MTF program line

<p>Greetings!<br>

Does anyone have any experience using the MTF program line? MTF program line "prioritizes the best aperture settings for the attached lens". And I'm guess (from reading the manual) that it matters only if you are in the Green or Program mode. I hardly ever use the P mode (never used the green mode!) but am real curious about this. Time and time again I read about how such-and-such lens is fine/ok/good but best/better/great when stopped to Fx/Fx/Fz. So does this mean by using that feature it will automatically set the lens to the sweet spot? I would be real curious if someone can try it out on the infamous 50mm 1.4 or 1.7s cause everyone always says how its better to be 2 stops down.<br>

Anyways, slow day at work, reading up on the manual online... I guess next time I should bring my camera to work so that when its slow I can atleast play with it... though that probably won't look good...<br>

Oh it only works with DA, D FA, FA and FA J. No DA*?<br>

Thanks!</p>

<p>I'm not sure what lenses it works with, but I would imagine at most it would be F series onwards, and only Pentax lenses, of course. What I don't know is how it works with lenses that are produced after the camera has been given its last firmware upgrade, because as far as I know Pentax lenses are not chipped in any way and thus can't carry the MTF information with them. If someone knows anything to the contrary, I'd like to hear about it.</p>

<p>Somanna, just about every lens performs at it's best 2 stops down from maximum aperture, but that doesn't necessarily mean that performance is bad at other apertures, just not the best. In any case, you need to shoot the aperture you need to shoot, so don't fret over "idel apertures" too much unless you're trying to achieve maximum DoF and don't want to run into diffraction effects.</p>

<p>So I wonder if that MTF line does stop lenses 2 stops from max? Don't worry, I don't fret about ideal apertures, in fact I don't even zoom into my photo to double check sharpness on the corner or some random wall or tree!<br>

For example, people have said that for the kit lens the "best" aperture is 8-11, so will MTF choose that? And that lens should work, since its a DA (see the last line of my original post). For me, I have not noticed differences to that magnitude, let alone catch diffrations!</p>

<p>You can see graphs of what the various program lines do with the 24-90 lens on pages 111-113 of the the MZ-S user manual, available at the Pentax USA ste. I think P mode is genius. Turning the aperture dial shifts the camera into Av mode. Turning the shutter dial shifts it into Tv mode. Why doesn't every camera work that way?</p>

<p>My k20 is set up for MTF program line and while I have not done any formal testing I find it seems to green button any given lens' aperture to about two stops down from wide open on most every lens. Being able to bias program high shutter speed, sharpness, or wider apertures does it make it a more useful feature for fast paced shooting.</p>

<p>The PZ-1 and MZ-S had MTF program line capability as well. I think I would be more likely to use the different program lines if they were more easily accessible & not buried in a custom setting. Yet one more thing I'd rather use that RAW button for.<br>

I believe that MTF data is not available with F lenses; it was added with the 'advanced lens-body digital transmission' with FA glass--so I believe it is built into the lens and doesn't necessarily rely on camera firmware. Not sure if you have a K10D or K20D but it is likely that there were no DA* lenses available yet when the K10D was released. Anyway, it is safe to say that DA* are like DA in this regard. I suspect that many of the third-party AF lenses are probably 'F'-capable but perhaps not FA, though I'm not sure about that.<br>

<a href="http://www.bdimitrov.de/kmp/technology/summary/index.html">Boz's site says</a> the MTF wasn't in the FA J lenses but it may be in error. I wouldn't be all that surprised if his chart should actually have shown FA J ('crippled' KAF) as an offshoot of FA (KAF2) instead of F (KAF).</p>

<p>By the way, does anyone else hate the new p-net text editor that shows paragraph breaks that won't show when the page is rendered? I craft these beautiful paragraphs, then p-net crams them together. (grrr)</p>

<p>I think all A and up lenses work with it, but this fact I am not sure about. I am certain F and FA, and DA lenses do work with this function.</p>

<p>However, it is not known just how much data is input.</p>

<p>For instance did pentax get the MTF for all zooms ranges and focus distances, or just for certain zoom lengths.</p>

<p>Or is it just a general, f/5.6-f/11.</p>

<p>No one that I've seen post actually has a definitive answer. But you can take a look at the test on photozone, or other lens testing sites (photodo, slrlensreview) and get sharpness at most apertures to figure out what your lens sweet spots are.</p>

<p>However, the testing for lenses is at certain distances and not the whole range. So while f/5.6 might be sharpest at infinity f/8 might be sharpest at 4 ft.</p>

<p>It's actually why I am very excited about my Voigtlander 90mm Lanthar. It is one of the most consistent lenses money can buy. Equally sharp at close focus, and at all apertures.</p>

<p>MTF program for the 90mm Lanthar is whatever you feel like!!!!</p>

<p> </p>

<p>Well Andrew erased my certainty. About A lenses, I still was under the impression F lenses had this, ability. Perhaps the camera is just using middle apertures when set to MTF with these lenses?</p>

<p>I'm pretty sure "A" lenses don't have the chip, as the body still queries for the focal length with the A lenses I have.<br>

However with F (and up), the body doesn't ask for the focal length, because the lens can report it (even zoom lenses). One of the pins on the mount is used for a serial protocol to transfer the MTF data and currently used focal length. So F lenses at least already have a chip.</p>

