Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
03-26-2009, 11:48 PM   #1
Veteran Member
milesy's Avatar

Join Date: Jan 2009
Location: Melbourne
Photos: Gallery
Posts: 379
Another Focus Screen Question

HI All

sorry to raise yet another question on focus screens but i need some advise.

I bought one of the cheapo chinese Split Prism focus screens and fitted it no problem. I am however having some trouble using it on my 300mm zoom lense. As in when i focus and it looks good, when i load the pics on the PC they are out of focus.

My lense is a Sigma 28-300 3.5-6.3 lense. i took some pics last night and certainly wide open with a flash the screen shows me sharp images just where i expect them however with the lense zoomed right out - i seem to have some problems.

Can someone also explain (im sure someone already has but i just cant find it) what the use of the micro prisms around the outside are for - these seem a bit useless to me

thanks

Adrian

03-27-2009, 12:02 AM   #2
Veteran Member




Join Date: Jan 2009
Location: Canada
Posts: 1,255
QuoteOriginally posted by milesy Quote
HI All

sorry to raise yet another question on focus screens but i need some advise.

I bought one of the cheapo chinese Split Prism focus screens and fitted it no problem. I am however having some trouble using it on my 300mm zoom lense. As in when i focus and it looks good, when i load the pics on the PC they are out of focus.

My lense is a Sigma 28-300 3.5-6.3 lense. i took some pics last night and certainly wide open with a flash the screen shows me sharp images just where i expect them however with the lense zoomed right out - i seem to have some problems.

Can someone also explain (im sure someone already has but i just cant find it) what the use of the micro prisms around the outside are for - these seem a bit useless to me

thanks

Adrian
You may need a different shim. Paper cutouts work.

The microprisms are useful when you have nothing to line up.
03-27-2009, 12:20 AM   #3
Veteran Member
milesy's Avatar

Join Date: Jan 2009
Location: Melbourne
Photos: Gallery
Posts: 379
Original Poster
forgot to mention this is on an IST DS body
03-27-2009, 12:45 AM   #4
Veteran Member
RawheaD's Avatar

Join Date: Dec 2008
Location: MA, USA
Photos: Gallery
Posts: 831
mechanically speaking, the problem cannot be limited to the tele end of your zoom. I.e., if the cam has a front/back focus issue, it's always going to have it, regardless of the focal length. It may seem more pronounced on the tele-end, and that might be what you're seeing.

Anyway, I just went through this problem with a KatzEye, and in the end, ended up sending my K20D to KatzEye and had them do the calibration. Cost a few dozen clams, and was worth every penny. My MF focuses are now BANG on every time.


And I even have a cat's eye to prove it :-D








With the el-cheapo, I think the only option you have is to do it yourself. You order a set of differnt thickness shims from Pentax (very cheap for a set of 12 or so, I think), and you keep trying on different ones till you get the focus right.


You *could* try getting Pentax to do it (not with the 3rd party screen, though, obviously) but I'll forewarn you; I sent my K20D still under warranty to Colorado, included very detailed test results and eplained in detail I had a severe MF frontfocus issue and kindly asked to get it fixed.

The cam came back 2 weeks later, and NOTHING about my MF was fixed. Instead, they threw in a copy of a page out of the manual explaining how I can set the body to compentate for FF/BF issues for *AF*. Stupid Sexy Pentax.

03-27-2009, 01:46 AM   #5
Veteran Member
milesy's Avatar

Join Date: Jan 2009
Location: Melbourne
Photos: Gallery
Posts: 379
Original Poster
ive been playing around a bit with the focus both manual and auto, and yes when the camera thinks the image is in focus i get a fairly sharp photo. However at that point the image in the split has the bottom half slight to the right of the top.

