Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
11-16-2015, 05:56 AM   #1
Forum Member
Alnjpn's Avatar

Join Date: May 2015
Location: Osaka
Posts: 84
Should the Samyang 14mm 2.8 be this soft?

I recently purchased a Samyang 14mm 2.8 for night photography. Particularly city scapes and night sky photography. I took it out for the first time tonight for a try and it does seem very soft at 2.8. Is this softness of another issue?. These are some center crops from photos taken on a K30. They are f2.8, f4, f5.6 and f8. Things look better at f4 and very good at F5.6 and F8. But at 2.8 it is unusable.

Attached Images
View Picture EXIF
PENTAX K-30  Photo 
View Picture EXIF
PENTAX K-30  Photo 
View Picture EXIF
PENTAX K-30  Photo 
View Picture EXIF
PENTAX K-30  Photo 
11-16-2015, 06:02 AM   #2
Veteran Member
PePe's Avatar

Join Date: Nov 2007
Location: Helsinki, Finland
Photos: Gallery | Albums
Posts: 452
At f:2,8 the lens is definitely soft. How much did you crop the picture?
11-16-2015, 06:33 AM   #3
Pentaxian
Outis's Avatar

Join Date: Apr 2014
Location: Cambridge, MA
Posts: 899
Also, are these crops from the side of the image? It's common for Rokinon lenses to have problems with decentering.
11-16-2015, 07:25 AM   #4
Pentaxian
Na Horuk's Avatar

Join Date: Feb 2012
Location: Slovenia, probably
Photos: Gallery | Albums
Posts: 10,331
Is that the whole image? Because the centre should not look like that. Are you sure the front and back elements are clean?
That said, its possible that you misfocused, because Samyang 14mm often comes with uncalibated focusing ring. So infinity is really not where the little infinity mark is labelled. It is possible to focus past infinity. At f2.8 the DoF is still relatively shallow, despite the lens being 14mm.

I never took a night landscape photo like that wide open with my Samyang 14mm, but I think that first photo looks a bit odd.

11-16-2015, 08:15 AM   #5
Pentaxian
VisualDarkness's Avatar

Join Date: Nov 2011
Location: Uppsala, Sweden
Photos: Gallery
Posts: 4,439
The pics looks misfocused.
11-16-2015, 08:16 AM   #6
Forum Member
Alnjpn's Avatar

Join Date: May 2015
Location: Osaka
Posts: 84
Original Poster
These are crops close to the center. The original is like this. As you mentioned it could be focus issues, I hadn't realized that the depth of field was still shallow at infinity on this lens. I think I probably have to play around and find its real infinity at 2.8. Is there an easy way to do this? Thanks, I appreciate the help.
11-16-2015, 08:24 AM   #7
New Member




Join Date: Mar 2015
Posts: 21
I have this lens too, nice piece of glass, but indeed do not trust the focusring. I take nightpictures at F8 or higher. Greets.
11-16-2015, 08:35 AM   #8
Senior Member




Join Date: Jul 2012
Photos: Gallery
Posts: 173
QuoteOriginally posted by Alnjpn Quote
These are crops close to the center. The original is like this. As you mentioned it could be focus issues, I hadn't realized that the depth of field was still shallow at infinity on this lens. I think I probably have to play around and find its real infinity at 2.8. Is there an easy way to do this? Thanks, I appreciate the help.
As with any manually focused lens, using the live screen and magnifying the view is the best way to see if the lens focuses beyond infinity. The other way is to simply start at infinity where the lens is going to be the softest (if this case f/2.8) and then start turning the focusing ring just a little with each photo for about 3/8" (five or six photos total). If the lens is sharper at a point other than infinity, keep doing this until the perfect spot is found and mark it. Now you know where to focus for those astro shots.

How soft is the lens at f/2.8 and how much contrast is lost? Photozone does a great job testing these lenses. They didn't test this lens with a Pentax body, but you can still find out how it performed on the photozone.de site.

