Very impressive!

Seems like there are more questions than definite answers at the moment on this topic.

I've just been reading a lenghty topic of the same kind on a french pentax forum, the guy who was hesitating between the same lenses' selection eventually went for the 100-300 f4, and seamed very pleased with it's choice, impressed as he was by the sharpness at 300mm wide open.

Thanks Alan,

I can't remember if I tested the lens with or without the UV filter that came with it.

I know I never used it with it previously (it seemed to me to put a slight color cast that I didn't like), so that might explain why I never noticed the spot, if that was indeed the reason.

My K100D's gone for servicing, so I'll have to wait until next year to do some more tests.

Ps: was the fly pic on your profile taken with that lens?

Thanks Daniel,

By concave you mean curving away from the sensor? Difficult to say, looks fairly flat, could be concave or convex, I'll have a closer look tomorrow in natural light.
Just had a look at the adaptall-2 website specs for this lens, looks like it is flat.
What is strange is that I never noticed it before, I didn't use the lens much, maybe never in conditions that favored this kind of results (good thing I don't shoot blank pages for fun! :lol

Hello,

I was checking my Tamron adaptall before putting it up for sale, and I noticed in some of the test pictures a strange bluish spot, relatively large (maybe 1/15th-1/20th of the frame accross), dead in the center of the frame. I hadn't noticed this spot before. The lens looks clean and clear to me, can't see any dust, fungus or haze inside, at least to my naked eye.

I couldn't figure out which parameters/situation made it appear - stopping down made it slightly more defined.

This doesn't happen with other lenses, so I'm thinking it's not the camera (K100D super). It seems to be there mostly when there is a lot of white in the frame (-> overexposure? high contrast?).

Anybody got any idea?

Could it be something to do with the coating? I'd like to know if it's a limitation of this lens or if something's degraded.

Thanks

Thanks guys for the warm welcome!

Hi,

I used to have a Tamron 70-300mm and a Tokina 400m MF with which to cover the long end, and I'd like to invest a bit more money to get better convenience and quality.

Which of these would you recommend if what matters most is quality at the extreme long end:

. Bigma (sharp wide open at 500mm?)

. Sigma 100-300 f4 + Tamron 1,4xTC

. FA*/F*/DA* 300 f4 + Tamron 1,4xTC (is the DA* still significantly more expensive than the 2 older versions?)

TIA

Hi to all,
Just registered, although I've enjoyed reading on this (and other) forum for a while.
I've had a K100D super for almost a year, never had a SLR before, and so still have many many things to learn.
Hope to be able to contribute actively in the future!