Fresnel on sinar

[bill spears]

Hi everyone,
Just a straightforward dumb question which I guess has been answered a thousand times. [Tried to do a search for this one but can never seem to find what I need].
Have just aquired a fresnel screen for my Sinar F in the hope it will brighten up the groundglass when using a 65mm SA but not sure which way it fits !

Outside or inside the groundglass ??
With the rings against the glass or not ??

Cheers
Bill

 

[GeorgesGiralt]

Hi !
If I look at the original Fresnel for my Norma, it is enclosed in a frame with protruding pins. So it can only go one way : between the photographer's eye and the ground glass. I do not think the way it touches the GG is relevant, but mine has the grooves touching the GG.
Hope this helps.

 

[Don Dudenbostel]

George - I had the same Fresnel when i bought my Norma in 69 but changed it to the inner lens. The inner lens had to be made to fit so that the GG is spaced a certain distance from it's normal focal point to compensate for the Fresnel. Actually the Fresnel is beveled to fit a certain distance into the inner frame. Just placing a Fresnel in the light path won't work. It will throw the focus off. My inner Fresnel is placed so the rings touch the GG. Bill for your needs the outer position will work without focus correction I believe.

 

[Struan Gray]

The older Norma Fresnels were designed to go between the ground glass and the lens. You have to remove the ground glass from its frame and install the Fresnel under it - there were tabs at the side to move the ground glass back by the correct distance to compensate for the focus shift introduced by the Fresnel.

Later Fresnels, including all those with frames round them, were designed to go on the outside of the camera, between the ground glass and your eyes.

The first method protects the Fresnel. The second allows you to remove it easily for fine focussing or if it vignettes a wide angle lens too much.

 

[edtbjon]

You attach (snap) the fresnel frame in between you and the groundglass. I've taken some pics so that everything hopefully becomes clear.

//Björn

 

[Paul.]

Bjorn,
I have the frenzel frame but no screen on my camera, would you know if the screens are available seperatly please?
Regards Paul.

 

[bill spears]

I think my fresnel is not a genuine Sinar part, just a plastic screen I bought online. Its also a bit smaller than the groundglass. I've had to do a small bodge and held it in place under the retaining tabs that hold the groundglass in. Seems to be working OK.
One problem I am encountering is my loupe magnifying the circular lines too much. This is probably because its a 7x which is too powerful ??

Seems like these screens are not too abundant on the secondhand market, and sometimes fetch high prices.
I've never seen any genuine Sinar ones.
Thanks for your replies.
Bill

 

[edtbjon]

Paul, as far as I know, the 4X5" fresnels are only available with the frame. They are a bit expensive, but they makes life (eh, viewing) easier most of the time.

Bill. Yes of course you can do with whatever solution that works. The original just seem to work that little bit better. I normally use the Sinar magnifiers, which are found on either a simple plate which is used with an intermediate bellows or, when at home, a mirror housing. These magnifiers are more like 3-4 diopter reading glasses.

Which is another tip. I.e. strong reading glasses instead of expensive loupes. The negative side of these is the "strange monologue" that can happen:
"Now where did I put those glasses??? "
(after 5 minutes...)
"Ah, on my forehead. But why did I need them???"

//Björn

 

[Struan Gray]

My original Sinar Fresnel is on my 5x7 conversion. For 4x5 I use a "Midi Sheet Magnifier" from these people:

http://www.magnifyingglasses.co.uk/acatalog/Online_Catalogue_Page___Sheet_Magnifiers_8.html

wedges nicely into place in a Norma back, or can be held in with blu-tak if it's extra windy (or I'm looking up).

MXV is good UK source of Sinar bits and pieces at reasonable prices. Otherwise, the German eBay, eBay.de, is a treasure trove - framed Sinar Fresnels turn up there very often.

You won't ever get rid of the Fresnel lines. The OEM Fresnels are better than cheap magnifiers, but they are behind the gg and mounted in frames precisely so that they can be easily removed for fine-focussing.