Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
10-23-2017, 01:33 PM   #1
New Member




Join Date: Nov 2016
Posts: 13
Custom input focal lenght for astrotracer

Hi folks, I'm using thirdparty and legacy 6x7 glass with an adaptor on my K1 for astrophotography, the results are outstanding but I've encountered a problem when using a 14mm lens and when using a 1.4x converter. So a 200mm lens becomes a 280mm lens with the converter. The problem is there is no 280mm input focal lenght in the drop down menu. The result is that the astrotracer feature does not have the correct focal lenght info and therefore fails to keep stars from trailing. Is there a way to input custom focal lengths like 14mm, 105mm, 280mm, 420mm or 560mm ?

10-23-2017, 01:40 PM   #2
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 49,673
Unfortunately there isn't. For the astrotracer you'll perhaps want to enter the nearest focal length below 280mm, so that it doesn't over-compensate.

Also, longer lenses significantly limit the number of seconds you can effectively use the astotracer, so don't expect it to go for as long as you do with that 14mm

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, 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:

10-23-2017, 02:43 PM   #3
New Member




Join Date: Nov 2016
Posts: 13
Original Poster
QuoteOriginally posted by Adam Quote
Unfortunately there isn't. For the astrotracer you'll perhaps want to enter the nearest focal length below 280mm, so that it doesn't over-compensate.

Also, longer lenses significantly limit the number of seconds you can effectively use the astotracer, so don't expect it to go for as long as you do with that 14mm
Thanks Adam, the focal length is critical for longer lenses, there is no tolerence even with 5mm as seen with my 105mm set to 100 and yes the astrotracer has it's limitations. Maybe Pentax could include a work around in a firmware update but I suppose the use of 6x7 glass is "a niche market" so probably not :-( Still the astrotracer is fantastic when used with proper input focal lenght though, even with the longer lenses and shorter exposures, thanks for the reply.
10-23-2017, 07:58 PM - 1 Like   #4
Forum Member




Join Date: May 2016
Photos: Gallery
Posts: 96
Agree would be a nice touch to have the option of entering the correct focal length. I have a few lenses I cannot enter Zeiss 25, Voigtlander 58 and 90. I think it would also help with some third party software because they incorrectly add lens profiles based on the focal length.

10-24-2017, 01:31 AM - 1 Like   #5
New Member
Kickmansch's Avatar

Join Date: Feb 2013
Posts: 10
I've never quite understood why 14mm is not an option to enter as a focal lenght on the K1, Pentax did have the 14mm 2.8 Fisheye right ? Or is the list of possibilities only populated with legacy pentax focal lenghts that didn't have a chip to electronically give the FL to the camera body ?

For the same reason the lovely Tokina 17mm 3.5 won't go with Astrotracer as well, allthough that one isn't really fast enough for Astro anyway it's useless at f3.5, yet pretty neat at f11.
10-24-2017, 03:00 PM - 1 Like   #6
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 49,673
I agree, it would be nice if they could have two modes- quick selection with the most common focal lengths, and advanced, which lets you just type it in.

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, 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:

03-31-2018, 11:09 AM   #7
New Member




Join Date: Mar 2018
Posts: 12
I have a similar (but worse) issue - I can't set the FL at all when I attach a fully manual 'lens' using a t-adaptor. The 'set focal length' menu option is greyed out. And astrotracer doesn't work at all, so i'm guessing that this is because the focal length is 0.0.

It's not clear why astrotracer needs the FL at all, except for the estimate of max exposure time.

Astrotracer does work with my manual focus Rokinon 135 mm lens. The cam (K-70) asks for the FL when turned on.

David
04-01-2018, 08:24 AM   #8
Site Supporter
Site Supporter




Join Date: Nov 2015
Photos: Albums
Posts: 2,129
Is this possibily one of those ‘shorting out the contacts’ things?

I don’t have any problems with a couple of t-mount lenses I have letting me enter the focal length on my K1. Maybe it’s characteristic of your particular adapter? I’m using a cheap eBay thing...

But I thought focal length was essential to allow the camera to know how far to move the sensor over a given time...

-Eric

04-02-2018, 01:59 PM   #9
New Member




Join Date: Mar 2018
Posts: 12
QuoteOriginally posted by TwoUptons Quote
Is this possibily one of those ‘shorting out the contacts’ things?

I don’t have any problems with a couple of t-mount lenses I have letting me enter the focal length on my K1. Maybe it’s characteristic of your particular adapter? I’m using a cheap eBay thing...

But I thought focal length was essential to allow the camera to know how far to move the sensor over a given time...

-Eric
Sorry - yes, of course the FL is necessary, in order to know how fast to move the sensor.

I tried shorting out the contacts with aluminum foil, but no matter how I tried covering the contacts, the cam never asked for FL, and the menu setting for selecting FL never enabled.

Others have said that the K-1 does not have this problem, but all I know for sure is that with my K-70, even with the latest firmware installed, I cannot set the FL for the OTA connected by a t-adapter.

David
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, astrotracer, converter, custom, custom input, dslr, full frame, full-frame, input, input focal lenght, k-1, k1, lenght, lens, pentax k-1
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Which focal lenght to enter? mhoule418 Pentax SLR Lens Discussion 6 10-12-2016 12:11 AM
Setting proper focal lenght with K-1 and manual lenses Sylwester Pentax K-1 5 06-23-2016 03:46 AM
K-1 not asking for focal lenght... Gutta Perka Pentax K-1 9 05-29-2016 08:08 AM
Focal lenght request with DA 20-40 RobertCh Troubleshooting and Beginner Help 7 07-23-2014 10:58 AM
K5 Custom input focal length Nokton Pentax K-5 9 03-14-2011 06:22 AM



All times are GMT -7. The time now is 09:36 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