$10 Fresnel for 8x10

[ic-racer]

On the way home from work the other day I stopped at Staples and picked up that fresnel lens for about $10. http://www.staples.com/Staples-Full-Page-Magnifier/product_931974?cm_mmc=GoogleBase-_-Shopping-_-Furniture%3EMaps_Magnifiers_%26_Flags-_-931974-10644-CC

It is made of that brittle plastic that is a little difficult to cut cleanly. I got a few cracks, but I just wanted to saw it up quickly to see if it made much of a difference with my 210mm and 125mm lenses.

Wow, I'm sold on a fresnel now, I can't believe I have been struggling to see the edges all this time.

I'm not sure at this point if I'll just keep this one (the cracks don't bother me) or get another one just like it and do a good job trimming it, or cough up some cash for a fresnel made for 8x10 photography. The lens pattern on the Staples lens is coarser than the pattern on my Horseman brand 4x5 and 6x9cm fresnels.

[Caivman]

Walmart sells these too in the toy department. They're mounted in a sort of handle/frame deal and can be cut reasonably with scissors.

Anybody looking for a cheap Fresnel might be in luck with one of these.
Think it was 8$ if my memory serves me correctly.

http://www.walmart.com/ip/Super-Wide-View-Mega-Magnifier/13441585

found the link, looks like i might have found mine on clearance for 40-50% off.

[Robert Hughes]

I picked up an 8x10 fresnel from Office Max last November for my homemade box camera, it works just fine, and my focus point is dead-on. :)

[Caivman]

only thing i hate is how flimzy these things are. I thought about marine-epoxy attachment to a 1/8" sheet of glazing to keep it rigid, but can't see a great way of pulling this off without screwing up the fact that it's freznel.

[Marek Warunkiewicz]

Hi all!

How did you attach it to the ground glass? Can you post some pix?

Thanks!

Marek

[ic-racer]

Hi all!

How did you attach it to the ground glass? Can you post some pix?

Thanks!

Marek

Actually the "Staples" one is about one eight of an inch thick and actually acts like a ground glass protector.

My Shen-Hao has two finger-like metal pieces that bend down to hold the recessed ground glass. I ground out notches in the fresnel, so the metal fingers still touch the ground glass, but now two areas of the fresnel now slip under the metal finger piece wich holds the fresnel in place without any modification to the camera.

I guess I need a picture to show that.

[Caivman]

Didn't think about the fact that there's a little flange holding my GG in place... Might work if i just slide it behind that.

The one from walmart is only about 1/16th (plus a bit) thick, so it might just slide between the glass and the holder. Good call.

Marek, i was planning on using a Ultraviolet Curing epoxy (glass clear) to seal my thin sheet of freznel onto my glass, but seeing the above post, i'm going to try something a little less permanant first.

[ic-racer]

Just some pictures of how the fresnel is held to the back of the camera with absolutely no modification to the camera. I ground out a tab on the fresnel that slips under the finger ground glass holder.

[Wally]

I tried this with one I found at Staples about 3 years ago, on an old Calumet C400.

Here's what I remember:

It was easy to cut with a _good_ pair of sharp scissors.

The correct side to locate the fresnel is between the GG and the lensboard, with it's grooves facing the GG.

The problem with just putting it in first before the GG is that the focus plane is not in the same place as without it, so your images will not be as sharp as you saw on the GG.

The right thing to do is to mill out a space the depth of the fresnel so the GG is where it was. Or something very close to it. Search the forum on this topic and you'll find some good technical info.

I bought a fresnel for my Shen Hao and found that they had a little recessed area for it to nestle into so that the GG was where it had been, not moved back toward me by the thickness of the fresnel.

[Drew Bedo]

The fresnel is mounted on what side of the GG . . .I assume on the side away from the lens?

[Kevin Crisp]

Drew: Typically, the ground glass stays where it has always been, the Fresnel is behind it (closer to the photographer) with the fine grooves up against the ground glass and the smooth side of the Fresnel facing the photographer. There are some cameras such as the Graphics, which placed the Fresnel in front of the ground glass. I doubt one of these cheapies would work with a Graphic that had somehow lost its original Kodak Fresnel.

My Canham 4X10 had just a ground glass, I added one of these really thin reading Fresnels and the image is much more even and easy to see. The one I have bulges a little on the 10" dimention, but is fine when the loupe is against it to focus.

[ic-racer]

Shen Hao does not sell a fresnel for the 8x10 and they have no groove provision for mounting one in front of the GG.

This screen is a quarter of an inch thick. Mounting it behind the ground glass offers GG protection and the possibility of an installation without any camera modification.

