Is distortion normal - Pentax HD PENTAX-D FA 15-30mm f/2.8 ED SDM WR Lens ?

**frankoz** · 09-03-2017, 01:01 AM

Hi Folks,

I have just purchased the above lens ahead of a trip to California and Yosemite National park, in particular.

First shots on my K1 have been a little lack lustre wide open at 15mm, although it is probably me needing to get used to the lens. Stopped down to f9, the sharpness improves, but I am finding significant distortion (see attached link) which even Lightroom 6 with the appropriate lens adjustment doesn't fix.

Dropbox - DFA 15-30

Am I to expect such distortion at wide angle or do I have a problem lens? If the distortion is normal, are there any tricks to correcting it; for a AUD1,500 lens, it is a little disappointing.

Thanks for your help

rgds,
John S

Unregistered User 8 · 09-03-2017, 01:19 AM

Hi John. I have just read the in-depth review, and at 15mm it is quite a lot. Here is the link for you to read. Hopefully the others can chime in with a PP fix for you. Good luck.

HD Pentax-D FA 15-30mm F2.8 ED SDM WR Review - Introduction | PentaxForums.com Reviews

Na Horuk · 09-03-2017, 04:53 AM - **1 Like**

Originally posted by frankoz

Am I to expect such distortion at wide angle or do I have a problem lens?

Have you ever used other ultra wide angle lenses?
Come on, it is 15mm and f2.8, you should expect some distortion.

It is very doubtful that your copy has more distortion than it should have, but feel free to compare to the review and user reviews:
HD Pentax-D FA 15-30mm F2.8 Announced - Pentax Announcements | PentaxForums.com
HD Pentax-D FA 15-30mm F2.8 ED SDM WR Reviews - D FA Zoom Lenses - Pentax Lens Reviews & Lens Database
Pentax Camera & Lens Sample Photo Search Engine - PentaxForums.com

Of course, distortion is something that can be really exaggerated or minimized with perspective. Keep the camera level and straight and the distortion will not be as noticeable

However, read up on decentering. This is an issue that is more common with ultra wide lenses. It is not the same as distortion, but it can affect image quality. I have not read many cases of this being a problem with DFA 15-30mm, but check it out. The easiest test is to check if the corners or edges of the photo have consistent quality. If one half of the photo or one corner just never gets sharp, then decentering might be an issue there. But you have to do tests. In good daylight, Av mode, near minimum focus distance, place newspapers to cover frame, right on the focus line, then check the frame for quality. DoF will be shallow, and DoF is usually curved, not flat (so if you focus on a brick wall in the centre, the edges will likely be out of focus, this is normal)

thazooo · 09-03-2017, 05:52 AM

Yes they do show distortion on the wide end, especially on full frame vs. aps-c. APS_C crops the corners.
When I want that Wide Vista look I use a normal focal length lens, shoot Portrait, and create a Panorama.
A good Pano program will stitch it quickly and output a Wide view without the distortions.

Sandy Hancock · 09-03-2017, 05:57 AM - **2 Likes**

Hi Frank. I recognised those shots as being from Glenelg even before I looked at your details

15mm is bloody wide for a rectilinear full frame lens. Distortion at the peripheries is par for the course, and for f/2.8 the sharpness looks excellent. Your images look entirely as expected to me. You will struggle to find a better ultra-wide in the Pentax ecosystem.

One thing to look out for: at intermediate shutter speeds (1/60 to 1/250), shutter shock can cause the SR mechanism to introduce some paradoxical motion artefact. Unless the shutter speed is really low I get better hand held results with this lens when SR is turned OFF. Check it on a tripod.

**pentageek** · 09-03-2017, 06:33 AM

I use DA 12-24, which at wide end shows similar distortion. As Sandy mentioned, 15mm (on FF) is really wide, and visible distortion is unavoidable.

**savoche** · 09-03-2017, 06:45 AM

Looks perfectly normal to me. I don't have the 15-30, but I have a 10-20 that pretty much looks the same (although not as sharp) on APS-C. It just takes some time getting used to and figuring out what to do and not do to get good results. Keeping your camera straight and the focal plane as parallel to the subject as possible help minimise the distortions.

**frankoz** · 09-03-2017, 07:43 AM

Thanks so much to all who have replied. I will read up a bit more.
I have had experience with the DA 10-17mm and love the fisheye effect. On the K1 its good from about 14mm but not as sharp as the 15-30, nor as bright obviously. I will check out decentering also.

