[Spodeworld]

So, to be sure, are you saying that the Green button doesn't work (e.g. in Manual mode set shutter speed) with an F but will with an FA?

Thanks.

For most uses, the main difference between the F and FA series is mentioned in the article you link:

While FA lenses are identical in operation to F lenses, they feature improved electronics that support the MTF program line.

Of the specific lenses you mention, optically they are essentially the same. So the only functional difference will be if you use a shooting mode that uses MTF, namely Green or P mode.

[demp10]

The F series have some of the best budget zoom lenses in the entire Pentax line-up. Plastic on the outside but solidly build with nice balance. The grayish color is also very distinctive. Most of the FA zooms look plasticy and cheap in comparison.

The SMC-F 24-50 F4, SMC-F 35-70 F3.5~4.5 and SMC-F 35-105 F4~5.6 are some of the finest. The last 2 have a very good "macro" mode by twisting the zoom past the long end.

[baro-nite]

So, to be sure, are you saying that the Green button doesn't work (e.g. in Manual mode set shutter speed) with an F but will with an FA?

No, that will still work. I was referring to Green Mode, i.e. turn the exposure mode dial to the green rectangle. That said, it's possible (I'm only guessing) that you would get different values (in some cases) using M mode plus Green Button with an F- versus FA-series lens. MTF program line is the lens telling the camera what aperture values give the highest resolution. If the camera has that info it will use those aperture values when feasible. Lacking that info I suppose (guessing again) that the camera has default shutter and aperture values for a given meter reading.

[boriscleto]

So, to be sure, are you saying that the Green button doesn't work (e.g. in Manual mode set shutter speed) with an F but will with an FA?

Thanks.

MTF Priority is one of the options for setting the Program Line. You can still use Hi-speed priority or Depth-of-field priority with F lenses.

[boriscleto]

The SMC-F 24-50 F4, SMC-F 35-70 F3.5~4.5 and SMC-F 35-105 F4~5.6 are some of the finest. The last 2 have a very good "macro" mode by twisting the zoom past the long end.

You left out the F35-135 F3.5-4.5 and the F70-210 F4-5.6.

I like the 35-135 more than the FA28-105 F4-5.6

https://www.pentaxforums.com/forums/lens-sample-photo-archive/185244-super-mu...3-5-4-5-a.html

https://www.pentaxforums.com/forums/lens-sample-photo-archive/196946-super-mu...-f4-5-6-a.html

[Spodeworld]

Thanks guys....I've never played with the P or Green modes (had though it referred to the Green button) on my K20D so I didn't realize these options existed..... been a bit of an education....

[Docrwm]

I do like the F35-70, the colors are excellent that come out of that little lens.

[audiobomber]

Thanks guys....I've never played with the P or Green modes (had though it referred to the Green button) on my K20D so I didn't realize these options existed..... been a bit of an education....

Green mode sucks because it severely limits your options, but P mode is brilliant. You can choose a Program line that will automatically adjust the settings to what you want to do, and fine tune aperture and shutter speed with the front and rear dials if required.

[snake]

Oddly, I've never seen an FA 50 1.7, nor have I seen an F 50 1.4. If I saw the former, I'd snatch it up. I love my F50 1.7 because the focus is unbelievably fast, plus it's sharp from wide open and doesn't need a lens hood. If I find a cheap f50 1.4, I'd probably pick it up, but noting the fact that it needs a lens hood and like the FA50 1.4, it won't focus as fast as the 1.7

[demp10]

You left out the F35-135 F3.5-4.5 and the F70-210 F4-5.6.

I just included the ones I have and use regularly

I am contemplating to get the F 35-135 and the F 70-210 just to complete the series.

[snostorm]

No, that will still work. I was referring to Green Mode, i.e. turn the exposure mode dial to the green rectangle. That said, it's possible (I'm only guessing) that you would get different values (in some cases) using M mode plus Green Button with an F- versus FA-series lens. MTF program line is the lens telling the camera what aperture values give the highest resolution. If the camera has that info it will use those aperture values when feasible. Lacking that info I suppose (guessing again) that the camera has default shutter and aperture values for a given meter reading.

I don't think there has been any definitive explanation from Pentax on this, but I believe that if the lens transmits no specific MTF information, the camera defaults to somewhere between 1 and 2 stops down from max aperture for a given lens in the MTF Program Line if possible. This made sense to me since most lenses have "sweet spots" within this range. I experimented with this a long time ago and can't remember the exact conclusion I came to, except that it seemed to make enough sense for me to accept their solution. . ..

Scott