When focusing on infinity...?

Leo Mandy · February 15th, 2005, 05:12 PM

Ok, so no help there I guess. Darn it! I want to set this exact!

Leo Mandy · February 15th, 2005, 09:17 PM

Ok, so now I am really confused on this FOCUS TO INFINITY mechanics :

http://dvstuff.250free.com

Here is what I did. I took my DV cam out of the equation, using only a magnifying glass and the GG, I zoomed out to 105mm at inifinity on my SLR - then I adjusted my GG to focus in properly. Came in clear - see first picture.
Now in my experience, if you focus on infinity, you zoom in and focus - when you zoom out, even else is in focus as well. Not so with this : seem picture 2.
In picture 2, I zoomed back out to 35mm, leaving the rubberized part on infinity. Blurry and unuseable!
I am guessing the SLR work different than TV cameras?

Also - I had to institute the DV camera to take these shots - but even without it, using only the magnifying glass agains the GG - the 35mm at infinity is not sharp at all.

Does anyone know what is going on?

Leo Mandy · February 16th, 2005, 06:58 AM

Ok, after thinking about it last night - I am mixing about zoom/focus to infinity with Focal Range. Ok, got it. Now I can move on.

Leo Mandy · February 16th, 2005, 03:23 PM

When calculate for focus length-

1) do you measure from the front lens to the object

2) or do you measure from the back of the lens to the object

3) Or do you measure from the GG to the object

Thanks

Mark Kubat · February 16th, 2005, 07:02 PM

Mandy, if I remember correctly, your focal plane should be where focused ie. GG so should measure from GG when it's in the right place... On movie sets when they measure focal distance, they don't measure from end of lens - there's a line on the camera body indicating where the focal plane is "inside" the camera and focus measurements are taken from that marker...

Quick question since I'm new to all this - does field of view when you build this and film with vidcam via macro pretty much match what you see if you just have your lens attached to SLR camera body and look through eyepiece? Ie. does lens on SLR body work effectively as "director's viewfinder" or does the ballgame change drastically once lens is on adaptor? I think it should be the same, right?

Oscar Spierenburg · February 16th, 2005, 07:25 PM

Mark,
it should be the same, but only if you have the light well spread on the GG. Otherwise you'll have to zoom in on the GG to get rid of the dark edges.
I'm thinking of taking apart a photo camera and cut off all but the lens mount and the eyepiece to use it as a directors viewfinder ánd a separate attachable viewfinder on the adapter.
But maybe I'll build it with spare parts.

Mark Kubat · February 16th, 2005, 07:31 PM

Just visited your site and saw your chart/couch tests for infinity - remember that Mediachance recommends focusing on something "far away." I'm wondering if you're too close to your focus reference object (ie. chart) for it to work right? Infinity is supposed to be far away...

I dunno. I'll be doing this tomorrow, so I guess I'll report then!

Good luck!

Leo Mandy · February 16th, 2005, 08:01 PM

I stupidly, yes stupidly assumed that infinity would be ok at 3 meters. My bad, my mistake. Taking Jonathon advice, I measured out 1.6 meters at 105mm - which is the nearest point on my SLR and focused to that on the chart (which works great). It now looks better and seems to focus alright. I won't be able to really tell until the MACRO filter that I ordered comes in - called today and still not there!

Right now I am trying something new. I have tried the Tracing Paper route - and mine is too thick. Nice picture from the GG, but too dark. I need a light grade or gauge. Still looking - but what I did was this :

I sprayed the CD with Spray glue and then looked at it - my goodness, doesn't it look like a frosted CD with just the glue on it? Going to run some test when it dries to see if this is another viable option.

Mark, good on you! Keep me posted on your progress.

