Hello, I just bought a Shen Hao 5x4 camera. I was wondering what others opinions on focusing screens were. I have heard that the Fresnel is much better for looking through, as it allows much more light in, and produces a sharper image. On the other hand I have also heard that it is more prone to flare, as there is no ground glass to diffuse the light. Does anybody have any preference?
Thanks
I've never heard or read about a fresnel being used instead of ground glass; usually they are used together.
Yes, adding a fresnel may increase brightness but I don't think they ever produce a sharper image. They often are more difficult to focus with using a loupe. I only use a fresnel when it was part of the original design - specifically, the Graflex system - and have never been happy when fresnel is an add-on. Even with a f/8 lens I find the ground glass brightness to be bright enough for proper focusing.
I prefer not using a fresnel for the reasons outlined above by Brian; I just use the best GG I can afford.
Some makers, like Wista and Tachihara, incorporate the GG and fresnel into one piece of acrylic, and these have been very satisfying to use.
I bought a fresnel for my Cambo 4x5 off eBay from a guy in China who custom makes fresnels. The one I received didn't come with a ground glass, just a fresnel and a sheet of clear, protective glass (I assume to stop the fresnel from scratching more than anything).Originally Posted by BrianShaw
It does work and is very bright but using a loupe on it, you can really see the lines of the fresnel. It may well be the fresnel has been "ground" but doesn't really look like it.
If it does not look like it, it probably is not (if you bought it as a fresnel, and not as a ground glass/fresnel assembly, you'd be expected to attach it to your existing ground glass). A fresnel lens will (seem to) work without ground glass - but you are essentially focusing on a aerial image, which has such a high failure rate on regular photographic subjects that it is not employed on any camera I am aware of, except for process and microscopy gear where the two-dimensional subject and ultra-narrow DOF make it more manageable. Even if you can see the fresnel lines, these have spatial depth, so that they are no useful indicator of the focal plane.
The proper way to use a loupe with a Fresnel is to first focus the loupe (never use a loupe that does not have adjustable diopter adjustment) on thee grain side of the ground glass. Then put the loupe on the smooth side of the Fresnel and focus. Since the grooved side of the Fresnel should be placed against the top (smooth) side of the Gg and the loupe is on the top side (smooth) of the Fresnel the grooves in the Fresnel will not be in focus and should disappear.
A Frsnel will spread the light evenly across the viewing area to eliminate the dark edges and corners that are normal with a GG alone.
Some companies make a sandwiched GG/Fresnel screen - Wista for one, some compaies make a hybred type of Fresnel that has the grooved, Fresnel, surface on one side and a frosted side that works like a ground glass on the other side, the Linhof Super Screen (no longer made) was an example of that type, most companies use a seperate GG and Fresnel.
Welly,
What you have is a GG/fresnel-in-one; the clear glass goes over the GG/fresnel because the latter is rather pliant, and will bend once you put a loupe against it.
I have the same one on a 4x5; it's nice and bright.
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