View previous topic :: View next topic |
Author |
Message |
Mark_Davies
Joined: 11 Aug 2005 Posts: 23 Location: Australia
|
Posted: Mon Oct 24, 2005 7:05 am Post subject: |
|
|
Hi Folk, I would like confirmation of measuring GG distance. I have a new fresnel and wish to confirm the distance of the GG is going to be correct for my camera. What I am doing is putting in a DD and measuring from the front of a lens panel to the surface of the DD that has dd slide removed and a film inserted in the DD holder. Then I measure the distance of the front of the lens panel to the fresnel. Add thickness of fresnel as GG is on outside of fresnel (further away from lens panel). The two should be the same. If it is not, then add ship to pack out GG to same distance as DD with film distance. Could someone please confirm this is correct?
Thanks,
Mark |
|
Back to top |
|
 |
Mark_Davies
Joined: 11 Aug 2005 Posts: 23 Location: Australia
|
Posted: Mon Oct 24, 2005 1:47 pm Post subject: |
|
|
I should have said it is on the Super Speed, and that not to add "ship" to pack out but to add "shim" to pack out.
The reason for this request is that I have purchased a toyo GG to replace the older one, and the toyo is bigger and sits on a metal molding. I believe I have to cut the GG so it sits on the fresnel, but the new fresnel is thinner than the older one. Hence the need to check what I am doing is correct.
Thanks,
Mark |
|
Back to top |
|
 |
RichS
Joined: 18 Oct 2001 Posts: 1468 Location: South of Rochester, NY
|
Posted: Mon Oct 24, 2005 3:42 pm Post subject: |
|
|
I have no idea why you're doing the replacement, unless the old one was broken or scratched terribly?
If you search the forums for GG and ektalite, you'll find a few discussions on placement and other suggestions.
In this case, I think you can only get close unless you do actual focussing measurements. It has been said that the freznel changes the focal point of the GG. So a different freznel will technically produce a different spacing for the GG placement.
I used to know the distance from the film plane to the back surface (.195 comes to mind, but I can't find it)... Measuring from the lens board will not be accurate. I would remove the back, place a non-flexing bar across the surface of the back and measure from the bar to the film plane. Subtract the thickness of the bar. Way back when, I did checks on holder flatness this way and checked various Graflok focus panals.
It might work to either use the GG and frexnels simply sandwiched together in the same position as the original? It might also work to shim it out so the ground surface is in the same position as the old one? With the different freznel, I wouldn't know and you'll probably get conflicting opinions.
If you need any measurements off another Super let me know. If you need that exact measurement from the back plane to the film plane, let me know and I'll try to find it. I know it was posted in the forums a few times... And if you want to get rid of your old GG/Ektalite, let me know
Good luck!
|
|
Back to top |
|
 |
Mark_Davies
Joined: 11 Aug 2005 Posts: 23 Location: Australia
|
Posted: Tue Oct 25, 2005 12:02 am Post subject: |
|
|
Thanks Rich. I did take a look at the history but did not see anything about where the GG sits within the back. It does describe sequence of smooth fresnel surface/ribbed fresnel surface to etched GG side/smooth GG side to eyes. I have the Crown and the Super and the two fresnels are different as are the two GG's. How do I tell which is the ecktalite? As the cameras are both 40 odd years old, could they not both have been replaced with different ones from the original?
I am replacing them to try to get a brighter focusing screen. I used to have an ebony and that was so much brighter than these. Neither of these have grid lines and I also like to see these for allignment of horizons and building walls.
You say "remove the back, place a non-flexing bar across the surface of the back and measure from the bar to the film plane. Subtract the thickness of the bar."
When I remove the back how do you measure from the back to the film plane? If I put a bar across the back which is now removed, the film plane cannot be attached to the back. If I measure from the back which is on the body of the camera, I have to measure the distance from the lens panel to the film plane, which is within a film holder, which needs to be attached to the camera. I don't intend to be thick but I don't understand. Sorry, and thanks for your help. You are welcome to the old GG and fresnel if I can get these new ones working. All you have to do is pay for the freight. I am in Australia.
Regards,,
Mark |
|
Back to top |
|
 |
Dan Fromm
Joined: 14 May 2001 Posts: 2148 Location: New Jersey
|
Posted: Tue Oct 25, 2005 12:46 am Post subject: |
|
|
Quote: |
On 2005-10-24 17:02, Mark_Davies wrote:
Thanks Rich. I did take a look at the history but did not see anything about where the GG sits within the back. It does describe sequence of smooth fresnel surface/ribbed fresnel surface to etched GG side/smooth GG side to eyes. I have the Crown and the Super and the two fresnels are different as are the two GG's. How do I tell which is the ecktalite? As the cameras are both 40 odd years old, could they not both have been replaced with different ones from the original?
