[MJKoski]

Question to D-FA 15-30 users: Do you find your lens to be usable wide open in 20-30mm range? Mine is excellent at 15mm but cannot say the same for 20mm or 30mm setting after shooting few aurora scenes tonight. 30mm needed stopping to f/5.6 at least to be somewhat usable towards the edges. 20mm needed something between f/4 - f/5.6 to be of any use.

This is somewhat disappointing as Irix 15mm would probably be as good as the Penron at 15mm with 33% the cost. Zeiss 28/2 stopped to f/4 walks over the zoom and I expect the new Samyang 20/1.8 to be supreme choice as well.

[howieb101]

Hi.

Well, the new Pentax lens while very good is still a zoom and as such will always be a comprise lens.

If it doesn't meet your needs you may have to go down the prime path. However, I would think the new zoom probably is weakest if your use case is astrophotography as you want it sharp at f2.8.

For other typical landscape use you should be stopped down to F8-11 territory.

Howie Be

[MJKoski]

15mm is very usable at f/2.8. However, the other end of the zoom range feels a bit off. Not sure it should perform that way. Tamron 15-30 reviews are giving it good marks between 20-30mm as well.

[Paul the Sunman]

Have you tested it for front or back focus?

[biz-engineer]

Question to D-FA 15-30 users: Do you find your lens to be usable wide open in 20-30mm range?

This maybe a problem of your copy, because mine if sharp from 15 to 30 and wide open... which make me wonder why some people still need a Zeiss 21 prime.

[kiwi_jono]

I would check focus adjustment (with a calibration chart). If the focus was out a little bit then 15mm would look better than 30mm due to difference in depth of field.

[Na Horuk]

This is somewhat disappointing as Irix 15mm would probably be as good as the Penron at 15mm with 33% the cost. Zeiss 28/2 stopped to f/4 walks over the zoom and I expect the new Samyang 20/1.8 to be supreme choice as well.

Sure, and the Samyang 14mm f2.8, Samyang 24mm f1.4, Pentax F 28mm, Zeiss 25mm,.. but those are all primes. They should have some advantages over a zoom lens - size, overall optical quality, aperture. If none of those, then at least price should be much lower. Still, I don't own a DFA 15-30mm, but I have seen some really nice sample photos. I mostly shoot wide angle with primes, but this lens is really tempting me to try a zoom, as it shows that zooms have come a long way.
I would recommend you check the lens for fingerprints or dirt, especially the back element. Check the lens for back/front focus. Make sure the distance scales are not miscalibrated, if you are planning on using those (for astrophoto and night time landscapes, you kind of have to rely on these). Make sure you are not using UV filters and make sure you are using the lens hood. Finally, make sure the lens does not suffer from decentering. There are numerous threads about this. It is an issue that is most commonly a problem with UWA lenses. Take some test photos wide open of a subject near the minimum focus distance, something like a book or newspaper placed 45 degrees to the camera sensor. It has to be further than the MFD, but not very far. Shoot Av mode, wide open aperture, 2 sec timer, low ISO, hopefully in good, bright natural light, and use Live view with Focus peaking to manually focus. Then compare the result, check the DoF and sharpness.
Feel free to upload samples from your lens in this thread, hopefully with intact exif data and 100& crops

[MJKoski]

I do not use autofocus. Only manually focus with live view to achieve pinpoint stars in the corners. This is infinity focus case.

biz-engineer, mind sharing some examples wide open @ infinity focus? I will do the same after getting back home later tonight. This lens was so damn expensive that it must perform or it is going back.

[Na Horuk]

Only manually focus with live view to achieve pinpoint stars in the corners. This is infinity focus case.

A couple points about this.
First, the DoF is not parallel to the sensor, but it is often curved. So getting focus in edges does not mean the whole photo will be well-focused.
Secondly, the live view focus peaking often shows the wrong DoF, especially with UWA lenses near infinity focus. My Samyang 14mm can be focused with focus peaking, but only the first 1m. Beyond that, the peaking is useless as it shows a way bigger DoF than the final photo will actually have.
Third, Live view often stops down the lens. Live view rarely uses the lens wide open, which means if you shoot wide open, the DoF will be deminished in the actual photo. Basically, you are focusing at f4 and then take the photo at f2.8, which leads to misfocusing. This is why I said you should figure out actual infinity by looking at the focusing scales. Take photos, wide open in bright daylight, and remember what the label was for those photos. Then check them on computer at 100%, see which one is actually focused to infinity and remember that focus scale label. If the lens is not parfocal, you need to do that for the different focal lengths as well. This way you can then quickly focus to the correct infinity, on your specific camera and lens (due to factory tolerances there can be variation and one lens might be misfocusing on one camera, but not another), even in near complete darkness.

