[BarryE]

The obvious difference in specs apart, anyone any view on how these compare ?

I have a 16-50 which I only use in the rain, preferring to shoot with primes when it's dry. I like the results from this lenses but I find it too heavy most times.

I've tended to ignore the 20-40 as it would duplicate my 21 and 40, or would it ? I find I want to shoot more in showery days and therefore the small 20-40 may be preferred to the 16-50.

I can check out the reviews, but they only tell a part of the story, and are subject to batch variations too much. Anyone a hands on view of these two lenses, please ?

Thanks

[Wingincamera]

I can only comment on the 20-40 and can say it is now the default lens that stays on my camera, replacing the 35 macro. For general use for family stuff I usually go for the 18-135 because of the range, but I really like the 20-40.

[aleonx3]

The obvious difference in specs apart, anyone any view on how these compare ?

I have a 16-50 which I only use in the rain, preferring to shoot with primes when it's dry. I like the results from this lenses but I find it too heavy most times.

I've tended to ignore the 20-40 as it would duplicate my 21 and 40, or would it ? I find I want to shoot more in showery days and therefore the small 20-40 may be preferred to the 16-50.

I can check out the reviews, but they only tell a part of the story, and are subject to batch variations too much. Anyone a hands on view of these two lenses, please ?

Thanks

I have both lenses. I feel the same, the 16-50 is quite a bit heavy so I use the 20-40 more.
IMHO, the 20-40 is a unique lens that you have to think of it as a stack of primes, not a zoom lens. Therefore, when I shoot in situations, I pick a focal length and seldom change it unless I find it necessary. There are several (5) focal lengths I usually pick, 20, 23, 30, 34 and 40. For example, the advantage of 23 vs 24 is that the max aperture is 3.2 vs 3.5, likewise for 34 vs 35 it is 3.5 vs 4. The lens is sharp at each focal length wide-open, so you have lots of flexibility and room to tweak the exposure and shutter. Mounting the lens on the k-3 also helps as there is also room for cropping.

Since I bought the 20-40, it pretty much becomes my travel lens. The 16-50 is only used for gigs.

[GaryH]

I had the 16-50 and the 21,40. I chose to sell the 21 and 40 and buy the DA 20-40 for its versatility, weather sealing and much lighter weight than the 16-50. The 20-40 has become my night time lens when we travel instead of a fast prime. It gives a little more speed at 20mm and the versatility of a zoom appeals to me vs my FA31mm. I travel with the 20-40,16-85 and 12-24 and everything is good.

[zeitlos]

I had both for a while. 16-50 stayed.

[UncleVanya]

For example, the advantage of 23 vs 24 is that the max aperture is 3.2 vs 3.5, likewise for 34 vs 35 it is 3.5 vs 4.

Hummm... do you think this is fully accurate? I would expect that the lens focal length to f/stop relationship is less "stepped" and more continuous. I would also expect that the camera is estimating focal length based on feedback from the lens - and that this estimate is not perfect. I would expect that despite the meter saying there is a 1/3 stop difference that the actual difference (based on histogram) is less than 1/3 of a stop and that the actual transmitted light delta is closer to 1/6 of a stop or even less. My point is that I would just frame the thing the way I wanted and not worry about the 1/3 stop difference.

[fredralphfred]

. . . I would expect that the lens focal length to f/stop relationship is less "stepped" and more continuous. I would also expect that the camera is estimating focal length based on feedback from the lens - and that this estimate is not perfect. . .

That's a question I've had for quite a while. I just assumed that there was a cam in there somewhere (or a groove in a tube, etc.) that adjusted the aperture in steps based on focal length. You seem to think that it's actually a linear adjustment, with rounding by the camera's electronics providing the appearance of steps. That makes more sense to me. Does this accurately reflect your opinion?

[Sandy Hancock]

I had both for a while. 16-50 stayed.

Ditto. The extra range, wider aperture at the long end, proper hood and higher level weather sealing of the DA* trumped the size, weight and beauty advantages of the limited.

[UncleVanya]

That's a question I've had for quite a while. I just assumed that there was a cam in there somewhere (or a groove in a tube, etc.) that adjusted the aperture in steps based on focal length. You seem to think that it's actually a linear adjustment, with rounding by the camera's electronics providing the appearance of steps. That makes more sense to me. Does this accurately reflect your opinion?

Yes. See this for more details: Constant vs. Variable Aperture zooms - Digital Grin Photography Forum In non-constant aperture zooms the f/stop (ratio) will go up as your focal length gets longer using the same diameter aperture opening. Constant aperture zooms have additional adjustments to them (see link) to allow them to effectively hold this ratio constant across the lens zoom range.

[fredralphfred]

Yes. See this for more details: Constant vs. Variable Aperture zooms - Digital Grin Photography Forum In non-constant aperture zooms the f/stop (ratio) will go up as your focal length gets longer using the same diameter aperture opening. Constant aperture zooms have additional adjustments to them (see link) to allow them to effectively hold this ratio constant across the lens zoom range.

Wow. I had no idea. THANK YOU for an informative link!

[Nicolas06]

Yes. See this for more details: Constant vs. Variable Aperture zooms - Digital Grin Photography Forum In non-constant aperture zooms the f/stop (ratio) will go up as your focal length gets longer using the same diameter aperture opening. Constant aperture zooms have additional adjustments to them (see link) to allow them to effectively hold this ratio constant across the lens zoom range.

Hum if I understand this right, the DA20-40 would be naively f/2-4 or f/2.8-5.6 to keep the aspect ratio. So even variable apperture zoom do have some corrective elements or the optical formula doesn't allow f/2.

And now that we speak of the f stop displayed, it seem obvious it is just an approximation. There no point to change the actual diaphragm size when going from one focal length to another and I think the eye would suddenly see the difference in light gathering on the view finder.

So I'd really bet there isn't the "great" difference between 34mm and 35mm displayed... Well if we can speak f/3.2 to f/3.5 a great difference... That's look like 1/5 of a stop, nothing really noticable.

[BarryE]

Is there anywhere that defines the difference in weather sealing between the DA* and those lenses marked as WR ?
In this case I'll happily use the 16-50 in the rain, but is the 20-40 going to be happy in a downpour, rather than just a light drop ?

I guess this is an open question on weather resistance as I'm not as confident in my 100 macro as the 16-50. Should I be ?

[Pål Jensen]

The 16-50 is very prone to flare...

[Sandy Hancock]

Is there anywhere that defines the difference in weather sealing between the DA* and those lenses marked as WR ?
In this case I'll happily use the 16-50 in the rain, but is the 20-40 going to be happy in a downpour, rather than just a light drop ?

I guess this is an open question on weather resistance as I'm not as confident in my 100 macro as the 16-50. Should I be ?

The DA* lenses are supposedly weather sealed to a level beyond the other Pentax WR lenses. I haven't tested them formally, but I have shot my DA*50-135 in *torrential* rain and shot it and my DA*16-50 in very bad weather for 12 hours. I am utterly confident in them.

---------- Post added 16-07-15 at 08:57 PM ----------

The 16-50 is very prone to flare...

Define "very". I got some pretty nasty flare with my HD DA20-40.

[Nicolas06]

Define "very". I got some pretty nasty flare with my HD DA20-40.

And if I'am not mistaken, the DA20-40 is rather resistant, isn't it?