Given this - it sort of indicates that the focus screen needs a little movement, however how do i know if it needs to move front or back??
03-27-2009, 01:57 AM   #6
Veteran Member
milesy's Avatar

Join Date: Jan 2009
Location: Melbourne
Photos: Gallery
Posts: 379
Original Poster
or maybe its the placement of my eye on the viewfinder - i ssem to be able to change the split slighty by moving my eye??
03-27-2009, 03:59 AM   #7
Veteran Member
milesy's Avatar

Join Date: Jan 2009
Location: Melbourne
Photos: Gallery
Posts: 379
Original Poster
still playing around - it seems that i had to adjust the diopter adjustment all the way to one end - now the manual focus seems to agree more with the AF.........
03-27-2009, 05:19 AM   #8
Veteran Member
Matjazz's Avatar

Join Date: Sep 2006
Location: EU/Slovenia
Photos: Gallery
Posts: 774
QuoteOriginally posted by RawheaD Quote
With the el-cheapo, I think the only option you have is to do it yourself. You order a set of differnt thickness shims from Pentax (very cheap for a set of 12 or so, I think), and you keep trying on different ones till you get the focus right.
That's good news for me. Not only to tweak ebay focusing screens but factory ones as well. I'm writing an email to my local dealer already.

03-27-2009, 07:05 AM   #9
Site Supporter
Site Supporter




Join Date: Jul 2008
Location: Cleveland, OH, USA
Photos: Gallery
Posts: 261
Hi Adrian,
As others suggested, it looks like a problem with position of the focusing screen. I had this issue when I put Katzeye in my cam. The general approach to resolve it is this.
Do 45deg picture of a ruler to determine if it's back- or front focus; use the fastest lens you have wide open.
Depending on FF or BF put thicker or thinner shim behind the focusing screen.
Unfortunately, that's the price of those chineese focusing screens: I went with the Katzeye, paid x5 but Rachael Katz(owner) took care of the problem.
Good luck,
03-27-2009, 08:51 AM   #10
Site Supporter
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 27,663
In regards to your second question...

Split-image vs. Micro-prism Compare and Contrast
  • Split image excels when a hard line is present in the subject
  • Micro-prism excels when texture is present on the subject
  • Split-image is pretty much useless without a hard line
  • Micro-prism can be used on subjects lacking texture but having a hard line
  • When neither a hard-line nor texture is present, but systems are useless
Back in the "old" days, cameras would come with either a split-image or a micro-prism focus screen. Sometime in the late 70s, the split-image with micro-prism donut became popular as a compromise. I personally prefer the plain micro-prism, but good luck on finding that option today!

Steve
03-27-2009, 08:52 AM   #11
Veteran Member
deejjjaaaa's Avatar

Join Date: May 2007
Location: steel city / rust belt
Posts: 2,046
QuoteOriginally posted by sinus007 Quote
Unfortunately, that's the price of those chineese focusing screens
you just need to buy the right focusing screens - they are different... I have two cut from Minolta X700 OEMs and they do not require any shims (have them in K20D and *istDL)... ebay seller cowy07

the ones cut from Pentax K1000 OEMs (jinfinance) indeed require shims, I had it too once w/ my K10D, it worked properly w/ shim supplied by the seller, sold it installed w/ the camera.
03-27-2009, 09:01 AM   #12
Veteran Member
deejjjaaaa's Avatar

Join Date: May 2007
Location: steel city / rust belt
Posts: 2,046
QuoteOriginally posted by stevebrot Quote
I personally prefer the plain micro-prism, but good luck on finding that option today!

interested parties should monitor Focusing Screen - they run out of stock of those screens (cut from Canon Ec-A) only ~4 weeks ago - good chance that they will have new stock soon
03-27-2009, 09:37 AM   #13
Veteran Member
Jewelltrail's Avatar

Join Date: May 2008
Location: Rhode Island
Photos: Albums
Posts: 4,180
Some help on screens

For months now, I have been carefully following our forum threads on the Chinese screens. Often, confusion arises concerning the screens. There are at least 2 sources for the confusion.

Firstly, the K10d, K20d & IST do not use shims and can be bought here: Diagonal Split Image Focus Screen 4 Pentax k10D k20D DS - eBay (item 110317645411 end time Apr-24-09 10:44:46 PDT) This is the seller I used--there are plenty of other options too. I like jinfinance because you can ask a question and he'll answer it. Perhaps the other sellers do too--I do not know. Other Pentax cameras do you shims--so it is necessary you purchase the correct screen.