Oh yeah, was there any shaking of your tripod? Was the camera just set on a ledge and you simply pushed the shutter button? Perhaps a little further testing is in order before deeming the lens a "bad copy," which it could be.


Last edited by quant2325; 11-16-2015 at 08:41 AM.
11-16-2015, 08:37 AM   #9
Loyal Site Supporter
AquaDome's Avatar

Join Date: Jan 2014
Location: New Carlisle, IN
Photos: Gallery | Albums
Posts: 1,403
QuoteOriginally posted by Alnjpn Quote
I think I probably have to play around and find its real infinity at 2.8. Is there an easy way to do this? Thanks, I appreciate the help.
With the camera on a tripod and shake-reduction off, focus on something at infinity (200X the focal length). You can use focus-peaking for this. When focus is sharp at infinity, make a mark on the focusing scale so you can find infinity again. Some lenses allow you to adjust the scale by loosening a screw.
11-16-2015, 08:42 AM   #10
Forum Member
Alnjpn's Avatar

Join Date: May 2015
Location: Osaka
Posts: 84
Original Poster
Thanks again, I really appreciate the help. I am going to see what I can do and report back.
11-16-2015, 09:24 AM   #11
Pentaxian




Join Date: Jan 2011
Location: New York
Posts: 3,016
As others have said, it could be misfocused. I'll add that flare or other optical aberrations with bright lights might contribute to the blurred look at f2.8. My version of the 14/2.8 is good for astrophotography but it does less well for city nightscapes.

Do some tests during the day as well as at night.
11-16-2015, 11:11 AM   #12
Senior Member
Nitrogliserin's Avatar

Join Date: Apr 2013
Location: Turkey
Photos: Gallery
Posts: 191
f2.8 looks out of focus / possible miscalibrated infinity mark or shake issue.

Also even the smallest touch or wind could effect the results. Try to shoot either with timer or put the camera on a much stable place rather than tripod. For tripod you can also close the last legs.
11-17-2015, 05:01 AM   #13
Forum Member
Alnjpn's Avatar

Join Date: May 2015
Location: Osaka
Posts: 84
Original Poster
After some controlled testing I have found that this lens reaches its best at the dead stop. It looks as though the image still has room to improve beyond the stop. I found a thread on dpreview where the poster had a similar issue, he adjusted his lens to give him an extra 3mm past the stop which improved the image. Since I am not up to that kind of adjustment I am planning to exchange it for another copy.
11-17-2015, 08:05 AM   #14
Pentaxian
Na Horuk's Avatar

Join Date: Feb 2012
Location: Slovenia, probably
Photos: Gallery | Albums
Posts: 10,331
QuoteOriginally posted by Alnjpn Quote
Since I am not up to that kind of adjustment I am planning to exchange it for another copy.
There is a youtube video of this adjustment, it is very simple, takes 5 minutes. At least watch the video before you decide.
I doubt you will ever get a Samyang 14mm lens that is properly calibrated; but you might find one that is miscalibrated in such a way that is more comfortable for your needs
11-18-2015, 12:28 AM   #15
Senior Member
Nitrogliserin's Avatar

Join Date: Apr 2013
Location: Turkey
Photos: Gallery
Posts: 191
It's super easy! The tutorial video where you can easily adjust the ring.

Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
14mm, camera, f4, f5.6, f8, night, pentax help, photography, samyang, samyang 14mm, troubleshooting
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Samyang/Rokinon 14mm f/2.8 Auto Exposure? lukelbd Pentax SLR Lens Discussion 21 11-17-2016 07:10 PM
Which 14mm f/2.8 is better: Pentax or Samyang (+rebadges)? Auzzie-Phoenix Pentax SLR Lens Discussion 14 07-11-2015 07:33 AM
Experience with Pentax 15mm LTD vs Samyang 14mm 2.8? chickentender Pentax SLR Lens Discussion 30 02-20-2014 11:06 AM
Av mode shutter speed Samyang 14mm/2.8 DeadJohn Troubleshooting and Beginner Help 14 12-05-2013 03:36 PM



All times are GMT -7. The time now is 08:26 PM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top