Silly focusing question (with lupe)

[TJV]

Hi all,
This is a stupid question regarding a problem I'm encountering after switching from my Horseman 45FA to Linhof Technika V. The 45FA has a ground glass and fresnel which I believe, but aren't certain of, is two separate pieces. I have never had a problem focusing when using it. The screen is bright and the grain fine, with the image sharp on the GG. I use a lupe and have always had it set at the "zero" focus position. When using the lupe on the Technika yesterday (the first outing I've had with it) I found it incredibly hard to find a sharp plane of focus. My lupe just didn't seem sharp and I have come to wonder (it's late here so can't test my theory) that this new set up might require a different setting on my lupe to bring the ground glass and not the fresnel into focus? Does this sound plausible? The only explanation to this is that the Linhof fresnel is thicker than that of the Horseman, therefore emphasizing any margin of focus error with the lupe. Does any of this make sense? Am I going crazy?

As an aside, and I'm sure some of you with identify with this, it's funny that when out in the field and encountering these problems, my brain just didn't click to what might have been the cause. I'm so used to one way of doing something that I persevered and pushed on, despite frustrations. I did turn the lupe upside down and wondered why the focused image was so much sharper, but even then I didn't think to adjust the lupe focus for normal viewing, if indeed this was the problem...

T

[Ed Richards]

You just need to calibrate the loupe to the Technika screen, then gaffer tape so it does not drift. If you going to switch between them and screen depths are different, get a second loupe.

[ic-racer]

The only explanation to this is that the Linhof fresnel is thicker than that of the Horseman, therefore emphasizing any margin of focus error with the lupe. Does any of this make sense?
The fresnel pieces are probably the same thickness, but on the Horseman FA the correct position of the fresnel is between the ground glass and the lens. The Linhof may have it either way, but on yours I bet the fresnel is between the ground glass and your loupe.

Just re-adjust you loupe to focus deeper to get the Linhof screen in focus.

[TJV]

Ah, I see. That makes sense, thanks. When I look at the Horseman, the fresnel does indeed seem to be inside the camera. I hadn't noticed this before. I think too my current lupe is too strong, 8x, and I end up with tunnel vision when using it, only seeing a tiny portion of detail and really emphasizing the GG grain and fresnel rings. Last week I ordered a new 4x Lupe that I hope will be easier to use in the field.

I guess it's the little things that make a difference on these cameras, and not all things will affect users in quite the same way. I hadn't really thought about how the Linhof and Horseman would differ in actual use when in the field and perhaps it is what one is used to. At the moment I'm tending to favour the way the Horseman operated. The ratcheted rise on the Linhof might take some getting used to in terms of speed of operation and the Horseman's back had a lot more of a positive seating for the film holder, although this is a small thing to worry about when you're familiar using one or the other. I think I may have fogged three or four sheets yesterday and have learnt my lesson already...

[banjo]

don't blame the lupe AS WE get older we need to change the power of the lupe

[Cor]

Try the Tech V without the Fresnel ?

Best,

Cor

[TJV]

I tried to adjust the lupe today but with no affect on clarity. Think I'll wait until my 4x lupe arrives to see if the lesser magnification makes a difference. Could it be that the Horseman's screen is just finer grained?

[Bob Salomon]

Take the lens off the camera and point the camera at a light source. Now put the loupe on the groundglass and focus the eyepiece until the grain of the ground glass is sharp. Then put the lens back on and try focusing again.

Bear in mind, a V is very old. From the time that your V was made till now Linhof has a much brighter ground glass and a Frensel. You might consider the more recent ones as a replacement for your old ones.

[Doremus Scudder]

FWIW, I now use my loupes reversed almost 100% of the time. Not only does it eliminate the problem you describe when switching camera, but it is a lot easier to get the loupe aligned at the right angle to the "bright spot" when using very short focal length lenses.

Most Fresnel screens are designed for optimum viewing with longer lenses, producing an angle-of-view problem with shorter lenses. Regular ground glass has a similar problem with "bright spots," even though the light is not collimated by a Fresnel.

Placing the loupe base directly on the glass surface gives you a fixed angle of view, i.e., parallel to the glass. This is fairly close to perpendicular to the angle of incidence with long lenses; perpendicular to the angle of incidence being "ideal" for viewing. With shorter lenses, the angle of incidence is much further from perpendicular. Holding the loupe reversed allows one to tilt it to line up the angle of view more perpendicular to the angle of incidence with shorter lenses and results in a much brighter view.

