[MJTQld]

Hi all
Any anyone tell me the difference between 15 f/4 vs 15 f/3.5

Thanks
MJT

[BigMackCam]

About a third of a stop

Seriously, though, the DA15 f/4 is a modern lens designed for APS-C sensor cameras. It has an awful lot of fans due to its excellent image quality.

The Pentax "K" and "A" 15mm f/3.5 lenses are manual focus models designed for use on full-frame cameras. The later "A" model gets a very high score in our user reviews, while the "K" gets a decent score but not as good.

All three lenses will work on Pentax APS-C models, but only the "K" and "A" 15mm f/3.5 work on full-frame, unless you use crop mode.

[Wild Mark]

About a third of a stop

Seriously, though, the DA15 f/4 is a modern lens designed for APS-C sensor cameras. It has an awful lot of fans due to its excellent image quality.

The Pentax "K" and "A" 15mm f/3.5 lenses are manual focus models designed for use on full-frame cameras. The later "A" model gets a very high score in our user reviews, while the "K" gets a decent score but not as good.

All three lenses will work on Pentax APS-C models, but only the "K" and "A" 15mm f/3.5 work on full-frame, unless you use crop mode.

I have two copies of the K15/3.5 one being the aspherical version the other being the spherical. The A version is also spherical. I do not have the DA.

CONSIDERABLE difference exists between the two versions I have. The aspherical is simply superb, the spherical version is average. I compared the FA20/2.8 with the K15/3.5 aspherical and have formed the view that both are roughly equally within the 20mm FoV (this being on full frame camera).

But, if you are talking about the DA15/4 then clearly you are talking about crop sensors so my immediate suggestion is to disregard the K15/3.5 altogether. The simplest reason is the DA15/4 is 4x less in size and, unless you can get the aspherical version, the DA15/4 will wipe the floor with the older K15/3.5 or even A15/3.5

In summary, the K15/3.5 (aspherical version) is a true collectors lens with very good performance on full frame camera. I would happily take this lens out with my K1 for landscape shoots. But that is where its utility ends in IMHO. On cropped sensors it make no sense to have this lens as the DA15/4 is clearly better on many levels.

FF comparison: k15mm aspherical vs k15mm non-asp vs FA20mm - PentaxForums.com

[Adam]

Excellent summary, @Wild Mark;

Adam
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[h4yn0nnym0u5e]

I have two copies of the K15/3.5 one being the aspherical version the other being the spherical. The A version is also spherical. I do not have the DA.

CONSIDERABLE difference exists between the two versions I have. The aspherical is simply superb, the spherical version is average.

<snip/>

FF comparison: k15mm aspherical vs k15mm non-asp vs FA20mm - PentaxForums.com

I'm still convinced there's something wonky with your copy of the A15/3.5. Mine's pretty sharp, at least around f/8 - see Post your K-1 pics with vintage glasses - Page 3

Cheers

Jonathan

[gm4life]

The 15 Limited F4 is an awesome lens, compact well built and fairly sharp across the entire frame. I really don’t think they come any better than that.