Tamron 31A (200-500 5.6) vs Pentax 150-450 4.5-5.6

Started Jul 24, 2022 | Questions thread
kypfer Senior Member • Posts: 1,068
Re: Tamron 31A (200-500 5.6) vs Pentax 150-450 4.5-5.6

gkreth wrote:

Hi, everyone!

I have dreamed on and off about getting a Pentax 150-450 f/4.5-5.6, mostly for birding and wildlife.

But it's expensive. Really, really expensive. (For me, anyway.)

I bought a Sigma 50-500 many years ago, and I was disappointed; it seemed very soft at the long end (I know most zooms are softer at the long end, but this copy was just too soft to be acceptable). It also had, well, kinda lousy contrast.

I was wondering about the old Tamron Adaptall 200-500 f/5.6.
I realize that it is MF.
But, it's also, like, one-fifth the price of the Pentax 150-450.

There aren't a whole lotta review on the Tamron, but what I have read seems to indicate that it is pretty sharp, even wide open.

Anyone here ever shoot with one?
Did you like the results?

Oh, I would be shooting this with a K3, and probably with a straight PK adapter. (I have a PKA, but TBH, it's kinda fiddly with the electronic contacts to the body.) I'll probably be shooting it wide open for the most part, because, well, at f/5.6 and where/when I'll be shooting, I don't think I'll be able to stop down much if at all.

Thanks for your opinions, comments, and advice!

My Tamron 200-500mm is the earlier f/6.9 … it's fine on a tripod but not really ergonomically suited to hand-held work.

My Sigma 150-500mm is superior in virtually every respect and is my "go-to lens" for general "birding and wildlife". Personal experience, along with on-line recommendations, suggest the in-lens stabilisation is superior to the in-camera Shake Reduction, especially at the longer lengths, but you do need to give it a second or so to steady itself, on occasion.

I've used Tamron Adaptall-2 lenses since the '70's. My 90mm macro has followed me through four changes of mount and is permanently in my bag. The only reason(s) the PKA mount can be "kinda fiddly", in my experience, is that if it's in need of cleaning and/or lubrication, (all of the rotating "bits and pieces" need to be free in respect to each other) and/or the mount is being fitted incorrectly. The lens aperture needs to be set wide open, the mount aligned and fitted, then the aperture ring set to AE using the little button for the purpose. Do note, there is a drop of sealing varnish on some PKA mounts just clockwise from the electrical contacts, about at the "6 o'clock" position. This can/will interfere with the communication to the camera and needs to be scraped off for reliable operation. This is because the PKA mount was designed before a/f was available and there were only a total of six connection points, including 'ground'. The drop of varnish coincides unfortunately with the seventh contact, that was introduced with a/f cameras, that is required and needs to be grounded for successful "catch-in-focus" operation with m/f lenses.

I'd have no reservations about using a Tamron SP lens if that was all that was available, they were of superior quality in their day, and the f/5.6 aperture should make confirming focus quite easy, even giving scope for a 1.4x teleconverter in good light, but, given a choice, on one of my 24mpixel bodies, the Sigma every time

Hope this helps.

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