---------- Post added 4th Sep 2017 at 12:15 AM ----------

I also need to test corner sharpness a little more

---------- Post added 4th Sep 2017 at 12:23 AM ----------

Originally posted by Sandy Hancock

Hi Frank. I recognised those shots as being from Glenelg even before I looked at your details

15mm is bloody wide for a rectilinear full frame lens. Distortion at the peripheries is par for the course, and for f/2.8 the sharpness looks excellent. Your images look entirely as expected to me. You will struggle to find a better ultra-wide in the Pentax ecosystem.

One thing to look out for: at intermediate shutter speeds (1/60 to 1/250), shutter shock can cause the SR mechanism to introduce some paradoxical motion artefact. Unless the shutter speed is really low I get better hand held results with this lens when SR is turned OFF. Check it on a tripod.

Hi Sandy,

Thanks for the reply; glad to see a local Pentax user. There are a few of us.

You obviously know the Bay fairly well.

I had read about shutter shock and will try mirror up and SR off on tripod.

I guess from a distortion point of view, I have the DA 10-17mm which I used a lot on my K3. I expect distortion on this lens but have been surprised how well LR6 takes care of it, even at 10mm.

I don't know what I expected but for the money, the distortion is more than I bargained for. LR6 is not doing much in correction.

Anyway, thanks for your comments; I will let you know how I go in Yosemite.

Rgds,
John

Bad Boy · 09-03-2017, 08:38 AM

I find this distortion can add to the creativity of a photo. Some times it does not. Then there are tilt / shift software programs that can correct this distortion. As you can see wide angle lenses make vertical elements in architectural photography lean. More so if the camera is aimed up or down. I have used a free program call ShiftN to straighten the vertical elements. Some of the picture will be cropped when using this so compose your images a bit wide.

aurele · 09-03-2017, 09:21 AM

It's more the "wide angle" PoV rather than the distortion that's obvious. The distortion is rather low IMO.

lytrytyr · 09-03-2017, 11:09 AM

Originally posted by frankoz

I am finding significant distortion (see attached link) which even Lightroom 6 with the appropriate lens adjustment doesn't fix.

Can you do a custom correction of the geometric distortion instead?

I've had problems with the automatic vignetting correction of my DA 20-40 at the long end,
and have found that I can do better manually with the custom correction (in Photoshop).

As it happens, I was just watching Nolan's "Interstellar",
and I couldn't help noticing the geometric distortion
on the wide-angle shots of the interior of the farmhouse.
So if you can't get the corrections done,
just pretend that it's for artistic effect!

**mikesbike** · 09-03-2017, 03:17 PM

The tested linear distortion is quite high, but to be expected from a zoom lens going this wide. Of your three examples, however, the one on the right appears to exhibit perspective distortion, which even with a low-linear-distortion WA lens is going to occur under certain circumstances, angles, etc. Even with this degree of linear distortion, it is not generally visible in most shots, such as nature scenes, but can be visible where there are straight lines involved, causing the lines to appear curved.

Sandy Hancock · 09-03-2017, 03:28 PM

Comparing a fisheye to a rectilinear UWA is not really fair - it is precisely the *lack* of barrel distortion of the latter that produces the wild corners. Use it creatively as others have pointed out.

rawr · 09-03-2017, 04:44 PM

Judging from the reviews of the Tamron 15-30, distortion at 15mm is there, but tolerable. On par with other ultra-wide zooms.

(from the lenstip review of Tamron 15-30)

It will have some impact on corner sharpness though, particularly wide open.

**clackers** · 09-03-2017, 06:00 PM

You must not have much experience of ultra wides on full frame, Frank?

Looking at DXO, the mighty Nikon 14-24mm f2.8 has similar distortion. Less at 15mm, but more vignetting as a tradeoff.

The dedicated Samyang 14mm prime has similar distortion.

So, it's par for the course, your technique and framing will need to be up to shooting UWA.

Use the horizontal/vertical level lines in the viewfinder!

09-03-2017, 01:01 AM	#1
frankoz Site Supporter Join Date: May 2011 Location: Glenelg North, South Australia Posts: 127	Is distortion normal - Pentax HD PENTAX-D FA 15-30mm f/2.8 ED SDM WR Lens ? Hi Folks, I have just purchased the above lens ahead of a trip to California and Yosemite National park, in particular. First shots on my K1 have been a little lack lustre wide open at 15mm, although it is probably me needing to get used to the lens. Stopped down to f9, the sharpness improves, but I am finding significant distortion (see attached link) which even Lightroom 6 with the appropriate lens adjustment doesn't fix. Dropbox - DFA 15-30 Am I to expect such distortion at wide angle or do I have a problem lens? If the distortion is normal, are there any tricks to correcting it; for a AUD1,500 lens, it is a little disappointing. Thanks for your help rgds, John S

