Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
01-27-2008, 06:00 PM   #16
Site Supporter




Join Date: Sep 2006
Location: midwest, United States
Photos: Gallery
Posts: 3,242
The moon is not necessarily at infinity for long lenses like a telescope. Focus them on the moon and the stars (which are farther away) can be out of focus. Look forward to trying the K20D with live view on the telescopes. Have scopes far bigger than the C8 Celestron (nice scope) to try.
thanks
barondla

01-27-2008, 06:20 PM   #17
Veteran Member
jeffkrol's Avatar

Join Date: Sep 2006
Location: Wisconsin USA
Photos: Gallery
Posts: 8,434
QuoteOriginally posted by barondla Quote
The moon is not necessarily at infinity for long lenses like a telescope. Focus them on the moon and the stars (which are farther away) can be out of focus. Look forward to trying the K20D with live view on the telescopes. Have scopes far bigger than the C8 Celestron (nice scope) to try.
thanks
barondla
Will being restricted to Iso1600 in bulb mode be a problem for astrophotos????
01-27-2008, 06:25 PM   #18
Pentaxian
falconeye's Avatar

Join Date: Jan 2008
Location: Munich, Alps, Germany
Photos: Gallery
Posts: 6,863
Original Poster
QuoteOriginally posted by barondla Quote
The moon is not necessarily at infinity for long lenses like a telescope. Focus them on the moon and the stars can be out of focus.
Sure?
Moon is 400000 km. Even with at 1000x, this is like 400 km at 1x. Should still be infinity.

However, the moon is harder to focus amd may give the impression of a separate focus.

Or am I wrong here?
01-27-2008, 06:36 PM   #19
Veteran Member
Duck Dodgers's Avatar

Join Date: Dec 2007
Location: in the 24½th Century!
Photos: Gallery
Posts: 439
QuoteOriginally posted by falconeye Quote
Sure?
Moon is 400000 km. Even with at 1000x, this is like 400 km at 1x. Should still be infinity.

However, the moon is harder to focus amd may give the impression of a separate focus.

Or am I wrong here?
Most telescopes focus past infinity. They mostly use a rack and pinion system, and a wide variety of eyepieces, and "infinity" is different for each one.


Here's one with eight inches of travel.

01-28-2008, 12:04 AM   #20
Inactive Account




Join Date: Nov 2007
Location: Grosse Pointe Farms, Michigan
Posts: 190
QuoteOriginally posted by jsherman999 Quote
Yes!!! We'll have to se if the 8x or 10x magnification gives you enough resolution to nail manual focus, better than your eyes + viewfinder that is, but if it can, this is huge, IMO.



.

Yes it does and very well at that. The 8x factor nails it spot on.

Not to shabby for a $3,000 dollar body savings eh?
01-28-2008, 04:47 AM   #21
Veteran Member




Join Date: Nov 2006
Location: Hong Kong
Posts: 1,934
The Negative Side

The negative side is the AF in LiveView is problematic and difficult to use, it does offer AF though:-

Pentax K20D DSLR Digital SLR Review
01-28-2008, 08:32 AM   #22
Veteran Member




Join Date: May 2007
Location: Prince George, BC Canada
Photos: Gallery | Albums
Posts: 644
QuoteOriginally posted by RMabo Quote
For macro or landscape shots, with the 'cam on a tripod, LiveView could be quite handy.
Especially for macro where the short focus distance gives such a tiny depth-of-field.
Also, I am wondering if the mirror is up, would this not be like the MLU feature of old. That is, as opposed to the 2 second delay we now have?

Mike.
01-28-2008, 08:59 AM   #23
Busiko
Guest




QuoteOriginally posted by falconeye Quote
Sure?
Moon is 400000 km. Even with at 1000x, this is like 400 km at 1x. Should still be infinity.

However, the moon is harder to focus amd may give the impression of a separate focus.

Or am I wrong here?
I don't know about telescopes but with long telephoto lenses the focusing movement doesn't stop at the Infinity mark, it's made so to allow for mechanical tolerances with heat and cold. You can't just leave focus at the end stop. It might be away of precise focus, so people need an enlargement device to get it easier.
Rui

01-28-2008, 09:53 AM   #24
Senior Member




Join Date: Sep 2006
Location: Norway
Posts: 267
QuoteOriginally posted by MikePerham Quote
Also, I am wondering if the mirror is up, would this not be like the MLU feature of old. That is, as opposed to the 2 second delay we now have?

Mike.
I just had a chat woth the norwegian distribuor about this topic. According to them the answer to your question is yes.
Hopefully this will eliminate some vibrations and enable us to use longer shutter speeds. Cool
01-28-2008, 10:18 AM   #25
Inactive Account




Join Date: Jul 2007
Location: Helsinki, Finland
Posts: 21
Closing aperture in live view?

How aperture size is working in Live View?

I mean, you probably want to focus with open aperture (and most probably live view function works initially at biggest aperture available), but can you close the aperture down to check depth of field, and is the view struggling to gain enough light at that moment?

With macro shooting this is crucial, as the live view itself will be when the pics are taken at positions where looking through the viewfinder is blocked or very difficult.

