Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
12-14-2009, 07:24 AM   #1
Site Supporter




Join Date: Oct 2007
Location: Madrid, Spain
Posts: 117
Cropping a DA 15mm Tests

Has any owner of a 15DA tested cropping to 24mm focal length on a 10KD? I am very interested in this lens but would like to be able maximize its use by cropping without losing too much IQ. Thanks,
Earl

12-14-2009, 10:31 AM   #2
Pentaxian
reeftool's Avatar

Join Date: Dec 2007
Location: Upstate New York
Photos: Gallery | Albums
Posts: 8,139
Why not just buy a 24mm or the 12-24 zoom?
12-14-2009, 11:51 AM   #3
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
Well, a 24mm can't be cropped to provide the FOV of a 15mm, meaning you'd need two lenses to cover the same range, and the 12-24 is quite a bit larger than the 15 - plus it has a whole heck of a lot more distortion and CA.

I haven't done any formal tests of my DA15, and have no other primes wider than 28mm to comapre with even if I wanted to. But my sense is that on a 10MP camera like the K10D (or in my case, the K200D), cropping the DA15 to the equivalent of 21mm is not a problem at all. You cut out the borders which are the softest part of the DA15's image (only an issue at apertures of f/5.6 and larger), and are still left with enough resolution to be useful. 24mm might be pushing it for larger prints but should be fine for web and small prints.

If I'm doing the math correctly, to crop an image from a 15mm to a 21mm FOV means a "crop factor" of 1.4, and going from 15mm to 24mm means a "crop factor" of 1.6. Since the crop is applied both horizontally and vertically, that means you lose pixels at a rate of the crop factor squared. So if you start with a 10MP camera, a crop to 21mm FOV leaves you with 5MP, and a crop to to 24mm FOV leave you with 4MP.

Of course, this is ll for naught if the lens isn't sharp enough to withstand this sort of cropping, but the DA15 measured resolution numbers are astronomical for the center, which is what we're using. Again, I have no way to really do much of a comparison except I suppose to the kit lens, but my subject impression without doing a controlled test is that results would be exactly as good as you'd hope a 4MP image could be.
Subjectively
12-14-2009, 12:57 PM   #4
Site Supporter




Join Date: Oct 2007
Location: Madrid, Spain
Posts: 117
Original Poster
Thank you Marc. I forgot about looking at the DA 15's resolution numbers. 4MP is good enough for my printing. I really like the idea of walking around with a small 15mm.
Again, thank you,
Earl

12-14-2009, 01:42 PM   #5
Veteran Member




Join Date: Feb 2007
Location: Ontario
Photos: Gallery
Posts: 630
QuoteOriginally posted by merengue Quote
Thank you Marc. I forgot about looking at the DA 15's resolution numbers. 4MP is good enough for my printing. I really like the idea of walking around with a small 15mm.
Again, thank you,
Earl
I love going walk-about with my 17/4 fisheye which is also very small, the 15mm I'm sure would be a joy to use in that same capacity. I'd say give it a try!
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!
da 15mm, k-mount, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Landscape Its Cropping Time rustynail925 Post Your Photos! 0 03-11-2010 11:34 PM
A question of cropping FHPhotographer Digital Processing, Software, and Printing 5 10-26-2009 08:08 PM
Cropping too much out of a picture??? MoparFreak69 Post Your Photos! 11 08-20-2009 06:32 AM
What should be the maximum price for Pentax-A 15mm lens as the DA 15mm is coming up? Mitch34 Pentax SLR Lens Discussion 6 06-24-2008 04:40 PM
Cropping by mm regken Pentax DSLR Discussion 3 01-11-2007 11:10 PM



All times are GMT -7. The time now is 03:34 AM. | See also: NikonForums.com, CanonForums.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