09-03-2017, 03:17 PM	#12
mikesbike Site Supporter Join Date: Dec 2016 Location: Southeastern Michigan Posts: 4,549	The tested linear distortion is quite high, but to be expected from a zoom lens going this wide. Of your three examples, however, the one on the right appears to exhibit perspective distortion, which even with a low-linear-distortion WA lens is going to occur under certain circumstances, angles, etc. Even with this degree of linear distortion, it is not generally visible in most shots, such as nature scenes, but can be visible where there are straight lines involved, causing the lines to appear curved. Last edited by mikesbike; 09-04-2017 at 10:24 AM.

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09-03-2017, 01:19 AM	#2
Unregistered User 8 Closed Account Join Date: Mar 2015 Photos: Gallery Posts: 8,694	Hi John. I have just read the in-depth review, and at 15mm it is quite a lot. Here is the link for you to read. Hopefully the others can chime in with a PP fix for you. Good luck. HD Pentax-D FA 15-30mm F2.8 ED SDM WR Review - Introduction \| PentaxForums.com Reviews

09-03-2017, 04:53 AM - 1 Like	#3
Na Horuk Veteran Member Join Date: Feb 2012 Location: Slovenia, probably Photos: Gallery \| Albums Posts: 11,186	Originally posted by frankoz Am I to expect such distortion at wide angle or do I have a problem lens? Have you ever used other ultra wide angle lenses? Come on, it is 15mm and f2.8, you should expect some distortion. It is very doubtful that your copy has more distortion than it should have, but feel free to compare to the review and user reviews: HD Pentax-D FA 15-30mm F2.8 Announced - Pentax Announcements \| PentaxForums.com HD Pentax-D FA 15-30mm F2.8 ED SDM WR Reviews - D FA Zoom Lenses - Pentax Lens Reviews & Lens Database Pentax Camera & Lens Sample Photo Search Engine - PentaxForums.com Of course, distortion is something that can be really exaggerated or minimized with perspective. Keep the camera level and straight and the distortion will not be as noticeable However, read up on decentering. This is an issue that is more common with ultra wide lenses. It is not the same as distortion, but it can affect image quality. I have not read many cases of this being a problem with DFA 15-30mm, but check it out. The easiest test is to check if the corners or edges of the photo have consistent quality. If one half of the photo or one corner just never gets sharp, then decentering might be an issue there. But you have to do tests. In good daylight, Av mode, near minimum focus distance, place newspapers to cover frame, right on the focus line, then check the frame for quality. DoF will be shallow, and DoF is usually curved, not flat (so if you focus on a brick wall in the centre, the edges will likely be out of focus, this is normal)

09-03-2017, 05:52 AM	#4
thazooo Pentaxian Join Date: Sep 2006 Location: Mississippi, USA Photos: Gallery Posts: 854	Yes they do show distortion on the wide end, especially on full frame vs. aps-c. APS_C crops the corners. When I want that Wide Vista look I use a normal focal length lens, shoot Portrait, and create a Panorama. A good Pano program will stitch it quickly and output a Wide view without the distortions.

09-03-2017, 05:57 AM - 2 Likes	#5
Sandy Hancock Moderator Site Supporter Join Date: Feb 2012 Location: Adelaide Hills, South Australia Photos: Gallery \| Albums Posts: 11,272	Hi Frank. I recognised those shots as being from Glenelg even before I looked at your details 15mm is bloody wide for a rectilinear full frame lens. Distortion at the peripheries is par for the course, and for f/2.8 the sharpness looks excellent. Your images look entirely as expected to me. You will struggle to find a better ultra-wide in the Pentax ecosystem. One thing to look out for: at intermediate shutter speeds (1/60 to 1/250), shutter shock can cause the SR mechanism to introduce some paradoxical motion artefact. Unless the shutter speed is really low I get better hand held results with this lens when SR is turned OFF. Check it on a tripod.

09-03-2017, 06:33 AM	#6
pentageek Site Supporter Join Date: Jan 2016 Posts: 420	I use DA 12-24, which at wide end shows similar distortion. As Sandy mentioned, 15mm (on FF) is really wide, and visible distortion is unavoidable.

09-03-2017, 06:45 AM	#7
savoche Master of the obvious Join Date: Jun 2011 Location: Lowlands of Norway Posts: 18,311	Looks perfectly normal to me. I don't have the 15-30, but I have a 10-20 that pretty much looks the same (although not as sharp) on APS-C. It just takes some time getting used to and figuring out what to do and not do to get good results. Keeping your camera straight and the focal plane as parallel to the subject as possible help minimise the distortions.

