on with your f2.8 lens. I got f1.4 on my FA 50mm f1.4 with lens cap + P MTF mode + Green button - exactly what I would expect.

Also, when it's really bright and the EV level exceeds 15EV, you should expect either a smaller aperture or a blinking display. f2.8 is a larger aperture.

Also, I'm skeptical that f2.8 is the MTF optimum aperture for the FA35/2.

What you report doesn't make sense to me. What does make sense is that the MTF mode only prioritises the optimum aperture, rather than always selecting it. In other words, it's just biased towards it, just as the High Speed mode is just biased towards the faster settings rather than always selecting the fastest setting.

Can you please check again what you're doing and state what camera model and firmware version you have. Thanks.

I won't be able to test mine again for a few days at least because unfortunately I'm having to return the camera because of a focusing fault.

ps. I would appreciate it if other readers could post their views to either back me up or correct me.


One of these three things must be true:

1. Bladerunneruk is mistaken (that's how it seems to me).

2. I'm going mad (quite likely).

3. My camera is behaving differntly (I thought they were all the same in this regard, but maybe not).

doh !!!

this is what happens when I do things in a hurry at lunchtime !

I should have written.... would expect f5.6 or even smaller aperture.... NOT f2.8 !!!!

rest stands

Please elaborate.