Graflex.org

Rider · Joined: 13 Jan 2008 Posts: 14

I have an early Pacemaker (1950) with a Graflok back.

I read that with this type of back, if the fresnel lens is removed it could cause focussing issues.

How do I determine if the camera has the original back with fresnel?

C. Henry · Posted: Mon Jan 14, 2008 2:13 am Post subject:

You will have a problem only if the focus panel has been changed from its original configuration. Some Graflok focus panels were made without the fresnel and would be thrown off by improperly adding a fresnel. On the other hand removing the fresnel from a focus panel that was made with one would also introduce a focusing error.
There is an article in Technical Information titled "Field Lens (Fresnel) Placement" that tells how to check the accuracy of the placement of the ground glass. A test shot would only cost one sheet of film.

C. Henry

Rider · Joined: 13 Jan 2008 Posts: 14

I made a couple of exposures, at very close range and near infinity, with the lens wide open.

We'll see how they come out.

troublemaker · Joined: 24 Nov 2003 Posts: 715 Location: So Cal

There are both types, with and without the Ektalite fresnel. If you don't know if you have a fresnel or not, pop the focussing hood off the panel and you should be able to see if there is a fresnel stacked under the ground glass. IF you have it, it might not be a bad idea to remove the retaining screws and take out the glass and fresnel and clean the surfaces with windex and a soft cloth. The proper position for the pieces is with the fresnel in first with the smooth side facing the lens. Then the GG gets set in with the ground side facing the lens on top of the fresnel.
In focussing panels where there was no fresnel, the GG sits on raised step or lip. This lip is along the entire back edge of the opening that the GG and or fresnel sit on along the verticle and horizontal edges of the GG (open at the corners). In those panels where there is intended to be a fresnel, one can see that there is no lip, and on many Graflok focussing panels it is obvious this lip has been milled down before painting to facilitate the proper depth for a fresnel. The fresnel type seems to be much more common with Graflok backs. If your panel was intended for a fresnel and has none, there would need to be proper thickness shims representing the missing fresnel to possitionthe GG at the film plane.
If you still can't determine what you have, or should have, I can post a couple images of the two panels showing the raised lip. I can see it plainly on the panel I have with no fresnel, and also with the ones with, but I know what to look for.

Rider · Joined: 13 Jan 2008 Posts: 14

Yes, pictures would be great! I'll post some of my camera as well.

troublemaker · Joined: 24 Nov 2003 Posts: 715 Location: So Cal

I posted some images for you here:
http://photo.net/photodb/folder?folder_id=672090

You should be able to tell which you without taking anything apart. As I mentioned above, a panel intended for GG and an Ektalite fresnel will have the two panels sandwiched and sitting down flush.

With the GG only panel, the ground glass will be raised up slightly sitting on a raised lip as seen in my images and high lighted with blue.

In the last image, highlighted with orange, the lip has been milled down fluch, or nealry so, to accept the Ektalite screen and keep the GG on the focalplane.

Hope this helps.

Rider · Joined: 13 Jan 2008 Posts: 14

I took the panel out, and I still can't tell if there's a fresnel. It seems to be smooth on both sides, but I sort of see a round pattern that I'm used to seeing on fresnels.

It's rather thick, so could the fresnel actually be taped to the ground glass very tightly?

I'd like to post a picture, but I don't see a way to do it.

troublemaker · Joined: 24 Nov 2003 Posts: 715 Location: So Cal

Are you telling us you removed the four flat head machine screws holding the spring clip retainers over the ground glass, removed the ground glass panel and still can't tell if you have a freznel? Or that you removed the panel hood and could not tell?

On stock factory panels the GG is simply placed over the Fresnel and the spring clips hold them in place. Maybe someone taped the edges but I doubt it. They could be stuck together from years of storage and gunk, but I imagine one could easily see the seam between the two peices in place in the focussing panel as I can on any of mine. The two pieces together are close to an eigth inch thick. I have seen some thick aftermarket ground glass someone tried to use in one of my panels, but I tossed it.

If you haven't taken the GG out of the panel yet, you might as well get a proper fitting screwdriver and do so. If you have a fresnel screen, you'll be wanting to clean between the two as gunk builds up over the years, and then you can tell us exactly what you have there. If you have the glosssy smooth side out facing the lens and also twoards the back of the camera chances are there is a properly fit fresnel. The fine circular lines showing up on your magnifying loupe also suggest this.

45PSS · Posted: Sat Jan 19, 2008 3:43 am Post subject:

Trouble,
Rider has removed the groundglass/fresnel sandwitch and the gg/fres is stuck together.
Rider,
Run some warm water in a pan or sink with some dishwashing soap such as Dawn. Put the GG/fresnel in the water and let it soak for a while. The pieces should seperate. They are not glued or taped together. Once seperated use your finger tips only to wash the surfaces of both the ground glass and fresnel. Do not rub across the ridges of the fresnel, go in the direction that they curve. When finished rince in clean water then add a few drops of Photo Flo to the final rince and rince for 30 seconds to 1 minute then handle by the edges only and and allow them to air/drip dry. I have used Windex also but washing as I have described will work better for older, not been cleaned for years ground glass.
_________________
The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.

Rider · Joined: 13 Jan 2008 Posts: 14

I unscrewed the retainer screws and removed the ground glass panel.

There is a piece of plasticky black tape that goes all around the edge of the ground glass panel. It's either a single piece of glass, or someone has very carefully taped the ground glass and the fresnel together.

troublemaker · Joined: 24 Nov 2003 Posts: 715 Location: So Cal

Very good idea should the two be adhered with gunk.
I've had some musty old closet cameras show up, but haven't had the two pieces require soaking yet.

For the smooth side of the fresnel I use a very fine polish for soft plastics. It removes all fine marks and scratches and if the fresnel ribbed side is in reasonably good condition, I get really nice clear results. I use the same polish for hard plastic lenses like the optical view finders and they come out crystal clear like new.

However, I have a couple focus panels here I have yet to inspect so I think I will try the method described above before polishing thesmooth side and see if I can get the fresnel looking better than the soft cloth as I don't like wiping plastics.
The only really bad fresenel I've had was place backwards in the panel, for who knows how long, and therefore the ribs got some nasty scratches.

45PSS · Posted: Sat Jan 19, 2008 6:38 am Post subject:

Rider,
Someone taped the edges, they do not come from the factory that way.
trouble,
what is the name of the plastic polish?
_________________
The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.

Rider · Joined: 13 Jan 2008 Posts: 14

Here are some pictures. Can you help me identify what I've got?

http://photo.net/photodb/member-photos?user_id=2122521[/url]

45PSS · Posted: Sun Jan 20, 2008 1:46 am Post subject:

The first 3 pictures from left to right are the focus panel complete and picture 4 appears to be a ground glass and fresnel taped together. Look for an end of the tape around the edge and remove the tape to seperate and clean.
_________________
The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.