09-03-2017, 07:43 AM	#8
frankoz Site Supporter Join Date: May 2011 Location: Glenelg North, South Australia Posts: 127 Original Poster	Thanks so much to all who have replied. I will read up a bit more. I have had experience with the DA 10-17mm and love the fisheye effect. On the K1 its good from about 14mm but not as sharp as the 15-30, nor as bright obviously. I will check out decentering also. ---------- Post added 4th Sep 2017 at 12:15 AM ---------- I also need to test corner sharpness a little more ---------- Post added 4th Sep 2017 at 12:23 AM ---------- Originally posted by Sandy Hancock Hi Frank. I recognised those shots as being from Glenelg even before I looked at your details 15mm is bloody wide for a rectilinear full frame lens. Distortion at the peripheries is par for the course, and for f/2.8 the sharpness looks excellent. Your images look entirely as expected to me. You will struggle to find a better ultra-wide in the Pentax ecosystem. One thing to look out for: at intermediate shutter speeds (1/60 to 1/250), shutter shock can cause the SR mechanism to introduce some paradoxical motion artefact. Unless the shutter speed is really low I get better hand held results with this lens when SR is turned OFF. Check it on a tripod. Hi Sandy, Thanks for the reply; glad to see a local Pentax user. There are a few of us. You obviously know the Bay fairly well. I had read about shutter shock and will try mirror up and SR off on tripod. I guess from a distortion point of view, I have the DA 10-17mm which I used a lot on my K3. I expect distortion on this lens but have been surprised how well LR6 takes care of it, even at 10mm. I don't know what I expected but for the money, the distortion is more than I bargained for. LR6 is not doing much in correction. Anyway, thanks for your comments; I will let you know how I go in Yosemite. Rgds, John

09-03-2017, 08:38 AM	#9
Bad Boy Junior Member Join Date: Jan 2013 Location: Western Washington State Posts: 41	I find this distortion can add to the creativity of a photo. Some times it does not. Then there are tilt / shift software programs that can correct this distortion. As you can see wide angle lenses make vertical elements in architectural photography lean. More so if the camera is aimed up or down. I have used a free program call ShiftN to straighten the vertical elements. Some of the picture will be cropped when using this so compose your images a bit wide.

09-03-2017, 09:21 AM	#10
aurele Veteran Member Join Date: Jan 2011 Location: Paris, France Photos: Albums Posts: 3,217	It's more the "wide angle" PoV rather than the distortion that's obvious. The distortion is rather low IMO.

09-03-2017, 11:09 AM	#11
lytrytyr Pentaxian Join Date: Nov 2011 Photos: Gallery \| Albums Posts: 4,310	Originally posted by frankoz I am finding significant distortion (see attached link) which even Lightroom 6 with the appropriate lens adjustment doesn't fix. Can you do a custom correction of the geometric distortion instead? I've had problems with the automatic vignetting correction of my DA 20-40 at the long end, and have found that I can do better manually with the custom correction (in Photoshop). As it happens, I was just watching Nolan's "Interstellar", and I couldn't help noticing the geometric distortion on the wide-angle shots of the interior of the farmhouse. So if you can't get the corrections done, just pretend that it's for artistic effect!

09-03-2017, 03:28 PM	#13
Sandy Hancock Moderator Site Supporter Join Date: Feb 2012 Location: Adelaide Hills, South Australia Photos: Gallery \| Albums Posts: 11,272	Comparing a fisheye to a rectilinear UWA is not really fair - it is precisely the lack of barrel distortion of the latter that produces the wild corners. Use it creatively as others have pointed out.

09-03-2017, 04:44 PM	#14
rawr Veteran Member Join Date: Jun 2009 Posts: 11,913	Judging from the reviews of the Tamron 15-30, distortion at 15mm is there, but tolerable. On par with other ultra-wide zooms. (from the lenstip review of Tamron 15-30) It will have some impact on corner sharpness though, particularly wide open.

09-03-2017, 06:00 PM	#15
clackers Otis Memorial Pentaxian Join Date: Jul 2013 Location: Melbourne Photos: Albums Posts: 16,397	You must not have much experience of ultra wides on full frame, Frank? Looking at DXO, the mighty Nikon 14-24mm f2.8 has similar distortion. Less at 15mm, but more vignetting as a tradeoff. The dedicated Samyang 14mm prime has similar distortion. So, it's par for the course, your technique and framing will need to be up to shooting UWA. Use the horizontal/vertical level lines in the viewfinder!