I am replacing them to try to get a brighter focusing screen. I used to have an ebony and that was so much brighter than these. Neither of these have grid lines and I also like to see these for allignment of horizons and building walls.
Regards,,
Mark
| Mark, excuse my slowness. So you have a Crown and a Speed, each with a fresnel in the focusing panel. And each has it in the right place, i.e., on the lens side of the GG, ridges up against the ground side of the GG.
If that's your situation and you can now focus accurately on both GGs, have you considered washing the GGs and fresnels? Washing works wonders. And you can replace the GGs with nice ones. SatinSnow brand is highly recommended, although the company has a massive backlog and is very slow to fill new orders.
FWIW, there's just one focusing panel casting for each size of Pacemaker Graphic. And AFAIK there's just one casting number per size. The difference between a focusing panel made to be used with a fresnel and one made to be used without is that the one for a fresnel has the bosses on which the GG sits milled down to adjust for the fresnel's thickness. So, next question, are your two focusing panels identical? Are your two fresnels the same thickness at the edges? Go measure and tell us what you find.
Good luck, have fun, please report back, and whatever you do, don't panic,
Dan |
|
Back to top |
|
 |
45PSS
Joined: 28 Sep 2001 Posts: 4081 Location: Mid Peninsula, Ca.
|
Posted: Tue Oct 25, 2005 2:25 am Post subject: |
|
|
[ This Message was edited by: 45PSS on 2005-12-24 21:11 ] |
|
Back to top |
|
 |
Mark_Davies
Joined: 11 Aug 2005 Posts: 23 Location: Australia
|
Posted: Tue Oct 25, 2005 2:57 am Post subject: |
|
|
Hi Dan, I hope this is not too long. I am only trying to get the Super Speed better as that has the extra movements I am looking for. Yes, ribs of the fresnel sandwiched in the middle of the fresnel and GG.
The moulding number of the back is 36074. The GG on it is 1.50mm (0.061")thick and 122mm x 100.1mm (4.786" x 3.964"). The fresnel is the same width and length but is 1.9mm (0.074")thick. I have looked and enquired from Satin Snow but they do not have grid lines or the 6x7 and 6x9 frame lines. The toyo does. My new fresnel is only 1.2mm (0.045") thick a difference of 0.7mm (0.029"). The total difference between the older fresnel/GG combination to front of panel v's film surface to front of lens panel for a given position of the lens is 0.45mm. The difference between my new fresnel/GG combination to front of panel v's film surface to front of lens panel os 0.05mm. This is possibly why this camera was sold: the focus point on the GG was .45mm away from where the film surface was: thereby making a sharp focus possible.
So, Back to my original thought. If I place a lens, say a 150mm lens, on the camera on a lensboard, focus the image on the GG. Remove lens but LEAVE the lens panel mounted. Measure from front of lens panel to Fresnel. Add thickness of fresnel. I should then have the distance from front of lens panel to the surface of GG. This should be the same for front of panel to film surface when there is film in the DD and the DD is on camera. As the film is the item on which we want the actual and correctly focused image, this must be the distance to which we place the image side of the GG. Is this correct? If so, then the previous fresnel was holding the GG further away from the film plane than my new ebony fresnel by 0.04mm.
Hence, if my above assumptions are correct, I should only have to pack out the GG by 0.05mm (almost negligable) and it should be perfect.
Any thoughts would be appreciated.
Again, many thanks,
Mark |
|
Back to top |
|
 |
RichS
Joined: 18 Oct 2001 Posts: 1468 Location: South of Rochester, NY
|
Posted: Tue Oct 25, 2005 2:59 am Post subject: |
|
|
Mark,
Do NOT remove the entire back from your camera (unless you want to). All you have to do is slide off the focus panel.
On the Super panel: The inside of the panel (that normally faces the lens) has four raised areas on the corners. This is where you measure to the freznel/GG. You can go from one corner to the other, either along a side or across a diagonal.
A quick measurment here goves approx. .145" from the back plane to the Ektalite.