Of about 12 cameras with focus screens I own, 3 have the fresnel behind the GG and the other 9 have it between the lens and GG. The lines of the fresnel are less pronounced when mounted between the lens and GG, but they work just fine when in the other position.

[Wally]

No, it actually goes on the side between the lens and the GG. But to correctly place it, it should not move the GG with respect to the film plane, so a shallow bit of material must be removed from the area that the GG sits in so that when the GG goes back in, it sits where it did before.

If you don't do this, then the GG will be at a different place than the film in the film holder with respect to the lens.

Sometimes you can get away with this if you (a) shoot landscapes (and therefore stop down quite a bit) and (b) you don't need too small a circle of confusion (ie, you're not going to enlarge the image much beyond 2x). In these circumstances you might not notice any loss of apparent sharpness.

But if you shoot portraits, and you focus on the eyes, and don't stop down much, you'll often find that the eyes are a bit soft and the chin whiskers are extremely sharp.

[JoeV]

For my 8x10 box camera project I ended up using the Staples brand Fresnel lens as the ground glass. One side is Fresnel, the other side is blank. I ground the blank side down with a random orbital sander and 320 grit emory into a usable ground glass-like surface, which is oriented in the camera facing the lens. It offers a nice, bright image. The only caveat is the flexibility of the plastic means that for critical focus you don't want to push on the plastic with your loupe, else you'll effect focus accuracy.

~Joe

[Wally]

Shen Hao does not sell a fresnel for the 8x10 and they have no groove provision for mounting one in front of the GG.

This screen is a quarter of an inch thick. Mounting it behind the ground glass offers GG protection and the possibility of an installation without any camera modification.

Of about 12 cameras with focus screens I own, 3 have the fresnel behind the GG and the other 9 have it between the lens and GG. The lines of the fresnel are less pronounced when mounted between the lens and GG, but they work just fine when in the other position.

Do you mount it with the grooves facing toward or away from the ground glass?

I don't have the Shen Hao 8x10, just the lowly 4x5.

In that model, the fresnel gets mounted between the GG and the lens, in it's own little recessed space.

I'm no optics person, just a duffer with a camera, so I defer to the members that described the correct placement of a fresnel in older posts on this site. They said that any mod that changes where the ground glass is must be carefully done as it changes the actual focus point, so one must be careful to place it such that it renders on the ground glass at the same plane as the film when you put the holder in, which (IIRC) is .187 inches from the film holder flange. This measured distance is only valid for a ground glass that does not have a fresnel - if one is added to the optical path, the actual focus point can shift. By how much I don't remember. I assume it's something to do with the fact that the fresnel is bending the light.

It should be an easy enough thing to check for, of course. Just take a pic of a ruler that's at a 15 degree offset from being parallel to the plane of sharp focus, then focus carefully at the 6 inch mark, expose with a fairly wide aperture to accentuate the in-focus area, and develop. See if the six-inch mark is where the film found the smallest circles of confusion.

As for the idea that putting it on the outside, between the photographer and the ground glass was wrong, I may have read that here or been told by my mentor here in San Diego. I can't recall right now, and I'm too sleepy to search the archives tonight.

[IanG]

No, it actually goes on the side between the lens and the GG. But to correctly place it, it should not move the GG with respect to the film plane, so a shallow bit of material must be removed from the area that the GG sits in so that when the GG goes back in, it sits where it did before.

There's no correct place. Some manufacturers use a fresnel behind the screen others in front.

The best is the super screen combination the all in one fresnel and ground glass, Beattie Intenscreen, Maxwell etc, although some manufacturers like Wista, Linhof offer similar screens although there's slight variations in brightness etc, and more importantly cost

I did some tests last years with two 5x4 camera's, and with a good ground glass screen & a fresnel brightness improved significantly over a plain glass screen but didn't quite reach the standard of my Wista combination screen.

Like ic-racer I bought some of the Staples type fresnels and I'm using one for my second 10x8 Agfa Ansco, the first came with a new, boxed Beattie screen :D

Ian

[Wally]

There's no correct place. Some manufacturers use a fresnel behind the screen others in front.

The best is the super screen combination the all in one fresnel and ground glass, Beattie Intenscreen, Maxwell etc, although some manufacturers like Wista, Linhof offer similar screens although there's slight variations in brightness etc, and more importantly cost

I did some tests last years with two 5x4 camera's, and with a good ground glass screen & a fresnel brightness improved significantly over a plain glass screen but didn't quite reach the standard of my Wista combination screen.

Like ic-racer I bought some of the Staples type fresnels and I'm using one for my second 10x8 Agfa Ansco, the first came with a new, boxed Beattie screen :D

Ian

Thanks for the update. I stand corrected.


// Wally