01-20-2012, 05:03 PM
[quote name='IanCD' timestamp='1327018227' post='15046']
Nice thread VL..! <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='
' />
(Re-) learning as I am, I haven't been using MF at all over the last year... but I do (vaguely) remember how useful I used to find the split (45 degree) prism...
So, Wim, that looks a useful link, but I'm wondering, why the laser matte screen rather than one with a split prism...? What does it add to what you get through a 'normal' (AF) OVF..? Did I miss something..?
Ian
[/quote]
A normal focusing screen, especially for digital, has a fairly coarse matting. One could say that this matting really determines the CoC for the image seen on the focusing screen or in the view finder; the coarser the matting is, the larger this CoC becomes, and the more apparent DoF you will see. An average dslr focusing screen will show a DoF which is similar to about F/5.6 to start with, almost independent of the lens used. In order to focus with a lens set to a larger aperture, is going to be rather difficult IOW, which means one either has to rely on focus confirmation, which generally doesn't work too well with lenses built for AF with their very short focusing throws, or on LiveView.
So, in comes the laser precision matte, with a very, very fine matting, and hence a very small virtual CoC, allowing one to see DoF more or less properly. The disadvantage of these screens is that the fine matting also causes a lot of light to be reflected, and hence the image gets a little darker. I have never found this to be a problem yet, however. I even use it to manually focus my MP-E 65 at 5X magnification without a problem without any extra illumination, or my 100-400L at 400 mm and F/5.6 in dim light without a problem.
As to split prisms: they suffer IMO from the same problem as the focus confirm option: it is very difficut to focus correctly, because it is easy to go past the focus point with the short throw of modern AF lenses. It even is difficult when using an old fashioned lens. Also, the wedge always is centered in the frame, which means one needs to adjust focus for recompostion after focusing anyway, where one again tends to have an F/5.6 matte, and this is where the laser matte really shines: it allows one to MF on any part of the screen, at least in my experience.
I have been using these screens for a long time already. I think I mentioned I had/have one on my Pentax MX, which dates all the way back to 1979 <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='
' />.
BTW, with film this was easier, because film has inherently more wiggling room than digital, due to the thickness of the film emulsion <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='' />.
Kind regards, Wim
Nice thread VL..! <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='
' />(Re-) learning as I am, I haven't been using MF at all over the last year... but I do (vaguely) remember how useful I used to find the split (45 degree) prism...
So, Wim, that looks a useful link, but I'm wondering, why the laser matte screen rather than one with a split prism...? What does it add to what you get through a 'normal' (AF) OVF..? Did I miss something..?
Ian
[/quote]
A normal focusing screen, especially for digital, has a fairly coarse matting. One could say that this matting really determines the CoC for the image seen on the focusing screen or in the view finder; the coarser the matting is, the larger this CoC becomes, and the more apparent DoF you will see. An average dslr focusing screen will show a DoF which is similar to about F/5.6 to start with, almost independent of the lens used. In order to focus with a lens set to a larger aperture, is going to be rather difficult IOW, which means one either has to rely on focus confirmation, which generally doesn't work too well with lenses built for AF with their very short focusing throws, or on LiveView.
So, in comes the laser precision matte, with a very, very fine matting, and hence a very small virtual CoC, allowing one to see DoF more or less properly. The disadvantage of these screens is that the fine matting also causes a lot of light to be reflected, and hence the image gets a little darker. I have never found this to be a problem yet, however. I even use it to manually focus my MP-E 65 at 5X magnification without a problem without any extra illumination, or my 100-400L at 400 mm and F/5.6 in dim light without a problem.
As to split prisms: they suffer IMO from the same problem as the focus confirm option: it is very difficut to focus correctly, because it is easy to go past the focus point with the short throw of modern AF lenses. It even is difficult when using an old fashioned lens. Also, the wedge always is centered in the frame, which means one needs to adjust focus for recompostion after focusing anyway, where one again tends to have an F/5.6 matte, and this is where the laser matte really shines: it allows one to MF on any part of the screen, at least in my experience.
I have been using these screens for a long time already. I think I mentioned I had/have one on my Pentax MX, which dates all the way back to 1979 <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='
' />.BTW, with film this was easier, because film has inherently more wiggling room than digital, due to the thickness of the film emulsion <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='
' />.Kind regards, Wim
Gear: Canon EOS R with 3 primes and 2 zooms, 4 EF-R adapters, Canon EOS 5 (analog), 9 Canon EF primes, a lone Canon EF zoom, 2 extenders, 2 converters, tubes; Olympus OM-D 1 Mk II & Pen F with 12 primes, 6 zooms, and 3 Metabones EF-MFT adapters ....