90 mm lens & focusing screen

[alex sjoeberg]

Hello to all of you and many thanks for attention.
I am getting used with a borrowed 90mm (on 4x5) before the purchase of a new one. It is a Rodenstock Grandagon f6.8 not MC.
1/ I was surprised how different is the viewed image on my screen from what I knew (with longer lenses such as Schneider f5.6 120 or 150).
In addition to the 1/2 stop difference, the images comes much less evenly lit, in the way that I have to constantly move my head under dark cloth only to compose my shots (focusing with loupe more difficult as well).
Does it come with this particular lens ? Does it come from angle of view ?
As I may purchase a second hand 90 mm, I thought getting a f4.5 would minor the issue. And still hesitating to turn that investment into a Schneider 110 XL, would this one solve the issue ?
2/ Then, it may also come from the focusing screen I am using. (I couldn't even imagine the use of shorter lenses !!! ). It is a Beattie Intenscreen (used on Gandolfi Variant 4x5). Would this screen source the pb of dim viewed image « pain to compose » ? Should I come back to regular fresnel ? — thinking it would increase the problem. Or should I go to another enhanced screen ?

This lens will be the widest of the set (!) for architecture pictures — often in dim light. But I know many other photographers use mainly widest lenses (such as 72, 58 … ) with great results and accurate composition. Therefore I couldn't imagine them shooting with such bad viewing conditions. And I suspect the pb to come from my own configuration.

I would deeply appreciate anyone to enlighten the subject ! I'll be much interested in your experience of shooting architecture with wide lenses. Is it that hard to compose without moving head ?
Thank to all of you.

[Leonard Evens]

I have a Rodenstock 90mm f/6.8 Grandagon-N. Wide angle lenses will inevitably have significant fall-off in illumination towards the edges and corners. This will be excacerbated by a plain ground glass because of the way it disperses the light hitting it. The shorter the focal length, the worse the problem. It can be made a bit better by the the design of the lens, but not by a whole lot. It should be less of a problem with a 110 mm lens.

The real solution is to get a Fresnel screen which redirects the light rays back towards your eyes. You will be able to see the image better with such a screen. You can get addon Fresnel screens or others that are built-in to the screen. You should research that topic, since how one is installed can affect the place where the screen focuses compared to a plain ground glass. Shims could be required to avoid a shift in focus from gg to film. Some Fresnels may make it difficult to focus on very small detail with a high powered loupe. I got a screen from Maxwell Precision Optics to replace the gg that came with my camera. It provides a reasonably uniform field of view for focusing not only for my 90 mm lens, but also for a f/4.5 75 mm lens I obtained later. The image is also quite bright and I have no trouble focusing on small detail. Bill Maxwell makes screens to order. They are fairly expensive, but to my mind well worth the cost.

[Juergen Sattler]

Hi Alex,
I use that exact same lens and am very happy with it. There is no doubt that these wide angle lenses don't give you the same ilumination on the GG, but I don't have the problem you are describing. I am using mine on a Canham DLC45 with a Fresnel screen and I can see the entire GG-image without moving my head around. I have no experience with the Beattie screens. I have used that same lens on a Technika and a Sinar F1. The Technika without a Fresnel was tricky and I did have problems seeing the entire image - so maybe it is your screen.

[Matthew Cromer]

I have a beattie screen and a 65/8 (actually more f/5.6ish) and indeed have to bob my head way far all around to see the entire image. This seems to be a characteristic of the beattie design and wide lenses. One option is a second back with a screen specifically designed for wide lenses, and swap out the back when you go wide. This is usually a quick operation on many field cameras.

[John Gittens]

Hello Alex, It does not matter that much that you cannot SEE as well the sides of the image on the ground glass - what does matter is something that no-one above has mentioned. You need to stop down the aperture (after focussing) to at least F16 to get an overall even density on your film , ESPECIALLY if shooting chromes. One can buy a special filter (specifically for the lens you are using, cannot interchange for other focal lengths) that evens out the light but they are also very expensive. The least expensive way is to stop down the aperture. As long as you can see the image edges enough to align the camera, do not worry about not being able to see even density when focussing.

[alex sjoeberg]

Many thanks to all of you.

I do have found extra infos and it seems that the Beattiescreen mainly sources the COMPOSING problem I mention (creates a « hotspot » when using wide angles). I believe a Maxwell HI LUX screen might give far better results (I mean « viewing »).

I do care to see my image for composing, and not only edges one after the other just to align the camera then shoot and check on polas then shoot ! (And I haven't yet shot 4x5 architecture more open than f22, but AFTER COMPOSING AND FOCUSSING).

Well pleased with this Rodenstock 90 f6.8 … I'm gonna try the 110 XL then. And I'll go further to solve that SCREEN issue as well. Has anyone inputs about screen contest for wide angle lenses ? Beattie vs Maxwell HiLux ?

Cheers again and good shots (And I keep thankfull to such a help this forum gives)
Alex

[Brian Ellis]

I've used all available screens. For a 90mm lens the best choice is a Maxwell screen. The next best choice is a BosScreen. Nothing else is even worth mentioning, Beattie screens and other Fresnels are no good for short focal length lenses (unless the screen is a Maxwell or is specifically designed for short focal length lenses). I seldom say anything with such certainty but I really have used everything from three or four brands of plain ground glass, Fresnels of various makes (OE on Ebony and Tachihara cameras, Beattie on another camera), BosScreens on 4x5 and 8x10 cameras, and Maxwell on my present Master Technika. Maxwell is the best of the bunch, I can easily see the entire image on the screen when using an 80mm lens, BosScreens are next, nothing else is even close for short focal length lenses.

[KWSmith]

To me, a 90mm isn't particularly wide or difficult to focus. I don't know what kind of camera you have but if it's a Sinar, their fresnel and magnifying bino hood really, really help. Even 55-75 lenses aren't all that hard with that accessory, but the only way to -know- if you're sharp is to loupe a Polaroid neg.

[John Gittens]

Hello again, We agree with KWSmith - did not think to ask if you possibly had a Sinar - using the Binoc hood works very well for all lenses including the 90mm & the 65mm plus the image is viewed the correct way up though reversed horizontally. Do not know if you can get one of those for other makes of camera.

[KWSmith]

I only use the straight bino thing, not the reflex viewer, which is bulky (and expensive). I've gotten so used to the upside down thing that I don't even notice it anymore.