eyepiece magnifier
Posted 04/10/2010 - 19:56
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I think Algi was meaning the 2x aspect rather than the right-angled aspect. Obviously, one of the straight magnifiers (or the appropriate viewfinder on my LX) would do just as well.
K.
K.
Kris Lockyear
It is an illusion that photos are made with the camera… they are made with the eye, heart and head. Henri Cartier-Bresson
Lots of film bodies, a couple of digital ones, too many lenses (mainly older glass) and a Horseman LE 5x4.
It is an illusion that photos are made with the camera… they are made with the eye, heart and head. Henri Cartier-Bresson
Lots of film bodies, a couple of digital ones, too many lenses (mainly older glass) and a Horseman LE 5x4.
Posted 04/10/2010 - 20:32
Link
The Refconverter is the highest quality magnifier that Pentax make. I've not tried any of the Seagull 2.6x magnifiers, they would be handy if they are better. I've only ever used the Spotmatic 2x straight magnifier and it was very poor. I've not tried the latest version (£69 I think).
With a 2x Refconverter 'A' used for testing lenses say 50mm f/1.4 at 25x focal length I can usually get 1 out of 4 shots in focus. This is a semi-statistical distribution and will have included for any error in the position of the focus screen. I've never tried it with live view, but I'm happy with 1 in 4. I just look at the 4 shots in browser and pick the best.
At f/5.6 nearly every shot will be in focus because of DOF. Some lenses shift focus on stopping down, but this seems to be within the DOF.
This page Focus Fallibility: Lens Test Fallacies explains some of the problems encountered with focusing for lens testing purposes.
With a 2x Refconverter 'A' used for testing lenses say 50mm f/1.4 at 25x focal length I can usually get 1 out of 4 shots in focus. This is a semi-statistical distribution and will have included for any error in the position of the focus screen. I've never tried it with live view, but I'm happy with 1 in 4. I just look at the 4 shots in browser and pick the best.
At f/5.6 nearly every shot will be in focus because of DOF. Some lenses shift focus on stopping down, but this seems to be within the DOF.
This page Focus Fallibility: Lens Test Fallacies explains some of the problems encountered with focusing for lens testing purposes.
Half Man... Half Pentax ... Half Cucumber
Pentax K-1 + K-5 and some other stuff
Algi
Pentax K-1 + K-5 and some other stuff
Algi
Posted 05/10/2010 - 14:43
Link
I've tried film 3 cameras with split image screens (Pentax MX, Olympus OM20, Chinon CE-5) with 50mm f/1.4 lenses by standing in front of a door focusing on the vertical edge (door to architrave gap) at eye level then moving up and down the door and watching the split image. It only moves off-line close to the bottom of the door, so I don't think it's very accurate.
The microprisms surrounding the split image on the Chinon are quite impressive though, they do shimmer when the split image looks in line and it looks more accurate. Unfortunately it's not an interchangeable screen. I might see if I can get it out and adapt it to a K20D.
The microprisms surrounding the split image on the Chinon are quite impressive though, they do shimmer when the split image looks in line and it looks more accurate. Unfortunately it's not an interchangeable screen. I might see if I can get it out and adapt it to a K20D.
Half Man... Half Pentax ... Half Cucumber
Pentax K-1 + K-5 and some other stuff
Algi
Pentax K-1 + K-5 and some other stuff
Algi
Posted 05/10/2010 - 16:21
Link
The usual split prism screens ( either cheap ebay or more expensive Katzeye ones) have a microprism collar around the split prism, just like my old MX film camera.
If you dont have a suitable vertical line to check focus with, the collar works just as well (if not better).
I tend to focus manually most of the time and my cheap chinese made split prism/microprism collar screen gives me spot on accuracy 100% of the time
If you dont have a suitable vertical line to check focus with, the collar works just as well (if not better).
I tend to focus manually most of the time and my cheap chinese made split prism/microprism collar screen gives me spot on accuracy 100% of the time
Peter
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6724 posts
20 years
Glasgow,
Scotland
The reason that more of your photos are now in focus Kris is that they are within the DOF which is fair enough. Anything requiring exact focus would need a 2x Refconverter and focus on the screen. Just do the focus test on a door to see what I mean.
A good tip for focusing on the screen is to focus on some lettering, if you can't read it.... it isn't in focus
“We must avoid however, snapping away, shooting quickly and without thought, overloading ourselves with unnecessary images that clutter our memory and diminish the clarity of the whole.” - Henri Cartier-Bresson -