Crown Graphic Fresnel?

davidave · Jun 29, 2010

Is there a way to tell if the fresnel is installed on a Crown Graphic just by looking through the ground glass? Through my research I've discovered the fresnel is a necessary focusing element, but I want to make sure *bay auctions include the fresnel.

Bertil · Jun 29, 2010

Shouldn't be any problem: open up the lens (or take it away) use a loupe and you should see the fresnel rings - if they are there!
/Bertil

Ian Grant · Jun 29, 2010

Not all Pacemaker Speed & Crown Graphics came with a fresnel. The difference in overall screen brightness is quite noticeable when a fresnel's present.

The back frame for the original screen/fresnel combination has a different register to the plain screen version because the fresnel is lens side of the screen. You can fit a fresnel to the rear on the plain screen Graphics.

Few sellers mention whether there's a fresnel.

Ian

davidave · Jun 30, 2010

Thanks for the replies guys. I stumbled upon another test where the guy measured the ground glass to film plane distance. He said there was about a 1mm difference and calibrated the rangefinder to compensate. He then did focus test and everything came out perfect. The conclusion was that there should have been a fresnel (about 1mm thick) in place. Makes sense!

Ian Grant · Jun 30, 2010

He should have shimmed the screen, which is very simple, because the screen is still out of tolerance so not accurate. So as soon a s any movements are used the range-finder is useless and the screen as well

Ian

Wade D · Jul 1, 2010

The fresnel is nice to have but not a necessity. My old Speed Graphic Anni doesn't have one and it focuses just fine. The rangefinder is spot on as well.

Ian Grant · Jul 1, 2010

Wade D said:
The fresnel is nice to have but not a necessity. My old Speed Graphic Anni doesn't have one and it focuses just fine. The rangefinder is spot on as well.

A fresnel does make a huge difference to overall screen brightness though, over 2 stops when measured with a spot-meter.

Ian

Fotoguy20d · Jul 1, 2010

Bertil said:
Shouldn't be any problem: open up the lens (or take it away) use a loupe and you should see the fresnel rings - if they are there!
/Bertil

You won't need a loupe. The fresnel is very noticeable on the inside - light reflecting off it makes a distinctive pattern. Also, you can feel it.

Dan

Wade D · Jul 2, 2010

Ian Grant said:
A fresnel does make a huge difference to overall screen brightness though, over 2 stops when measured with a spot-meter.

Ian

I agree that the fresnel makes focusing much easier but to a practiced eye the standard ground glass works well enough. At least for me. I am planning on re-grinding the old screen using your great instructions. Never thought it would be so simple!

Crown Graphic Fresnel?

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