Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
03-24-2016, 12:27 AM   #1
Junior Member




Join Date: Apr 2015
Posts: 32
KA mount lens on a K5II

Hello everybody! I just received my Lester A.Dine 105mm Macro lens and started to play with this beauty. One thing puzzles me - when I switch on the camera with the lens attached, I'm asked to dial in the focal length of the lens. Should I dial 100mm (full frame focal length) or 150mm (cropped sensor equivalent)? Tried both and don't see any difference in images so far.

03-24-2016, 12:34 AM   #2
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 27,415
Enter the actual focal length of the lens or the closest of available choices.


Steve
03-24-2016, 12:49 AM   #3
pjv
Moderator
Loyal Site Supporter
pjv's Avatar

Join Date: Mar 2015
Location: Melbourne, Australia
Photos: Gallery
Posts: 4,644
QuoteOriginally posted by Buruny Quote
One thing puzzles me - when I switch on the camera with the lens attached, I'm asked to dial in the focal length of the lens

Hi Buruny. Because your camera doesn't recognize your lens, you must tell it the focal length so the camera will know how much " Shake Reduction " to use. If you dial in 100, that will be close enough. Good luck.
03-24-2016, 10:29 AM   #4
Senior Member




Join Date: Dec 2013
Location: Buffalo, NY
Posts: 289
Unless you've used 35mm film for years or plan to switch to the full frame K-1, you can completely forget about 'equivalence'.

A lenses focal length and aperture do not change, regardless of the sensor, so you should dial in the actual focal length marked on the lens. The resulting image would be different since the crop sensor covers a smaller area, but the whole idea of equivalence was so people who were used to thinking in terms of 35mm full frame could quickly get an idea of how something would perform on a crop sensor, mostly in relation to field of view and depth of field. If you have no frame of reference, worrying about the equivalence calculation is just wasted thought process.

Think of it like inches and centimeters. If you grew up thinking in inches, you might convert lengths from centimeters to inches to help you picture them in your head. If you've grown up thinking in centimeters there's no reason to consider the equivalent in inches, so you just stick with centimeters. The only time 'equivalence' comes in is when you have to move between the two systems and want to understand the relation, the same with full frame and crop sensors.

Honestly, equivalence is most useful for knowing what focal length on a crop camera gives approximately the same field of view as a certain focal length on a full frame or vice versa. There are more technical details and comparisons beyond that, but if you're just starting out and only use APS-C then that's more than you need to know.

03-25-2016, 10:56 AM   #5
Junior Member




Join Date: Apr 2015
Posts: 32
Original Poster
Thank you! All is clear now.
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!
camera, dslr, ka mount lens, length, lens, photography
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: TAMRON 400MM Adapatall 2 lens with KA mount spartan Sold Items 23 04-30-2016 05:21 PM
KA mount lenses won't fully attach on a K-X cbhicks Pentax SLR Lens Discussion 6 03-17-2012 07:51 PM
For Sale - Sold: CPC 70-210mm f/4 KA-mount auto-aperture lens, Pentax SMC-A copy, Worldwide shi wallyb Sold Items 15 10-21-2009 03:16 PM
For Sale - Sold: Pentax SMC-A 50mm f/1.7 KA-mount Prime lens, Worldwide Ship! wallyb Sold Items 4 09-24-2009 09:09 PM
What kind of Vivatar lens is a P/KA mount? Eastern Shore Charlie Pentax SLR Lens Discussion 4 04-17-2007 10:27 PM



All times are GMT -7. The time now is 06:18 PM. | 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