-Veijo-
01-28-2008, 10:28 AM   #26
Veteran Member
Tom M's Avatar

Join Date: Aug 2007
Location: Lincoln Park, NJ
Photos: Gallery
Posts: 782
QuoteOriginally posted by jeffkrol Quote
Will being restricted to Iso1600 in bulb mode be a problem for astrophotos????
What? Tell me that isn't true!

With the K10D I can set it to whatever I like!
01-28-2008, 10:59 AM   #27
dbh
Inactive Account




Join Date: Jan 2007
Location: Edmonton
Photos: Gallery
Posts: 404
I use a T-mount adapter on a Meade 2120 and put the camera at the prime focus (as opposed to using eyepiece projection). If the moon is up, it is often so bright I can focus easily on a lunar crater and then don't touch the focusing screw after that.

What I have been anxious to try is using the 1.7X AF adapter with the telescope and see if it does a better job of focusing than I do. Might help avoid my periodic total loss of dark adapted vision too if I don't have to look through the viewfinder at the moon. The wired remote I made has a separate button for AF and a toggle switch for shutter release.
--
dbh
01-28-2008, 12:13 PM   #28
New Member




Join Date: Jan 2008
Posts: 13
Another odd but potentially useful use for liveview (assuming you can turn off any sleep function) is using the video out of the K20D and inputting it into the Video input of a video camera such as an HD cam or miniDV Cam for recording what the K20 sees. I know you won’t get 14mp but what made me think of such a setup was my desire to set the video camera low on a tripod and film a sunrise or sunset at an extreme angle such as a fisheye then speed up the shot so you can watch the sun/moon race up the sky. However, the DV cam I have isn’t wide enough and I have no desire to purchase any fisheye/wide angle adapters for it, but I do have fisheye photo lenses and tele lenses that won’t work with the DV cam….. Just a thought…..
01-29-2008, 01:01 PM   #29
Veteran Member




Join Date: Dec 2006
Location: LI, NY
Posts: 313
QuoteOriginally posted by jsherman999 Quote
Yes!!! We'll have to se if the 8x or 10x magnification gives you enough resolution to nail manual focus, better than your eyes + viewfinder that is, but if it can, this is huge, IMO.
.
According to one reviewer, the magnifications are supposedly pixellated, so difficult to use. If this is the only special "feature" of Pentax Live-View, then they should get at least that right. If that tester was correct, hopefully it clears up in production release firmware.

If Pentax wants to include a feature that other cameras made popular, they should at least implement it in the best current way.

That is with "Contrast Detect" focusing, so you can focus while using live-view,

and "Exposure Simulation", so you can verify exposure as well. Both on Canon cameras.

Pentax could have done research, and seen this implemention on Canon's 40D well before the K20D was finished, and now even on the entry level 450D.
01-29-2008, 02:45 PM   #30
Veteran Member




Join Date: Dec 2006
Location: Copenhagen
Photos: Gallery
Posts: 1,845
QuoteOriginally posted by Pål Jensen Quote
It is but finding exact infinity in a lens is very difficult.

1. Wide open, fast lens = miniscule DOF.
2. Temperature variations change the position of infinity on the lens. A, say 25 degree Celcius variation in temperature makes a difference.
3. Many lenses focus past infinity. All super telephotos and the eg the FA Limiteds. This to compensate for thermal contraction/expansion.
4. Precision in the mirror finder system is never 100% and will vary from camera to camera.
5. True focus or ever so slightly off is hard to see on a focusing screen.
6. Precise focusing in low light, infinity or not, is virtually impossible.

The only way to ensure absolutely focus is on the film/sensor plane.
High magnification live view will be a very useful to astro and aurora photographers.
Some examples:

Here I stopped down the 77 Limited to F:3.5 in order to be certain infinity was in focus:
Red Aurora. Raftsundet, ...: Photo by Photographer Pål Jensen - photo.net

Here I stopped down either the A 24/2.8 or the 31/1.8, can't remember wich lens I used, to F:4 for the same reason.
Aurora Borealis in moonlight. ...: Photo by Photographer Pål Jensen - photo.net

Hi Pål,
Thanks a lot for this very precise, but still readable post.
Outstanding pictures also to illustrate.

BTW, you got some very fine feedback in this thread :
Re: For Roland +1: Pentax SLR Talk Forum: Digital Photography Review
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!
10x, af, focus, k20d, lens, lenses, liveview, pentax news, pentax rumors, series
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
K20D leaves a line on the right side of photo. ? Craig66 Pentax DSLR Discussion 16 12-02-2010 07:00 AM
K20D, LiveView and manual focusing skb0 Pentax DSLR Discussion 9 07-19-2010 05:40 PM
Travel Cambodja, now the positive side bymy141 Post Your Photos! 17 04-21-2010 01:58 AM
K20D Liveview problem Malsi Pentax DSLR Discussion 3 02-16-2010 04:36 PM
K20D & DA 50-200 out side my office Ed in GA Post Your Photos! 9 04-12-2008 03:39 AM



All times are GMT -7. The time now is 04:58 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