[anselesn]

I’m excited to upgrade my older model 55-300 lens to new PLM version based on the reviews I’ve been reading that speak to significantly faster AF.

And I’m wondering whether any other, newer Pentax lenses will also show significantly faster AF on my K-70.

My current lenses are:

DA 55-300 old version
DA 35 F2.8 Ltd. (older non-HD version)
FA 50 1.4
DA 18-135 WR (also older model, I think)

Thanks for your help.

[Adam]

The DA 35mm is a bit slow because it's a macro, so there's not much you can do there. The 50mm should feel nice and quick, as should the 18-135mm. Unfortunately nothing else currently compares to the 55-300mm in terms of AF speed, but I'm sure you'll enjoy it! It covers a really useful zoom range that you can't go wrong with.

If you're looking to upgrade the 18-135mm, the 16-85mm is better optically, but the focusing is the same.

All Pentax lenses are listed here if you're looking to see what's out there:
Pentax Lens Search | PentaxForums.com

[BWG]

The 15, 21, 40and 70are all fast, especially the 40.

[hcc]

The 15, 21, 40and 70are all fast, especially the 40.

+1
The DA Limited pancake lenses are really fast focusing lenses, especially the DA40mm xs IMHO. In addiition, these are nice APS-C lenses with great IQ.

While the DA Ltd pancakes are not cheap, the DA40mm xs is a steal.

Worth to consider IMO.

[anselesn]

Thank you all. These are very helpful.

I’ve been playing lately with a Sony a6300 and what feels like its truly instant focus. I hope your answers will help me stave off that very other temptation. 😀

[pres589]

The 18-135 is quite fast focusing, for my tastes. I wish my recently acquired Sigma 28mm EX would focus like this lens.
DA 50 1.8 and DA 35 2.4 are both fast focusing in my experience.

[TER-OR]

10-17 fisheye! Anything past around 3 feet away is already at infinite focus!

[angerdan]

I’m excited to upgrade my older model 55-300 lens to new PLM version based on the reviews I’ve been reading that speak to significantly faster AF.
And I’m wondering whether any other, newer Pentax lenses will also show significantly faster AF on my K-70.

DA 55-300.........-> 55-300 PLM
DA 35 F2.8 Ltd..-> FA 31 1.8 Ltd.
FA 50 1.4...........-> D FA* 50 1.4 SDM (2018)
DA 18-135 WR.ii-> DA 18-85 DC WR

Other lenses with fast AF for Pentax are:

• Sigma 50-150mm
• Pentax FA* 80-200mm 2.8 with PowerZoom
• Pentax FA* 300mm 4.5

And some lenses even have an AF limiter, increasing the AF speed too.
Lenses for Pentax with focus limiter - PentaxForums.com

[pres589]

I'm surprised to see that the 18-135 isn't fast enough focusing for some folks.

[jddwoods]

I have a 55-300 PLM which I use on my K-3. The only other lenses that seem to be almost as fast focusing are my DA 15, 21 and 40 Limiteds. They may seem almost as fast but they are screwdrive and therefore not silent. I also have the DA 16-85 and the autofocus is fast enough for me but it is not quite as fast as the PLM. What I find amazing with the PLM is despite the slow aperture range it focuses fast and accurate even in dim lighting. I hope we see more PLM lenses in the future.

[Saltwater Images]

The 15, 21, 40and 70are all fast, especially the 40.

What he said. It's one of the reasons I shoot pancake primes. Either macro 35 or 100 is slow. The 15 is fast. The 21/40/70 are blazing fast!

[Rondec]

Lenses with DC motors tend to be pretty fast -- 18-135, 16-85, DFA 24-70/28-105/70-200/15-450. I think the DA 40 is one of the faster primes I've used due to its really short focus throw, I think the DA 15 is pretty fast, although I seldom focus it and usually just shoot it in hyperfocal (it's instantaneous).

[mikesbike]

Short focus throw is apparently one reason for the improved AF speed of the DA 55-300mm PLM lens. A downside can be that a short throw makes MF more difficult to fine tune. I find with my DA 55-300mm HD WR, with its longer focus throw is excellent for MF. At the same time, if I am using it for all subjects being at some longer distance, that makes the throw short anyway, so AF speed is pretty good. The same at nearer distance if focus points of subjects are all within a similar distance from each other. Where it is slow is when going from near to far distance. I like it because unlike the new lens, it is not of internal focus design (which allows the new one to be more compact) therefore it does not suffer focal length loss due to "focus breathing" at lesser distances than infinity focus or close to it. A shot of a bird taken at 30 or 40 feet and 300mm with my older lens will be at true 300 mm, not less.

[SSGGeezer]

+1
The DA Limited pancake lenses are really fast focusing lenses, especially the DA40mm xs IMHO. In addiition, these are nice APS-C lenses with great IQ.

While the DA Ltd pancakes are not cheap, the DA40mm xs is a steal.

Worth to consider IMO.

And its internals are the same so its IQ is amazing! The only down side is that it is sometimes hard to put on and off with my huge sandwich clamps.
The new 55-300 PLM on my K-50 is very quick and accurate in focusing. I was shooting seagulls as they swooped around the beach near me today and ended up with quite a few keepers at various focal lengths. I was happily amazed at how tight the focus was.

[c.perkins]

I have only missed a handful of shots due to not getting focus quick enough.
My opinion of Pentax screw drive is that it works pretty dang good and good enough for me.
Most of my lenses have quick shift so I can manually get into or close to focus and then let the camera/lens do its thing which is a plus.
To be honest, the quickest focus lens in my stable is the Sigma 18~300 and I believe the reason is that it has such a short focus throw.
A lot of photographers do not like the super zooms.
My Sigma is not the sharpest throughout its range but it can surprise you at times.
Very good walk a bout lens.
The brighter it is the better but even in lower light the pictures appeal to me and look like a film shot with some grain which I like.
My signature lists all my lenses.
I am not buying anymore, I am not buying anymore, I am not buying anymore.
Well, that is what I tell myself

Clarence