Secondly, the K100d/K200d screen is a little larger than the K10/K20 screen. Jinfinance is aware of this difference. If you read below, you will see a customer/seller interaction which highlights a very important distinction between these differing Pentax screens. What can happen, unfortunately, is a buyer can unknowingly by the larger screen and then try and force it into the smaller focus frame screen of the K10/K20 setup. Of course, the reverse scenario can occur too. I read a post where a very unhappy buyer (fellow forum member) ran into this. I do not know if it was the fault of the seller, or of the buyer, but these problems can be avoided if you do a little question and answer thing with the seller, before you buy.

Below is an example of what I mean. In blue is the buyer, along with their question. The red words are seller. I post this to illustrate the vital need for interaction in a sale of this kind between buyer and seller. Also, and finally, the K10/K20/ist do not use shims. I you are shimming one of these camera with a screen something is wrong.




Q: I have both the K100D and K20D Pentax dSLR cameras. I want a split focus screen for the K20D (but would also like to try it in the K100D). Other vendors sell a focus screen that fits both the K100D and K20D camera (in fact they claim it fits K100D, K200D, K10D and K20D cameras). Can you explain this to me - what are the exact dimensions (including depth) of the split focus screens you sell for the K100D and K20D cameras?

Mar-19-09
A: thanks for the message... unfortunately, K100D/K200D uses a different sized (a little larger) screen than K10D/K20D... the thickness (depth?) is the same though... so in theory, you can try to use the screen for K10D/K20D, and install it with K100D/K200D body.. but it might wobble (because it's smaller than it should be) and might cause trouble... best...

Edit Another source for confusion is the fact the Pentax camera models are so close in names. For example, K20/K200 & K10/K100--it is no wonder problems are common, especially if you rush your order--so many people are in a hurry. Be careful--best of luck to everyone.
03-27-2009, 10:25 AM   #14
Veteran Member
deejjjaaaa's Avatar

Join Date: May 2007
Location: steel city / rust belt
Posts: 2,046
QuoteOriginally posted by Jewelltrail Quote
For months now, I have been carefully following our forum threads on the Chinese screens. Often, confusion arises concerning the screens. There are at least 2 sources for the confusion.

Firstly, the K10d, K20d & IST do not use shims and can be bought here: Diagonal Split Image Focus Screen 4 Pentax k10D k20D DS - eBay (item 110317645411 end time Apr-24-09 10:44:46 PDT) This is the seller I used--there are plenty of other options too. I like jinfinance because you can ask a question and he'll answer it. Perhaps the other sellers do too--I do not know. Other Pentax cameras do you shims--so it is necessary you purchase the correct screen.
may be jinfinance has changed the OEM - I had his screen in K10D in 2008 (diagonal split prism, cut from K1000) and it required a shim, supplied by jinfinance
03-27-2009, 12:52 PM   #15
Veteran Member
Jewelltrail's Avatar

Join Date: May 2008
Location: Rhode Island
Photos: Albums
Posts: 4,180
QuoteQuote:
deejjjaaaa: may be jinfinance has changed the OEM - I had his screen in K10D in 2008 (diagonal split prism, cut from K1000) and it required a shim, supplied by jinfinance
Okay, now the permutations for getting the wrong screen are really getting complex. Thanks deejjjaaaa! Hopefully, by posting all this, future buyers will have what they need to make informed decisions.
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, focus, focus screen, lense, photography, pics, question, screen, screens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
K-x focus screen drawing & Travor focus screen issue xjx Pentax DSLR and Camera Articles 2 06-06-2012 10:13 PM
focus screen and fungus question slow2focus Pentax DSLR Discussion 4 05-07-2010 10:10 PM
yet another focus screen question slow2focus Pentax Camera and Field Accessories 8 01-26-2010 09:07 PM
Quick Question: Pentax KM screen replaceable with split-focus screen? vinzer Pentax Film SLR Discussion 2 01-06-2009 01:21 AM
focus screen question perstephone6 Pentax DSLR Discussion 4 09-03-2008 12:24 PM



All times are GMT -7. The time now is 02:24 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