Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
10-09-2016, 03:33 PM   #1
Senior Member
mhoule418's Avatar

Join Date: Jan 2013
Location: Quebec city
Posts: 228
Which focal lenght to enter?

Good evening all,

I recently aquired a SMC-Pentax-A-35-105mm-F3.5. When I mount it on my K-5ii (or other bodies), I am asked to provide the FL of the lens. I know this is related to Shake Reduction.

I always wonder which FL to enter. Should I enter the 35mm (min) or the 105mm (max) value or something in between?

I guess that if I plan to use it at the max spectrum most of the time, I should enter 105mm.
But since it's a zoom, you never know in advance what will be the target opportunity.

Is there any rules of thumb to follow?
How would you do it?

Thanks in advance.

10-09-2016, 03:43 PM - 1 Like   #2
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 51,584
See this thread and the accompanying links:
https://www.pentaxforums.com/forums/151-pentax-k-30-k-50/253121-manual-focus-...h-setting.html

There are a number of viable approaches that you can take.

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)



PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:
10-09-2016, 05:06 PM   #3
Senior Member
mhoule418's Avatar

Join Date: Jan 2013
Location: Quebec city
Posts: 228
Original Poster
Thanks Adam,

I was sure this topic was already talked about.
10-09-2016, 10:18 PM   #4
Site Supporter




Join Date: Sep 2006
Location: New England
Photos: Gallery | Albums
Posts: 1,286
QuoteOriginally posted by mhoule418 Quote
I recently aquired a SMC-Pentax-A-35-105mm-F3.5. When I mount it on my K-5ii (or other bodies), I am asked to provide the FL of the lens. I know this is related to Shake Reduction.

I always wonder which FL to enter. Should I enter the 35mm (min) or the 105mm (max) value or something in between?

I guess that if I plan to use it at the max spectrum most of the time, I should enter 105mm.
But since it's a zoom, you never know in advance what will be the target opportunity.

Is there any rules of thumb to follow?

I think, from the thoughtful way you have considered the problem and have framed your question, that, even ~without~ any further advice, you will end up with a workable solution just by yourself.

I will just add my own strategy, FWIW: I also use and like the A 35-105/3.5 (on a K-3), and what I now try to do, using that lens for the example -

1. As a generality, unless I know ahead of time that I am very highly likely to be using it primarily at one end of the FL range or the other, I set it (at bootup or from the menu) about 1/2-way in between.

2. I navigate thru the menu to the "Input Focal Length" (Record menu 3, I think) setting (even if I've already set the FL when the cam booted) to make sure that the Menu will open again to that setting right away (in case I need to change it in a hurry).

[Note 1 -- For #1, obviously if I know I am, say, going to be shooting portraits, then I might set the FL for greater than 1/2-way from 35 to 105, or if I know I am, say, going to be shooting scenics, then I might set it for less than 1/2-way from 35 to 105, etc...]

[Note 2 -- For #2, obviously I have to also have the setting for "Save Menu Location" (Custom menu 4, I think) turned on for it to work.]

10-10-2016, 03:27 AM   #5
Veteran Member




Join Date: Jul 2009
Location: Tromsų, Norway
Photos: Albums
Posts: 1,031
Choose the FL you intend to use. If you zoom away from that, change the FL in the menu accordingly. Or just turn off SR and forget about setting it.
10-10-2016, 03:43 AM   #6
Site Supporter
Site Supporter




Join Date: May 2015
Location: Hampshire
Photos: Gallery | Albums
Posts: 892
If you are going to use it at speeds faster than 1/250th second, turn off the SR.
I found that using a legacy macro lens at full extension I needed a longer FL input to have a more effective SR bonus.
I have some doubts about what FL to choose with legacy lenses anyway due to the actual length differences over lenses that have the same FL. Also I imagine the amount of shake generated by different people will not necessarily covered by the SR in the camera, different people, different amount of shake.
If you are shooting speeds slower than the focal length then SR set to the FL being used the most.....or set to between the minimum FL and maximum FL depending where you find the most benefit after some testing. A quick test of your lens (which is one of my favourites) might help to that finding.


Whatever you choose to do, try and learn your best technique for holding the camera and lens as steady as possible and pressing the shutter release as smoothly as possible when shooting.
My opinion only, not necessarily correct.
10-12-2016, 12:11 AM - 1 Like   #7
Veteran Member




Join Date: Jan 2010
Location: Southern England
Posts: 623
I have to do this from time to time (don't know why):

"If you want a compromise focal length, use the following:

2*min*max/(min+max)

This will equalise the amount of shake reduction at both ends of the zoom range. So, for a 35-105, set 50mm for the closest approximation.

Best SR results are obviously when you set the focal length to the value which you input to the camera. But don't make the mistake of inputting, say, 105mm and then forgetting and operating at the 35mm end. Because you'll end up magnifying the shake-induced blur. The other way round is fine though (i.e. telling the camera it's a 35 and operating at 105mm) - it's just that you won't get optimum shake reduction."

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!
105mm, 35-105mm, advance, fl, k-mount, manual lens, max, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Setting proper focal lenght with K-1 and manual lenses Sylwester Pentax K-1 & K-1 II 5 06-23-2016 03:46 AM
K-1 not asking for focal lenght... Gutta Perka Pentax K-1 & K-1 II 9 05-29-2016 08:08 AM
Focal lenght comparison with Teleconverter Scootatheschool1990 Pentax SLR Lens Discussion 7 05-10-2013 12:56 PM
manual lens macro focal lenght question Frank Bowler Troubleshooting and Beginner Help 5 12-10-2010 10:23 PM
K100D: What focal length to enter? newarts Pentax SLR Lens Discussion 8 12-28-2008 11:33 PM



All times are GMT -7. The time now is 03:17 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