[MJKoski]

Excuse me, live view shows just what it shows wide open. I had Tamron 15-30 with D810 and it worked just like that and so does this lens. Tamron 15-30 field curvature is minimal. Zeiss lenses, Loxia and 21mm DSLR distagon however are examples of wonky field curvature wide open.

If K-1 does not drive lens wide open in live view in darkness when set to f/2.8 then the design is severely screwed up. There are no excuses in there.

Let's think about something - the price & performance

I will directly compare this lens to:

-Nikkor 14-24 of which I owned three copies. It is cheaper but works better wide open thru the focal length range. Has focus shift issues
-Zeiss 21mm DSLR Distagon, had 4 copies of this lens during the last 7 years. It is cheaper and destroys the Tamron @ 21mm
-Zeiss Loxia 21mm. Had one perfect copy. It is cheaper and puts 21mm DSLR Distagon to shame
-Canon 17mm TS-E. A little more pricier but usable wide open unshifted/tilted. Stopped down it outperforms everything in this list

Tamron is the 2nd expensive option on that list but my copy performs only @ 15mm.

[beholder3]

Reliable tests show the Tamron outperforms the Nikkor which by itself seriously outperforms the Canon T/S (see Canon TS-E 17mm f/4 L - Analysis - conventional setup, Nikkor AF-S 14-24mm f/2.8G ED (FX) - Review / Test Report - Analysis).

The Zeiss lacks autofocus, has zero Zoom capability and is not better than the Tamron at the one focal length it offers:
Zeiss 21mm f/2.8 Classic Lens Image Quality

Just some facts to consider.

[MJKoski]

What facts? Owning all those lenses and the Tamron only thing it excels is 15mm focal length. Photozone tests are completely unusable in real world due to shooting test targets at close distances. Or some brick walls and trees in digital picture case. They have nothing to do with landscape infinity focus range.

Asking over 2x the price of Tamron 15-30 for Penron 15-30 is hilarious. I asked for owners experiences because I think it should perform better in 20-30mm range.

[beholder3]

I always wonder why some people have to make such a religion out of their little personal opinion ("I know the TRUTH") and defend it against solid arguments with such a level of hate coupled with a sad low level of own arguments (in a photoforum well made own comparison shots of the same subject with same parameters are the minimum standard).
Being a diehard fan of one's own opinion is not nearly enough.
It must be possible to add arguments and criticize poorly made claims.

[Na Horuk]

Well then it looks like you already know everything. Maybe try the Sigma 18-35mm f1.8, but check the many threads about its AF. Or a Samyang - Im a fan of the 14mm, but 24mm and 20mm both sound good and are FF compatible as well.

Excuse me, live view shows just what it shows wide open

Yes, it shows what it does. And that, which it shows, is often inaccurate. With mirror lenses, slow aperture lenses, some low contrast telephoto lenses, and ultra wide angle lenses. Feel free to read up on threads about this or do tests yourself. The Focus peaking has a certain algorithm, which is great for some lenses, and not so great with other lenses. Also, Nikon and Sony and other brands have different implementations of Focus peaking, and I cannot know whether it is any better or worse than Pentax. Since Sony puts so much emphasis on mirrorless cameras, I would assume they developed FP more than Pentax did.

The stopping down in live view is not an excuse, but it is a fact. It might not be a problem in dark conditions, but it is a camera behaviour that the photographer should be aware of. You should use Digital zoom along with focus peaking in live view, as the Digital zoom feature opens the lens aperture to maximum.

Meanwhile, you can check sample photos of the DFA 15-30mm posted by other users here: https://www.pentaxforums.com/forums/samplesearch.php
https://www.pentaxforums.com/lensreviews/hd-pentax-d-fa-15-30mm-f28-ed-sdm-wr.html
Seems to be getting some mixed reviews. Might be your copy of the lens has some problem, which is what I already mentioned in my earlier post. Checking for simple problems can be the easiest way to find out whether the lens is behaving as intended or not. And if you do this while its still in warranty, you can get it exchanged or repaired

[MJKoski]

I do not use focus peaking either. It does not hit anything reliably. Neither it did with Sony.

Sony A7x bodies stop some lenses down in liveview to compensate for focus shift. Tamron 15-30 has none. There is no logic explanation of why it should not be wide open when set to wide open in live view when conditions are dark.

Only reliable and honest IQ evalutions are currently delivered by Lloyd Chambers of currently available review sites. Photozone et all. shoots test targets at close distances which are not real use cases and do not show anything about optical quality when shooting out there.

Again, I asked for owners opinions on this matter. Not some worthless brick wall tests.