Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
11-15-2015, 07:57 PM - 1 Like   #16
Senior Member




Join Date: Feb 2013
Photos: Gallery
Posts: 168
QuoteOriginally posted by Lowell Goudge Quote
What is your time worth to bastardiZe an old camera and cut t down to size. I doubt you are breaking even in the deal. My time is worth more than the $ 30 I spent so actually buying one has the chance of improving our economy by doing more valuable work
To put it simple: the time I spent doing this was priceless to me. Enjoy your GDP, in the meantime I'll continue to enjoy trying other stuff.

QuoteOriginally posted by excanonfd Quote
In a good light, half of the split prism does start blacking out but using the micro prisms encircling the split prism, I was able to get some acceptable shots but stacking multiple TC results in unacceptable loss of IQ which made that experiment redundant. Sorry, I lied it was f9.52 (or was it f10.36?) - Tamron Adaptall-2 300/2.8 + Pentax AFA 1.7x + Tamron 2x TC.
Seriously? Your F11-statement wasn't quite clear to me and it sounded rather surprising, so I asked.

I don't quite understand how I could have hurt so many people's feelings by talking about how much I enjoyed making a DIY split screen from a scrap camera and encourage other people to try it themselves. What's wrong with you, guys? If you love your Katzeye, that's great! What's your point other than pissing all over a nice DIY-thread?

11-16-2015, 07:49 AM   #17
New Member




Join Date: Apr 2015
Photos: Albums
Posts: 11
Original Poster
Interesting comments in the past days.
About the blackening: i`ve never, in about 40 film slr i`ve used, been able to focus down to f8 or even closed values. There are two reasons.
First: When aperture is constant, DOF at the focusing screen is always greater than DOF at the image plane, so even if things look sharp in the focusing screen, they might not be as well at the sensor plane. Second: when aperture is set at closed values (or with TCs, bellows, tubes), there`s not enough light passing in a good angle through all the oblique sides of the split prisms and microprism collar and total reflection occurs, thats an inherent behaviour of the arrangement of prisms used.
About individual desitions:
There are people who like to buy new things, and people who like to create. This post is about the possibilities of DIY; it is NOT about desitions, that`s a different discussion. But as this offtopic discussion arised, i would like to support my beliefs.
I see photography as a way to create and express emotion and ideas. The human character that makes it an art, is the thing that most easily fades away when cameras and lenses are treated just as a consumer product. If cutting your own screen makes you understand better the way images thake shape, it is a positive aspect, and it sure does help you in your photography praxis.
11-16-2015, 11:41 AM   #18
Pentaxian
jcdoss's Avatar

Join Date: Nov 2012
Location: Moving Soon
Photos: Gallery | Albums
Posts: 3,336
Just chiming in with an update on my situation. I purchased a scrap Super Program because I wanted to replace some parts on another camera I had already bought. After running across this thread, I figured, what the heck, let's pull out the focusing screen too, and put it in my K-x. The scrap camera showed up, I put batteries in it, and it's zinging along as good as or better than the one I wanted to fix. So, I'm not going to tear it up, and my quest continues for a "scrap" Super Program that is actually scrap. :-)
11-16-2015, 10:50 PM - 1 Like   #19
Otis Memorial Pentaxian
Loyal Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 41,553
QuoteOriginally posted by Bruno-C Quote
First: When aperture is constant, DOF at the focusing screen is always greater than DOF at the image plane, so even if things look sharp in the focusing screen, they might not be as well at the sensor plane.
How much so depends on the viewfinder magnification and how closely you are examining the image at the focal plane. At equal magnification (same apparent image size), the DOF should be the same for most vintage focus screens. The same is not true for the stock focus screens for most (all?) current model AF dSLR cameras across brands. Due to brightening tweaks, those screens show exaggerated DOF such that focus sensitivity is seldom better than about f/4 regardless of maximum aperture of the lens mounted.

Much also depends on the screen design. I have used full-matte screens optimized for fast lenses (so-called Canon S-type) that easily provide sufficient contrast and focus sensitivity to support lenses as fast as f/1.4.

QuoteOriginally posted by Bruno-C Quote
Second: when aperture is set at closed values (or with TCs, bellows, tubes), there`s not enough light passing in a good angle through all the oblique sides of the split prisms and microprism collar and total reflection occurs, thats an inherent behaviour of the arrangement of prisms used.
This is very true, though the point at which this happens depends on design of prism design. Most microprisms will black out badly at narrower than about f/4, but the better split image designs (e.g. KatzEye and Nikon K3) resist blackout to a little past f/8 while still providing adequate base length for excellent precision. (The prism is cut with a non-flat face.)


Steve

(Also been peering through SLR viewfinders for 45+ years...)


Last edited by stevebrot; 11-16-2015 at 10:57 PM.
11-17-2015, 04:57 PM   #20
Senior Member




Join Date: Feb 2013
Photos: Gallery
Posts: 168
QuoteOriginally posted by stevebrot Quote
Most microprisms will black out badly at narrower than about f/4, but the better split image designs (e.g. KatzEye and Nikon K3) resist blackout to a little past f/8 while still providing adequate base length for excellent precision. (The prism is cut with a non-flat face.)

Steve
Cool! This is something I didn't know (and couldn't have known fiddling around with cheap old scrap cameras) yet and most of all: it was presented in a civilized, informative manner that makes me want to keep on to broaden my horizon. Thanks for that!
11-24-2016, 11:50 AM   #21
New Member




Join Date: Nov 2016
Posts: 1
Hello all,

I'm really interested in cannibalizing a focusing screen with microprism from an old film SLR to use it in my DSLR.
However, i wonder if any focusing screen could be use with any DSLR...
Apart from the resizing process to use it with a viewfinder of a non-Full Frame DSLR, are there any other issues i should worry about ?
Idk, maybe the distance between the mirror and the focusing screen is probably not the same on FF SLR and an APS-C DSLR...

Thanks for your wisdom =)
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!
day, diy, focus, k-x, lenses, manual focus, pentax, screen, split-prism, tripod, video
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: KatzEye Split-Prism Focusing Screen - for K-3, K-5, K-5II, K-7, K-30, K-50 & K-500 Eyewanders Sold Items 7 04-15-2014 08:35 PM
Anybody want a free split-prism focusing screen for a K-x? ChopperCharles Pentax DSLR Discussion 6 06-03-2013 05:26 PM
For Sale - Sold: Pentax K-x w split prism focusing screen borysr Sold Items 2 12-09-2011 09:07 AM
For Sale - Sold: KatzEye Split Prism Focusing Screen for *istD/DS/DS2 (US) Julio Marcos Sold Items 3 08-06-2010 10:16 PM
For Sale - Sold: Split-Prism Focusing Screen for Cheap SOldBear Sold Items 4 03-11-2009 02:52 PM



All times are GMT -7. The time now is 11:30 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