Medium format Questions at DVinfo.net

Aaron Shaw · January 4th, 2005, 09:30 PM

Hi guys,

I have a few questions about medium format lenses which I hope you can help me with:

1) How far back should I place my ground glass from the rear of my lens? I'm using Kiev 88 MF lenses.

2) Has anyone found a GG that is larger than 50mm in diameter? It would be great if I could find one in a 72mm threaded mount.

3) Anyone have a good idea on how to go about home threading the ends of a piece of PVC pipe? For that matter, does anyone know where I can get 3" diameter PVC pipe?

Brett Alan · January 5th, 2005, 01:42 AM

Shaw I've been watching a lot of your post and I admire your hard work and dedication to this project but damn man you gotta do a little researching before you ask these questions. Most of this stuff is easy to find or find out.

1)Set your lens to its minimum focus and widest aperature. Place a object in front of it that exact distance away and then move the GG until its in focus. Thats the distance your looking for.

2)MF ground glass

3)Home Depot or any other major hardware store. I wouldnt recomend using PVC though - that is if your planing to thread it to make a focusing tube. The threads will be too fine for plastic to work properly for this purpose.

Aaron Shaw · January 5th, 2005, 10:31 AM

Hi Brett. Quite right! I suppose I should clarify though - it's not so bad actually:

1) I don't have a lens at the moment. Just sent in an order and didn't want to wait for the item to be shipped to continue working on my adapter.

2) I'm not sure that MF ground glass would work. It's usually lined and I'm not sure that the size is actually large enough for the true projected image as the light is fed through (I think) a prism before hitting the ground glass focusing screen. I know the focusing screen on most 35mm cameras isn't large enough for the true 35mm image.

3) Excellent point about the threading. I did take a look at home depot but couldn't find anything even remotely large enough. They must have something but I honestly could not find it!

John Nagle · January 5th, 2005, 11:53 AM

Aaron,
I don’t think threading would work on pvc but there are other plastic compounds that can be threaded and would not be any heavier. If you know anyone who works with plastics maybe they could suggest an alternate material.

With regards to a GG I found a web page about a guy who made a static adapter, the company he bought the GG from could do something big enough for MF as well.

From his description the screen give no problems with hotspot or grain.

The first link is to his site and the second is to the screen manufacturer.

http://www.blindcat.de/commentcreate.php?page=dv35genglish&title=DV35g%20-%20A%2035mm%20Adapter&parent=dv35g

http://www.glasscreen.com/

January 4th, 2005, 09:30 PM	#1
Aaron Shaw Major Player Join Date: Jul 2004 Posts: 587	Medium format Questions Hi guys, I have a few questions about medium format lenses which I hope you can help me with: 1) How far back should I place my ground glass from the rear of my lens? I'm using Kiev 88 MF lenses. 2) Has anyone found a GG that is larger than 50mm in diameter? It would be great if I could find one in a 72mm threaded mount. 3) Anyone have a good idea on how to go about home threading the ends of a piece of PVC pipe? For that matter, does anyone know where I can get 3" diameter PVC pipe?

January 5th, 2005, 01:42 AM	#2
Brett Alan New Boot Join Date: Dec 2004 Location: Anaheim, CA Posts: 16	Shaw I've been watching a lot of your post and I admire your hard work and dedication to this project but damn man you gotta do a little researching before you ask these questions. Most of this stuff is easy to find or find out. 1)Set your lens to its minimum focus and widest aperature. Place a object in front of it that exact distance away and then move the GG until its in focus. Thats the distance your looking for. 2)MF ground glass 3)Home Depot or any other major hardware store. I wouldnt recomend using PVC though - that is if your planing to thread it to make a focusing tube. The threads will be too fine for plastic to work properly for this purpose.

January 5th, 2005, 10:31 AM	#3
Aaron Shaw Major Player Join Date: Jul 2004 Posts: 587	Hi Brett. Quite right! I suppose I should clarify though - it's not so bad actually: 1) I don't have a lens at the moment. Just sent in an order and didn't want to wait for the item to be shipped to continue working on my adapter. 2) I'm not sure that MF ground glass would work. It's usually lined and I'm not sure that the size is actually large enough for the true projected image as the light is fed through (I think) a prism before hitting the ground glass focusing screen. I know the focusing screen on most 35mm cameras isn't large enough for the true 35mm image. 3) Excellent point about the threading. I did take a look at home depot but couldn't find anything even remotely large enough. They must have something but I honestly could not find it!

January 5th, 2005, 11:53 AM	#4
John Nagle Regular Crew Join Date: Nov 2004 Posts: 28	Aaron, I don’t think threading would work on pvc but there are other plastic compounds that can be threaded and would not be any heavier. If you know anyone who works with plastics maybe they could suggest an alternate material. With regards to a GG I found a web page about a guy who made a static adapter, the company he bought the GG from could do something big enough for MF as well. From his description the screen give no problems with hotspot or grain. The first link is to his site and the second is to the screen manufacturer. http://www.blindcat.de/commentcreate.php?page=dv35genglish&title=DV35g%20-%20A%2035mm%20Adapter&parent=dv35g http://www.glasscreen.com/