February 16th, 2005, 07:02 PM	#35
Mark Kubat Major Player Join Date: Jan 2003 Location: Toronto, Canada Posts: 375	technically, the focal plane... Mandy, if I remember correctly, your focal plane should be where focused ie. GG so should measure from GG when it's in the right place... On movie sets when they measure focal distance, they don't measure from end of lens - there's a line on the camera body indicating where the focal plane is "inside" the camera and focus measurements are taken from that marker... Quick question since I'm new to all this - does field of view when you build this and film with vidcam via macro pretty much match what you see if you just have your lens attached to SLR camera body and look through eyepiece? Ie. does lens on SLR body work effectively as "director's viewfinder" or does the ballgame change drastically once lens is on adaptor? I think it should be the same, right?

February 16th, 2005, 07:31 PM	#37
Mark Kubat Major Player Join Date: Jan 2003 Location: Toronto, Canada Posts: 375	Mandy, here's a thought? Just visited your site and saw your chart/couch tests for infinity - remember that Mediachance recommends focusing on something "far away." I'm wondering if you're too close to your focus reference object (ie. chart) for it to work right? Infinity is supposed to be far away... I dunno. I'll be doing this tomorrow, so I guess I'll report then! Good luck!

February 15th, 2005, 05:12 PM	#31
Leo Mandy Major Player Join Date: Dec 2004 Posts: 749	Ok, so no help there I guess. Darn it! I want to set this exact!

February 15th, 2005, 09:17 PM	#32
Leo Mandy Major Player Join Date: Dec 2004 Posts: 749	Ok, so now I am really confused on this FOCUS TO INFINITY mechanics : http://dvstuff.250free.com Here is what I did. I took my DV cam out of the equation, using only a magnifying glass and the GG, I zoomed out to 105mm at inifinity on my SLR - then I adjusted my GG to focus in properly. Came in clear - see first picture. Now in my experience, if you focus on infinity, you zoom in and focus - when you zoom out, even else is in focus as well. Not so with this : seem picture 2. In picture 2, I zoomed back out to 35mm, leaving the rubberized part on infinity. Blurry and unuseable! I am guessing the SLR work different than TV cameras? Also - I had to institute the DV camera to take these shots - but even without it, using only the magnifying glass agains the GG - the 35mm at infinity is not sharp at all. Does anyone know what is going on?

February 16th, 2005, 06:58 AM	#33
Leo Mandy Major Player Join Date: Dec 2004 Posts: 749	Ok, after thinking about it last night - I am mixing about zoom/focus to infinity with Focal Range. Ok, got it. Now I can move on.

February 16th, 2005, 03:23 PM	#34
Leo Mandy Major Player Join Date: Dec 2004 Posts: 749	When calculate for focus length- 1) do you measure from the front lens to the object 2) or do you measure from the back of the lens to the object 3) Or do you measure from the GG to the object Thanks

February 16th, 2005, 07:25 PM	#36
Oscar Spierenburg Major Player Join Date: Jan 2005 Location: (The Netherlands - Belgium) Posts: 735	Mark, it should be the same, but only if you have the light well spread on the GG. Otherwise you'll have to zoom in on the GG to get rid of the dark edges. I'm thinking of taking apart a photo camera and cut off all but the lens mount and the eyepiece to use it as a directors viewfinder ánd a separate attachable viewfinder on the adapter. But maybe I'll build it with spare parts.

February 16th, 2005, 08:01 PM	#38
Leo Mandy Major Player Join Date: Dec 2004 Posts: 749	I stupidly, yes stupidly assumed that infinity would be ok at 3 meters. My bad, my mistake. Taking Jonathon advice, I measured out 1.6 meters at 105mm - which is the nearest point on my SLR and focused to that on the chart (which works great). It now looks better and seems to focus alright. I won't be able to really tell until the MACRO filter that I ordered comes in - called today and still not there! Right now I am trying something new. I have tried the Tracing Paper route - and mine is too thick. Nice picture from the GG, but too dark. I need a light grade or gauge. Still looking - but what I did was this : I sprayed the CD with Spray glue and then looked at it - my goodness, doesn't it look like a frosted CD with just the glue on it? Going to run some test when it dries to see if this is another viable option. Mark, good on you! Keep me posted on your progress.