The downside is that one must find the proper distance from the gg manually, since there is nothing now touching the gg. I find this can be done easily by focusing first on the Fresnel pattern or the grid on the gg and then moving very slightly to find the focus for the projected image.

Best,

Doremus Scudder

[TJV]

Bob – I purchased brand new and current Linhof replacement parts so assume they are the modern, more brighter type. Thanks for the tip on finding best lupe settings. I hadn't thought of that way around the problem!


Take the lens off the camera and point the camera at a light source. Now put the loupe on the groundglass and focus the eyepiece until the grain of the ground glass is sharp. Then put the lens back on and try focusing again.

Bear in mind, a V is very old. From the time that your V was made till now Linhof has a much brighter ground glass and a Frensel. You might consider the more recent ones as a replacement for your old ones.

[TJV]

Just tried doing what Bob suggested re. trying to focus on grain with lens off. I can only achieve perfect focus with the lupe reversed. In the normal orientation, I can focus on the fresnel surface but adjusting the lupe from zero only makes things worse. Does this mean that my lupe is faulty?

[TJV]

Just tried doing what Bob suggested re. trying to focus on grain with lens off. I can only achieve perfect focus with the lupe reversed. In the normal orientation, I can focus on the fresnel surface but adjusting the lupe from zero only makes things worse. Does this mean that my lupe is faulty?

I've been thinking (obsessing?) about this and can't understand how I can focus my lupe beyond the immediate surface it rests on. I can't remember using a lupe that allows for focusing as such, only negative diopter adjustments. Am I missing something here? When the diopter is screwed all the way in it seems sharpest, unscrewing it just makes things worse. Sorry for what might be a stupid question but not being able to focus the ground glass like I have been able to with my Horseman (without thinking about it!) is driving me bananas!

[Bob Salomon]

Sounds like your loupe is not adjustable for focus. what loupe do you have?

[TJV]

Thanks for replying, Bob. I'm feeling rather silly asking about this as it seems such a simple thing!

I'm using two models, but only one in the field. I have tried the exercise you suggested with a modern Schneider 3x lupe (designed to view full frame 6x7cm negs,) plus a cheaper Marumi 8x. Last week, purely out of frustration, I ordered a new Rodenstock 4x Lupe and am hoping now that it is actually going to do the job I need it to!


Sounds like your loupe is not adjustable for focus. what loupe do you have?

[E. von Hoegh]

What Bob S. said.

And, it's "loupe".;) They don't work right unless you spell their name correctly.....:D

[Brian Ellis]

I tried to adjust the lupe today but with no affect on clarity. Think I'll wait until my 4x lupe arrives to see if the lesser magnification makes a difference. Could it be that the Horseman's screen is just finer grained?

Yes, it could be. That's what I was thinking when I read your message. There are Fresnels and there are Fresnels. They're lenses and like any lens they aren't all the same. Mine have varied in quality and ease of focusing/use from outstanding (Maxwell) to very good (Deardorf) to pretty good (Tachihara, Beattie, etc.) to poor (Ebony). Although I've owned two Technikas I put a BosScreen on the Tech V and a Maxwell on the Master so I don't think I've ever used a Linhof OE Fresnel, just the plain ground glass (on a Technikardan). But it's certainly possible that the Fresnel on your Horseman was just better quality or was designed to better-suit the lenses you use.

[TJV]

Thanks, Brian. I think on further inspection the problem lies in the fact that my current loupe doesn't allow for focusing past the surface it sits on. It has a diopter adjustment but not a focus as such. Turning the loupe upside down, I'm able to find an extremely sharp image so I don't think it's a GG or fresnel quality issue – I'd hope not considering they're both brand new Linhof parts! I'm scared now that I'll receive the Rodenstock 4x Loupe I ordered and be presented with the same focusing problem.

Ah, I feel really stupid asking these questions, they seem so basic!

[TJV]

Haha, yeah I know. I always spelt it your way but half the European sites on the net spell it the other way. Anyway, "loupe" it is!


What Bob S. said.

And, it's "loupe".;) They don't work right unless you spell their name correctly.....:D