<p>If you look at <a href="http://www.bdimitrov.de/kmp/technology/summary/index.html">Boz's site</a> , more information is reported by FA and newer lenses--including MTF and focal length at which lens has minimum size (for power-zoom auto-retract, probably only implemented on a few Z/PZ-series bodies). I would assume that if MTF data isn't available for a lens, the body will either just use the standard program line (which seems more likely to me) or perhaps has a default to stop the lens down two stops if it can.</p>

<p>Justin, those Voightlander lenses are pretty sweet-looking, including that 90mm Lanthar. I've been thinking it would be pretty awesome on film too. I actually think that wouldn't be a bad spec for another DA Limited telephoto. It's a shame that they've been discontinued.</p>

<p>the following are prewritten articles about program linme a nd matrix metering.<br>

==========</p>

<p >if you are talking pentax, which i am and own, the program mode can do something automatically that nothing else will. and that is give you the best IQ possible with a certain condition being met at all times. you, the user, has the control of that condition.</p>

<p >the one thing aperture or shutter priority is doing is setting the other while you set the first one. but what it is not doing is giving you best possible picture while the camera is doing it. YOU are deciding that you want f8.0 or 1/125 but that may not give the best pic. which means of course that you have to adjust it to get the best pic at the brightness conditions. in P or program at all times the the best pic is being made but with the condition that you set also met.</p>

<p >what condition? the following are possible: MTF, shutter speed, aperture, DOF. depending on the camera others may be possible. the default is MTF. the way mtf works is that the camera in auto or program, either is being affected by the program line selected. the camera as the light level rises from dark keeps the fstop at wide open till about 1/60 then lets the fstop rise as well. this continues until the lenses reaches max IQ fstop which is going to be f5.6-f11.0. then the camera holds the fstop and lets the shutter speed rise till it is very fast, about 1/1000-1600. then the fstop will also rise. the whole point of this is to put the camera and lens into a normal shutter speed(1/60) then put the lens at its best performing IQ setting and keep it there as long as possible, as the light level rises. this would give the maximum possible IQ the fastest from a dark starting situation.</p>

<p >the other program lines work the same way but the emphasis is on the other subjects. what was described above is the MTF only.</p>

<p >it is for this reason that i let my *istD run in auto almost all the time,with matrix metering. the program line is giving me the best possible pic IQ as fast as it can as the light level rises. if i do not want the selected settings i simply move it to P and set my own with either wheel knowing the combo will still give the correct exposure but it may be at sacrifice in IQ. Or you can run the dslr in P and use the program line as well as changing the shutter fstop combo. i have been shooting slr/dslr for 38yrs. in that time i have found that setting the exposure is just a mechanical exercise. i can do this fairly easily. the hard part is knowing what to shoot so that the subject matter is worthy of having a pic taken in the first place. with the program line set to MTF i know i am getting the best possible IQ in the conditions that i have to shoot in. if i have a situation that requires more dof or a faster shutter speed then that is what P is for.</p>

<p >the program lines can be set via the menu. i leave mine at the default the mtf for max IQ.</p>

<p >if i have a situation that requires a special dof or shutter speed then it is possible to change to aperture or shutter priority. an example would be at an indoor hockey game and using shutter speed priority or any other sporting event.</p>

<p >many times on these forums i read of people who state that they leave their dslrs in aperture priority all the time. fine if that is what they want to do. but at the same time they should know the that the best possible IQ may be at another set of settrings that they do not use. but the program line guerentees that the best possible IQ under the available light conditions will always be set in the fstop and shutter speed.</p>

<p >===========</p>

<p > </p>

<p >matrix metering is the same as averaging metering with an addition. it also includes the use of EC to prevent highlight blow outs. the reason that matrix metering has many segments is as follows- in matrix the meter determines the correct exposure, then checks each segment to see if at that exposure if any have a highlight that would blow, if yes then the meter backs down the exposure so that the segment will not blow any highlights.</p>

<p >so if you have the meter in center weighted and then you are using EC to prevent blowout then the matrix system is doing the same thing. if you are spot metering and seeing which areas are the brightest and setting the exposure that way; well, the matrix system is also doing that for you.</p>

<p >this is exactly why i use matrix almost exclusively on my dslr. the object of metering is to get the correct exposure and not blow highlights, and that is what matrix(evaluative) metering is doing.</p>

<p >once the pics are downloaded to the pc, all that is necessary is to use auto levels in pe6 or csx, or similar in another pp program and the light level of the pic with be restored to normal. and no blowouts. matrix metering is protecting you from making highlight blowouts. let it do it, that is what it is there for.</p>

<p >as far as i know no dslr under or over exposes. </p>

<p >the user must know what the meter is doing how it is doing it why it makes certain decisions how it is processing the info and how it is presenting the info to the user.</p>

<p >unless the above is known any talk of under or overexposing is meaningless.</p>

<p > </p>

 

<p>That option started with the PZ and PZ1p and is usable with the FA and later lenses - these are chipped. Those lenses also reported the focus distance (a Pentax patent that Nikon has licensed for their "D" lenses) and was usable for flash operations.<br>

Bob</p>

<p>I believe focus distance and focal length were actually added with Pentax-F, the first edition of lens->body data transmission. The SF series did things like switch program line when you zoom a lens from wide to tele. Whether the current camera/flash models actually take advantage of the focus distance, I'm not sure.</p>

<p>I was in error, the F series do supply the focus distance but the MTF was introduced with the FA series.</p>