Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
01-09-2011, 04:37 AM   #1
New Member
Wordslinger's Avatar

Join Date: Dec 2010
Location: Ontario
Posts: 20
Prime Lenses on a KX

Hey folks,

I've just purchased a couple of (old) prime lenses. One is a 28mm f2.5 (Tamron w/adaptall) and the other is a 50mm f2 Pentax (Asahi) lens. I've also purchased a couple of zoom lenses (one is a Tamron 80-210 and the other is a Vivitar 100-300). These are all manual focus lenses.

Here's my issue/question:

When using the zoom lenses, I can hold the shutter half way and it will beep to acknowledge the focus. It's quite accurate when using the zoom lenses.

However, when I attach the prime's, that focus 'beep' confirmation is off. I have to fiddle back and forth, back and forth. And the focus indicator never stays lit. Just a blip. And when it does beep, it's actually not quite in focus... I have to focus completely by eye with these primes.

Any idea what's going on here?


edit:
I may have just had an idea which I will test shortly. Being that the depth of field is so shallow when you get down to f2 or so, could it be that the camera's autofocus is having trouble locking on?

01-09-2011, 12:10 PM   #2
Pentaxian
Paleo Pete's Avatar

Join Date: Jun 2010
Location: Texas
Photos: Gallery | Albums
Posts: 2,872
I've seen that for a long time, I usually don't pay much attention to the beep, other than using it to let me know if I'm close. I mainly pay attention to what I see in the viewfinder, that's what matters...

I don't know if the beep is accurate for manual focus lenses or not, with the kind of wildlife shots I try to get even a tiny bit off shows, and I get bad focus no matter what I do quite often, especially with fast moving subjects like birds.

I'd say don't pay a lot of attention to the beep, pay attention to what you see.

Oh and remember the three P's...Practice, Practice, Practice.
01-09-2011, 01:28 PM   #3
New Member
Wordslinger's Avatar

Join Date: Dec 2010
Location: Ontario
Posts: 20
Original Poster
I've been thinking of looking for a magnifying eyepiece for my Kx. I often find it difficult looking through the viewfinder to really get a sense for where the perfect focus is, especially if the subject is at a bit of a distance. With a zoom, I can zoom in, focus, zoom out and recompose. Have you tried any magnifying eye pieces for your viewfinder? I would always focus manually if I could see a bit better.

I miss the viewfinders of old 35mm cameras, the half circle type that are in focus when the image lines up.
01-09-2011, 01:52 PM   #4
MSM
Veteran Member
MSM's Avatar

Join Date: Dec 2007
Location: Alabama
Photos: Gallery
Posts: 994
QuoteOriginally posted by Wordslinger Quote
I've been thinking of looking for a magnifying eyepiece for my Kx. I often find it difficult looking through the viewfinder to really get a sense for where the perfect focus is, especially if the subject is at a bit of a distance. With a zoom, I can zoom in, focus, zoom out and recompose. Have you tried any magnifying eye pieces for your viewfinder? I would always focus manually if I could see a bit better.

I miss the viewfinders of old 35mm cameras, the half circle type that are in focus when the image lines up.
I would look into a split prism. I know that the Kx is not supposed to have a changeable vf, but many here have done that. There are several threads here regarding the various makers and the way to change the vf screen. I used to have one for my k10. I found it to be more helpful than the magnifying eyecup.

01-09-2011, 02:09 PM   #5
New Member
Wordslinger's Avatar

Join Date: Dec 2010
Location: Ontario
Posts: 20
Original Poster
Hey, fantastic! I had no idea you could get replacement focusing screens. I'm already finding a number of options.
01-09-2011, 02:25 PM   #6
Ira
Inactive Account




Join Date: Mar 2009
Location: Coral Springs, FL
Photos: Gallery | Albums
Posts: 5,218
Try this before you buy anything:

Focus with your lenses wide open, then stop down.

Older lenses, even fast ones, don't play nice with AF.

Also, your primes are trickier to lock in focus because the focus rings on them are more precise than the zooms. Tiny movements throw it off focus as far as the confirmation goes, but that doesn't necessarily make the shot out of focus.
01-09-2011, 02:53 PM   #7
Site Supporter
boriscleto's Avatar

Join Date: Dec 2009
Location: Liverpool, NY
Photos: Gallery
Posts: 12,309
QuoteOriginally posted by Ira Quote
Try this before you buy anything:

Focus with your lenses wide open, then stop down.

Older lenses, even fast ones, don't play nice with AF.
He's not using screw-mounts, he's using K-mounts. K-mounts are always wide open until you hit the green button.