You may be right about the Ektalites being different between the Pacemakers and Supers, but I hadn't noticed? I even placed a Pacemaker Ektalite into my Super because it was missing it when I bought it. Haven't seen a problem with it and back then, the measurements did add up for me. I wish I could remember where those exact measurements are??? I know it's in one of these books around here someplace...
|
|
Back to top |
|
 |
RichS
Joined: 18 Oct 2001 Posts: 1468 Location: South of Rochester, NY
|
Posted: Tue Oct 25, 2005 3:15 am Post subject: |
|
|
Ah, knew I had it. The PAcemaker Speed & Crown manual...
The exact measurement from back plane to Ektalite is .139" +-0.002".
This will be the same for any Graflok back as all film holders are manufactured for this distance from back plane to film plane, so it holds also for the Super...
_________________ ----------------------------------------
"Ya just can't have too many GVIIs"
---------------------------------------- |
|
Back to top |
|
 |
Mark_Davies
Joined: 11 Aug 2005 Posts: 23 Location: Australia
|
Posted: Tue Oct 25, 2005 3:26 am Post subject: |
|
|
Hi 45PSS,
Thanks, I have done all up to step 4 and am ready for placing parallel level etc. If I had seen this before my post I could have saved some typing. I can now clean camera a bit from the ages of dirt accumulation. One point I would appreciate if you could clarify.
You say "Optical point of ektalite screen/ground glass combo should be at the same distance. Ground glass only will be the same distance. Try ground glass at distance plus 1/2 the thickness of the fresnel."
Could you explain this again please? I don't quite get the gist of it.
Thanks,
Mark |
|
Back to top |
|
 |
Mark_Davies
Joined: 11 Aug 2005 Posts: 23 Location: Australia
|
Posted: Tue Oct 25, 2005 4:12 am Post subject: |
|
|
Hi Rich, I had it off before I noticed your post.
Hi 45PSS, What I am not getting is to measure from the bar across the back down to the fresnel, I must then add the thickness of the fresnel to get the correct distance to the GG focusing side, hence, to the film plane. Is this correct?
If so, then my fresnel gets a closer total distance from bar to GG than the older ones as the older fresnel is thicker. Readings I have are:
Old fresnel: 0.074" thick
New Fresnel: 0.045" thick
Distance from: bar to film surface: 1.126"
Distance from: bar to lens side of fresnel (LSOF):1.083"
Sums:
Bar to LSOF + Thickness of Old Fresnel:1.157"
Bar to LSOF + Thickness of new Fresnel:1.128"
This means the distance to the GG with my new fresnel in is closer to the Bar-Film distance by 0.029".
Hence, I believe I can just put it in as planned, do your test for confirmation, and hopefully it will prove correct.
How does this sound?
Regards,
Mark |
|
Back to top |
|
 |
45PSS
Joined: 28 Sep 2001 Posts: 4081 Location: Mid Peninsula, Ca.
|
Posted: Tue Oct 25, 2005 5:41 am Post subject: |
|
|
[ This Message was edited by: 45PSS on 2005-12-24 21:11 ] |
|
Back to top |
|
 |
Mark_Davies
Joined: 11 Aug 2005 Posts: 23 Location: Australia
|
Posted: Sun Oct 30, 2005 10:28 am Post subject: |
|
|
Gents, I have done what was suggested: put take measure out and took photo from 2feet with 135mm lens @ f5.6 at 45 deg angle and developed film. fantastic: all okay and crips. Maybe a touch out toward further distance being in focus, possibly instead of the 1000mm being in sharp focus, it would be about 1003mm in sharp focus. But that as stated, is @ 2 feet @ f5.6 with 4x5 neg in slide projector looking at image 15feet away on screen.
RichS. If you want the removed fresnel and GG, they are yours. If you want to send me an email of your address, I will post them to you.
Thanks to all for your help. It is greatly appreciated. I now have an ebony fresnel and a Toyo GG with grid lines and 6x7 + 6x9 framelines, and it is nice and bright.
Many thanks again.
Mark |
|
Back to top |
|
 |
45PSS
Joined: 28 Sep 2001 Posts: 4081 Location: Mid Peninsula, Ca.
|
Posted: Mon Oct 31, 2005 6:09 am Post subject: |
|
|
[ This Message was edited by: 45PSS on 2005-12-24 21:12 ] |
|
Back to top |
|
 |
Mark_Davies
Joined: 11 Aug 2005 Posts: 23 Location: Australia
|
Posted: Tue Nov 01, 2005 12:41 am Post subject: |
|
|
Hi 45PS, I forgot the old "is the slide projector square to the screen trick." I will get out a loupe.
Thanks,
Mark |
|
Back to top |
|
 |
|
|
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|