Fresnel lens

[seawolf66]

Does a Fresnel lens really improve focusing for you?

[rdenney]

No, that's not its purpose. A Fresnel gather light and points it back to your eye, so that you can see the whole image from edge to edge with enough brightness to compose the photograph. If anything, most Fresnels make focusing using a loupe more difficult, because the Fresnel pattern is a distraction when magnified. Many camera manufacturers made the Fresnel easily removable for focusing, e.g. Sinar.

With short, slow lenses, one might require a Fresnel to see enough of the image to even be able to see the edges, but then the Fresnel has to be designed for such short lenses to be completely effective. Lenses much too short for the Fresnel will cause ghosting and other artifacts in the Fresnel that actually undermine its use.

Rick "noting the Fresnels that one can focus through easily are expensive" Denney

[BrianShaw]

When using a loupe, no.

When not using a loupe, yes.

[IanG]

Yes a fresnel lens in combination with a good ground glass screen can help enormously with focussing by increasing the brightness substantially.

About 4 yeras ago I realised that my Crown Graphic was substantially harder to focus than my Wista putting the two side by side there was over 3 stops difference in overall brightness despite the fact that the Crown had an f4.5 lens and the Wista f5.6 (both 150mm at full aperture). The Wista has a combination screen'fresnel.

I measured the differences in brightness (using a Spotmeter) and also stopped the Wista's lens down until they matched in brightness (the differences matched) and it was 3 and 1/3 stops, admiottedly the Crown had it's original screen.

Changing the Crown's screen for a Steve Hopf one increased brightness by about a stop, adding a fresnel took it closer to the Wista's combination screen/fresnel and about 2½ stops brighter than it had been. That improvement means it's new very much easier to focus particularly when used hand held, the focus hood is fine on it's own.

Since then I've fitted new screens to all my other LF cameras, it made the a big difference to my German pre-WWII 9x12 cameras (Orion Werks, Rodenstock, KW Patent Etui's etc) these can now be focussed easily even in quite low light. If I could find the right fresnels I'd fit then as well).

Ian

[TheDeardorffGuy]

Fresnel lens..........I hate them. Really truely hate them. You really need different ones for different FL lenses. A really nice fine grind ground glass with the corners cut works just fine. In 40 years of doing this I've seen so many Fresnel lens come and go on the market.....If there was one perfect one it would still be there and this question would not be asked. (I do not blame you at asking it at all, It needs to be asked!!)

[seawolf66]

Basically my eye's are getting older , Just was wondering if the Fresnel lens would help me out in focusing I use a lope but some
times it a hit or miss with me for being on the money with sharpness : thanks all you folks for your answers
below are two just in last few day as you see one is good the is close but no cigar.

[TheDeardorffGuy]

You need a loupe that is adjustable to your eyes. The other day I found all my Agfa style loupes that I modified to focus for my eyes. I machine a bit off the bottom edge. Now I need to add a bit!! I finally got a Schneider loupe and love it. I drew a + on the GG and focus on it. Thats it.

[Bob Salomon]

I hope you are drawing that + on the grain side of the gg and not the non-imaging forming side of the gg.

[IanG]

]Basically my eye's are getting older , Just was wondering if the Fresnel lens would help me out in focusing I use a lope but some
times it a hit or miss with me for being on the money with sharpness : thanks all you folks for your answers
below are two just in last few day as you see one is good the is close but no cigar.

You need to try one and see. There is some variation in fresnels and some people swear by the more expensive Maxwell or Beattie screens.

While I can see where Ken's coming from not liking Fresnels there's a good reasons for using them as well which is why many cameras are sold with them fitted. Many of us find they make focussing very much easier and I very rarely need to use a loupe.

Ian

[E. von Hoegh]

Does a Fresnel lens really improve focusing for you?

No.