AF cameras are notorious for being tricky to focus with MF lenses faster than f/2.8 because of the lack of micro-prism focusing aids in the focusing screen.
01-11-2011, 06:50 AM   #8
Pentaxian




Join Date: Oct 2010
Photos: Gallery | Albums
Posts: 2,663
I think that you will have to learn focusing by eye. I have faced that problem too. But with my K-7. micro adjustment for lense might be good too...it might be off. But I don't know if it is possible in K-X.

I have been thinking of purchasing a splitprism too...but after practising I have managed to get focus at place. Also what i have read from other threads from this forum, about focus praceting is not a bad idea. It does not cost you anything at digital era, just effort

01-11-2011, 08:16 AM   #9
Ira
Inactive Account




Join Date: Mar 2009
Location: Coral Springs, FL
Photos: Gallery | Albums
Posts: 5,218
QuoteOriginally posted by boriscleto Quote
He's not using screw-mounts, he's using K-mounts. K-mounts are always wide open until you hit the green button.


AF cameras are notorious for being tricky to focus with MF lenses faster than f/2.8 because of the lack of micro-prism focusing aids in the focusing screen.
How does the Green button stop down the lens on an Asahi Takumar?
01-11-2011, 08:41 AM   #10
Forum Member




Join Date: Feb 2009
Location: Manila, Philippines
Posts: 97
I'll second the split-screen. I've had one in my K20D for years, and I just received another one (from jinfinance again on ebay) for my Canon 40D.

The K20D required some adjustment of the shim to get MF and AF to agree, but the 40D (as confirmed with my single EF lens, and my manual-focusing with Live View) is accurate, no need to shim.

The split-image screen just takes all the guesswork out of manual focusing (assuming it's bright enough for the split-circle to not go dark). It's just annoying when it doesn't agree with AF!
01-11-2011, 01:43 PM   #11
Site Supporter
boriscleto's Avatar

Join Date: Dec 2009
Location: Liverpool, NY
Photos: Gallery
Posts: 12,309
QuoteOriginally posted by Ira Quote
How does the Green button stop down the lens on an Asahi Takumar?
Where did he say anything about an Asahi Takumar? He mentions a Tamron Adaptall and an Asahi Pentax 50 f/2, both K-mount. That is unless Asahi produced a 50mm f/2 Tak that I've never heard of.
01-11-2011, 02:01 PM   #12
Pentaxian
ryan s's Avatar

Join Date: Jan 2008
Location: Madison, WI
Photos: Gallery
Posts: 2,370
Some say the focus confirm is more accurate when you focus past your intended point, then slowly come backwards. In my experience, it does work a little better.

Still, the best focus confirm tool is your eye

Does the K-x offer interchangeable screens? I was under the understanding it doesn't but I'd love to be proved wrong on that point.
01-11-2011, 02:18 PM   #13
Site Supporter
boriscleto's Avatar

Join Date: Dec 2009
Location: Liverpool, NY
Photos: Gallery
Posts: 12,309
QuoteOriginally posted by ryan s Quote
Does the K-x offer interchangeable screens? I was under the understanding it doesn't but I'd love to be proved wrong on that point.
Officially no. But they can be bought on the internet (Katzeye, Focusingscreen.com, etc.) and installed.
01-11-2011, 02:21 PM   #14
Pentaxian
ryan s's Avatar

Join Date: Jan 2008
Location: Madison, WI
Photos: Gallery
Posts: 2,370
Aha, nice! Maybe it's the older ones which didn't allow the user to change them (K100D, etc) without disassembling the camera...or maybe I just can't remember anything clearly

Using a darker *ist screen in mine helped the manual focusing immensely.
01-11-2011, 04:17 PM   #15
Site Supporter




Join Date: Nov 2008
Location: Singapore
Photos: Gallery
Posts: 904
QuoteOriginally posted by MSM Quote
I would look into a split prism. I know that the Kx is not supposed to have a changeable vf, but many here have done that. There are several threads here regarding the various makers and the way to change the vf screen. I used to have one for my k10. I found it to be more helpful than the magnifying eyecup.
The focusing screen of the K-x can be changed as I have done it before. I got mine from Focusing Screen. I bought the K3 version as it is bright enough
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!
beep, camera, couple, dslr, f2, focus, idea, lenses, photography, tamron
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Which prime lenses would work well? Vantage-Point Photographic Technique 9 11-08-2010 12:38 PM
Bag for Prime lenses? kpfeifle Pentax Camera and Field Accessories 6 06-19-2010 07:39 AM
Prime lenses ismaelg Troubleshooting and Beginner Help 11 04-30-2009 12:44 PM
Three quality prime lenses alexgn Pentax SLR Lens Discussion 25 07-19-2008 03:41 AM
Recommend Some Prime Lenses tux08902 Pentax SLR Lens Discussion 3 12-26-2007 11:43 AM



All times are GMT -7. The time now is 02:27 PM. | See also: NikonForums.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