Setting Focus on Ground Glass

Mitchell Lewis · February 12th, 2009, 01:56 PM

I've shot about 6 different projects since I originally put together our camera rig (EX3 and Letus Ultimate). When I focused the EX3 lens on the Letus Ultimate ground glass, I thought it was interesting that the focus was bottomed out. In other words, it was at the maximum setting for close focus.

Last week I removed the Ultimate and did some shooting without it (I haven't worked on that project yet for a comparison). But last night I had to reinstall the Ultimate for another project. When I set the focus I spent a lot more time to try and get it absolutely perfect. This yielded a slight different focus setting (it wasn't bottomed out this time) and this morning I've been looking at my footage and it's definitely sharper than what I had shot previously.

I'm thrilled! That was one of my complaints about the Ultimate was that all my footage looked slightly soft. No one else ever noticed it, but I did. But now my recent footage looks sharp as a tack. I can only dream of what the new Letus EX3 relay lens will do for sharpness (I've heard it makes your footage even sharper). Hopefully it's not as expensive as their B4 adaptors they released recently.

The point is, make sure to triple-check the focus on your ground glass. And then keep an eye on it while you're installing your gaffers tape (to keep the focus from moving). Make sure it doesn't moving while your installing the tape.

Ola Christoffersson · February 13th, 2009, 02:11 PM

You are right that focus on the GG is absolutely critical. I have two pieces of advice on this topic.

1. Don't set focus on the groundglass only. Use a focus chart (like the one included in the Letus manual) to fine tune your focus on. I have found that simply focusing on the ground glass does not necesseraly give exact focus.

2. I have not heard about anybody else doing this but I use the cameras A/B-memory buttons to store focus and zoom settings. Once I am happy about the focus I store the setting on both memorys. I then put gaffers tape on the focus reel. After doing that I can make sure I it has not moved by recalling either memory.

Keith Moreau · February 13th, 2009, 03:34 PM

So Olaf, you're saying the true focus point is somewhere other than the ground glass 'grain'. It's pretty easy to focus on that but it's good to know that the focal point isn't necessarily there.

Memory settings imply using the AF/MF mode to allow the servo to control the focus, which many people don't ever set, so this is good to know too.

February 12th, 2009, 01:56 PM	#1
Mitchell Lewis Trustee Join Date: Dec 2008 Location: Kennewick, WA Posts: 1,124	Setting Focus on Ground Glass - CRITICAL I've shot about 6 different projects since I originally put together our camera rig (EX3 and Letus Ultimate). When I focused the EX3 lens on the Letus Ultimate ground glass, I thought it was interesting that the focus was bottomed out. In other words, it was at the maximum setting for close focus. Last week I removed the Ultimate and did some shooting without it (I haven't worked on that project yet for a comparison). But last night I had to reinstall the Ultimate for another project. When I set the focus I spent a lot more time to try and get it absolutely perfect. This yielded a slight different focus setting (it wasn't bottomed out this time) and this morning I've been looking at my footage and it's definitely sharper than what I had shot previously. I'm thrilled! That was one of my complaints about the Ultimate was that all my footage looked slightly soft. No one else ever noticed it, but I did. But now my recent footage looks sharp as a tack. I can only dream of what the new Letus EX3 relay lens will do for sharpness (I've heard it makes your footage even sharper). Hopefully it's not as expensive as their B4 adaptors they released recently. The point is, make sure to triple-check the focus on your ground glass. And then keep an eye on it while you're installing your gaffers tape (to keep the focus from moving). Make sure it doesn't moving while your installing the tape. __________________ Sony EX3, Canon 5D MkII, Chrosziel Matte Box, Sachtler tripod, Steadicam Flyer, Mac Pro, Apple/Adobe software - 20 years as a local videographer/editor

February 13th, 2009, 02:11 PM	#2
Ola Christoffersson Major Player Join Date: Nov 2007 Location: Stockholm, Sweden Posts: 462	You are right that focus on the GG is absolutely critical. I have two pieces of advice on this topic. 1. Don't set focus on the groundglass only. Use a focus chart (like the one included in the Letus manual) to fine tune your focus on. I have found that simply focusing on the ground glass does not necesseraly give exact focus. 2. I have not heard about anybody else doing this but I use the cameras A/B-memory buttons to store focus and zoom settings. Once I am happy about the focus I store the setting on both memorys. I then put gaffers tape on the focus reel. After doing that I can make sure I it has not moved by recalling either memory. __________________ Ola Christoffersson, Kamrat produktion, Stockholm - Sweden www.kamrat.tv

February 13th, 2009, 03:34 PM	#3
Keith Moreau Major Player Join Date: Nov 2006 Location: Brisbane, California Posts: 530	So Olaf, you're saying the true focus point is somewhere other than the ground glass 'grain'. It's pretty easy to focus on that but it's good to know that the focal point isn't necessarily there. Memory settings imply using the AF/MF mode to allow the servo to control the focus, which many people don't ever set, so this is good to know too.