Fresnel screens/brighter ground glass?

[Dave Dawson]

I find the Sinar gg/fresnel to be dissapointing compared with other combinations. Because there are two focusing planes when the fresnel is fitted it makes focusing impossible and you have to focus without the fresnel and compose with. This is due to the fact that the ridges of the fresnel is mounted behind the gg and is in contact with the smooth side of the gg which means there is about 1.5mm space between them.

In other systems I've used in the past, the fresnel is mounted on the lens side of the gg with the ridges in contact with the rough side of the gg so there is only one focusing plane, so focusing can be done easily with the fresnel permenantly in place.

It's also a pain storing the fresnel when off the camera resulting in it getting lost or scratched.

Just my two cents worth!

Cheers Dave

[Arne Croell]

I find the Sinar gg/fresnel to be dissapointing compared with other combinations. Because there are two focusing planes when the fresnel is fitted it makes focusing impossible and you have to focus without the fresnel and compose with. This is due to the fact that the ridges of the fresnel is mounted behind the gg and is in contact with the smooth side of the gg which means there is about 1.5mm space between them.

In other systems I've used in the past, the fresnel is mounted on the lens side of the gg with the ridges in contact with the rough side of the gg so there is only one focusing plane, so focusing can be done easily with the fresnel permenantly in place.

It's also a pain storing the fresnel when off the camera resulting in it getting lost or scratched.

Just my two cents worth!

Cheers Dave

Actually it has to be permanently in place. As discussed in several other threads before (like the Chamonix problem one), the downside is that the fresnel changes the optical path and that has to be corrected by shifting the ground glass position. If one takes the fresnel out, the focus plane of the ground glass and the film plane are no longer the same.

[Dave Dawson]

Actually it has to be permanently in place. As discussed in several other threads before (like the Chamonix problem one), the downside is that the fresnel changes the optical path and that has to be corrected by shifting the ground glass position. If one takes the fresnel out, the focus plane of the ground glass and the film plane are no longer the same.

That makes no sense atall...........You can ONLY focus on the ground glass. If you focus on the fresnel it will not be in the same place as the film I'll leave it there for now.

Cheers Dave

[Frank Petronio]

What Arne said. It's that way with all cameras using fresnels on the lens side of the ground glass.

I don't care for fresnels, I rather see the image without ridges and such. Try to let your eyes adjust....

[Steve Hamley]

That makes no sense at all...........
Cheers Dave

It makes perfect sense. A fresnel lens is a lens, and when it's in front of the GG it's in the path of image-forming light, but it isn't when the film holder is in place.

So try an experiment with any other lens; tape a weak magnifying glass or spectacle lens behind the taking lens, focus (if you can), then remove the magnifying glass. Would you expect the image to still be in focus? The only difference is that the magnifying glass is behind the lens instead of in front of the GG.

But it's incredibly apparent from the Chamonix threads that people don't understand that lenses affect focus. Maybe because fresnels don't look like a regular lens.

Cheers, Steve

[Dave Dawson]

Steve....Is my posting #11 rubbish then?

Cheers Dave

[Dave Dawson]

I geuss not the ?

Cheers Dave