[wombat2go]

as long as you don't really need modern coatings, of course.

Here is my DA 18~55 into the sun:
https://app.box.com/s/xnir6j5sp99sdf05g6vs

Compare the 36 year old SMC Pentax -M 1:2 50mm kit lens:
https://app.box.com/s/izcv2q8akxhdh1ajxwuk

[reh321]

I can't speak to "M" lenses {the only one I have is a 50mm f/2, which was not "terrific"}, but the "A" 50mm f/1.7 that was kitted with my Super Program may be the sharpest lens I own .... as you don't really need modern coatings, of course.

....
Compare the 36 year old SMC Pentax-M 1:2 50mm kit lens:https://app.box.com/s/izcv2q8akxhdh1ajxwuk

That sounds exactly like the lens I described as being 'not "terrific" '

[stevebrot]

I'm guessing that some of the old "M" lenses are also quite good.

My guess that "most" of the M-series primes are quite good to excellent and that the rest are merely very good. The bar for optical quality was set quite high in the late 70s when the M-series came to market and Pentax was a prestige brand.


Steve

[stevebrot]

Here is my DA 18~55 into the sun:
https://app.box.com/s/xnir6j5sp99sdf05g6vs

Compare the 36 year old SMC Pentax -M 1:2 50mm kit lens:
https://app.box.com/s/izcv2q8akxhdh1ajxwuk

Much is made of modern coatings and there is no doubt they have improved, but I have found that all of the lenses on my shelf (recent included) benefit from use of a hood and that all exhibit objectionable veiling flare from bright oblique light from out of frame. I have never found the SMC coatings on my 80's vintage lenses to be deficient or a matter for concern.


Steve

[stevebrot]

That sounds exactly like the lens I described as being 'not "terrific" '

You are correct. Your M 50/2.0 is "not terrific". Both it and the A-series equivalent are quite possibly the least capable normal lenses to wear the Pentax or Asahi badge. That does not mean they are bad, just that they are not worth buying used if other alternatives are available.


Steve

[lakeshore]

Some of the old -M lenses in my collection here had slow aperture stop-down due to old lubrication problems.
That can cause inconsistent exposure.
To check, hold the stop down lever open with a fingernail and let the lever suddenly free.
The aperture should stop down instantly with audible "clack".
If if closes visibly slowly or the aperture blades can be seen moving near smallest f/- , or without a "clack", it may need service.

Edit: Forgot to mention to set minimum aperture (f/16 ~22 etc) before doing the above check.

As I said in a previous post in this thread, two of my lenses have "sticky" aperture blades. I have just had my K-50 aperture block problem repaired and I am concerned about damaging or stressing my camera by using these lenses with the green button stop down method.

Is there some way to use my M series lenses, sticky and non-sticky, so as not to stress my camera's mechanism needlessly?

[GUB]

Yes - unmount them by 7 -9 mm then the aperture lever doesn't contact the camera and they work like M42 lenses in AV mode. I drill a small hole for the locator pin at this point and they sit on the camera quite securely.
Another point -- old timers know this but it is under emphasised to newer dslr users is that the eyepiece of the camera has to be covered when metering otherwise light pours in stuffing up the metering. So if you are like me and have a habit of holding the camera away from your face while looking for the green button then cover the eyepiece with your thumb.

[lakeshore]

Does using the green button stop down metering with M series lenses actually strain the camera's mechanism's or is the camera built to handle this type of use without damage?

If the answer to the first part is yes, then I can see myself using DA lenses almost exclusively in order to protect my camera from damage.