MTF Program

it's a bit subjective since it deppends on the conditions of the test so unless lenses have been tested under exactly the same conditions it isn't necessarily valid to compare them.

Generally the results are presented as a graph of MTF against aperture at a given focal length. Invariably there is a peak on that graph somewhere (surprise surprise for most lenses it's somewhere between F5.6 and F11) indicating the best aperture. The idea of MTF program is to bias the exposure to use the apertures where the lens performs best whenever possible.

Same idea as setting Av mode and leaving the lens on F8 unless you need to set something else, but a little more sophisticated.

Thanks again Mongoose, I'm getting the picture. No pun intended . . . but it is topical

No use for older lenses then?

Cheers,

Thanks George,

Your right, as usual, there's far too much information in that link for me to comprehend.

Now if only somebody had said MTF( f ) = 100%*C( f )/C(0) I'd have been none the wiser

I do like the term 'spacial frequency response' better though, I almost understand what that means.

And I thought all I had to do was press the shutter release . . .

Thanks guys, I'll give it a go but . . . now I have another question . . .

Which Pentax lenses provide the info for the camera to choose the right settings?

Regards,

All the FA, FAJ and digital lenses.

G

Personally, I think MTF is a bit of a waste of time. There are few lenses which are not at their best at f8, or close to it. So if you want the best the lens can offer, shoot at f8.

Generally, however, there are other considerations, and provided you use good lenses (which provide excellent results anywhere between f4 and f16) then, all else being equal, I would rather lower the ISO and shoot at f4 than raise it and shoot at f8 (or whatever the MTF says). I think the image quality will benefit more from lower ISO than smaller aperture.

Usually DOF or shutter speed considerations will weigh much more heavily than MTF.

G

Many thanks George
The rest was far to complicated for me

Your answer is clear and easy to understand but at least I now know what it means if I see it advertised on a lens

Thanks George.

Excellent info.

Cheers,

Quite true, but the program line has to be based on something, so why not MTF? It would probably save a lot of faffing around if they just made a program which biases F8 heavily I'll admit, but that is Pentax's choice.

In Sv mode you have finger and thumb control of ISO and Speed/Aperture combination so if you don't like what the program line suggests you can change it in a snap.

MTF program is by no means a killer feature, but as an add on bonus I like it.

I think a program line based on a reasonable minimum shutter speed for the lens in use would be more useful.

G

thats not a bad idea at all, so Pentax firmware writers! listen! we want an option for program line based on maintaining a hand holdable shutter speed at the reported focal length.