[kypfer]

My "Bigma" seems to be getting intermittent, so I'm considering replacement options.

Question :- Can one operate the zoom on the Pentax 150-450mm by "tromboning" the front of the lens, like I can with my Sigma, or does one have to operate the zoom using the control ring?

When dealing with birds in flight, especially in blustery conditions, I find it so much easier to zoom out, find the subject and achieve preliminary focus, then zoom in simply by pushing the front of the lens whilst maintaining focus with a half-push of the shutter button.
It's a technique that was promoted by Tamron in the days of manual focus one-touch zooms and a technique I've relied on since.

[pschlute]

No. But the zoom ring is the larger of the two and is at the front

[derekkite]

To travel the full zoom, it is a quarter turn on the ring.

[kypfer]

No. But the zoom ring is the larger of the two and is at the front

Thanks … not what I wanted to hear
My Sigma has a similar layout, but I can operate the zoom from in front of the ring without twisting my grip thereby maintaining support for the lens.
Trying to operate a zoom ring in windy conditions really isn't an option (for me) with a big lens, I just don't manage to hold the whole thing steady enough to be useful.

---------- Post added 08-23-21 at 07:24 AM ----------

To travel the full zoom, it is a quarter turn on the ring.

Much the same as my Sigma

[steephill]

Maybe, it depends on how much zoom creep each lens has. Some report none and others complain about how much it creeps. Mine creeps and I can trombone zoom in the manner you describe but frankly I find it easier to just turn the zoom ring.

[C_Jones]

I just use the ring on my Sigma 150-500 for distance focus adjustment (field of view layout).

[cmohr]

It is possible, as some have said, different lenses have different amounts of zoom creep, but, I would not suggest doing it with any lens, as you are forcing the zoom mechanism to work in an unintended manner. IE: the zoom ring, and it's helicoid is made to drive the extension of the zoom, not the other way around.

[kypfer]

I just use the ring on my Sigma 150-500 for distance focus adjustment (field of view layout).

Fine on a nice day with a static subject, maybe on a tripod or resting on the shelf in a hide … try it on top of a cliff in a Force 4 with the bird bouncing up and down faster than it's going forwards … finding the subject in the viewfinder in the first place can be an achievement, keeping it there whilst I zoom in and the camera focuses, that's where the good grip comes into play

[disasterfilm]

Something else to consider is the amount of reports we've had recently of the 150-450 separating at the zoom element and needing massive repairs to get functional again. Some folks have had theirs fall apart as they lift it out of their bag.

Hate to say this, but it's 100% changed the way I handle that lens. It's kid gloves all the time with the 150-450. For that reason alone I'd dissuade the trombone slide gliss with this one.

[kypfer]

Something else to consider is the amount of reports we've had recently of the 150-450 separating at the zoom element and needing massive repairs to get functional again. Some folks have had theirs fall apart as they lift it out of their bag.

Hate to say this, but it's 100% changed the way I handle that lens. It's kid gloves all the time with the 150-450. For that reason alone I'd dissuade the trombone slide gliss with this one.

Valued response … vey many thanks … if my "Bigma" finally does go the way of all good things (assuming the problems are the lens and not the camera) I'll be looking for another one!

[MDW_uk]

Kypfer,

If you want some comparative information, I own both lenses - had the Sigma 150-500 for about 3 years and then had a rush of blood to the head and bought the Pentax 150-450, which I've also had for about 3 years (both from new):



The Pentax is heavier, and obviously loses 50mm in max focal length, but it has weather-resistance unlike the Sigma.

The Sigma tripod foot is longer, more centrally positioned along the length off the lens and has finger-grip grooves, which makes it easier and more comfortable to carry the camera/lens combination by the tripod foot than with the Pentax.

The Sigma focus lock is fiddly to use; I often found it unlocked when I thought I had locked it, but never had that problem with the Pentax.

The zoom rings work in opposite directions - one is clockwise the other anti-clockwise (not a problem if you stick to one brand of lenses, but if you don't it's easy to find yourself turning it the wrong way).

The Sigma is discontinued (replaced by the 150-600, which is not available in Pentax mount), the Pentax is still current.
The Sigma has the option of 2 in-lens stabilisation modes (although it's not recommended to use in-lens OS that and Pentax in-body OS at the same time).

There are other differences, like the half-stop max aperture, focus range limiter and preset modes on the Pentax, but I don't recall them all (don't have the Sigma with me as I write this)


I've never deliberately used the zoom in the way you described, but I've just checked with my copy of the Pentax, and it's possible to do it (though how easy it is will depend on the stiffness of the zoom).

The Sigma is reputed to be "soft" at full zoom, which is the main reason I bought the Pentax, which was intended as a replacement. However, when I took comparative shots to see which was sharper, I couldn't see any difference at 450mm, so concluded that any drop-off with the Sigma is probably in that last 50mm at the long end.

Although the Sigma is nicer in some ways (lighter, easier to hand hold, more comfortable to carry, OS options), personally I prefer the Pentax overall and have ended up using it every time I need a long zoom. I won't tempt the wrath of others on the forum by saying the 150-450 is better - it's just my preference, and I'm sure others will be happier with the Sigma150-500; I must get round to selling mine!

[kypfer]

Kypfer,
If you want some comparative information, I own both lenses - had the Sigma 150-500 for about 3 years and then had a rush of blood to the head and bought the Pentax 150-450, which I've also had for about 3 years (both from new):

Many thanks for the direct comparisons, this sort of information can be difficult to get … how many others have actually used BOTH lenses, let alone still own both?

[Grokh]

Many thanks for the direct comparisons, this sort of information can be difficult to get … how many others have actually used BOTH lenses, let alone still own both?

Some time ago I had Bigma and 150-450 at the same time. It is necessary to look for frames of comparison.