LF F2.0 "compose lens"?

Hi all,

Just yesterday tried to make some night LF (4x5) photos again. Now I have done this before, but I was again reminded of how much a pain this can be.

Even though all my 3 lenses (75,150 and 210) are F5.6, composing and focussing can be a real pain at night . The image on the ground glass is just to dim, especially with 75 mm lens.

I know there are other types of groundglasses, but I have already tried an alternative, and wasn't convinced it made a real difference compared to the standard one that came with my Tachihara.

The real problem is of course, we need faster lenses!

Now this is probably going to be nothing more than some stupid fantasy, but I wondered if there couldn't be something like a cheap, for all I care made from plastic, F2.0 "compose lens", a lens that I would use for nothing else but composing (and maybe focusing) my images, that I would "swap out" for the "real deal" when I would make the picture.

To me, the only thing such a lens would have to do is: be light (so probably plastic), so as not to put in to much extra weight, have an accurate focal length and not much more. No need for an expensive shutter, no need for an adjustable aperture, no expensive chromatic aberration corrections, anti-reflection coatings, or perfectly distortion free, no need for anything but throwing a bright image on my groundglass!

Since the standard lensboard of most cameras is about 8-9 cm wide, we could have a F2.0 150mm lens, or even F1.0 75mm one

Of course, I realize I would need a new "compose lens" for each focal length I have...

Anyway, it is all probably complete nonsense, and I know little about optics, but sometimes it is nice to dream of a "perfect world"

What are you trying to shoot at night? There may options besides lenses.

In the film "Henry and June" there's a great scene recreating Brassai making some of his images from "Paris by night". He focused by scale, and a tape measure, this is one area where a press camera with a finder might be better.

Ian

Hi

I had the same problem but I came to a rather easy solution. I got a really powerful flashlight and a "grip arm" which holds the flashlight when i am focusing. When everything is in focus i turn the flashlight of and shoot the picture.
You have some really powerful, like http://www.wickedlasers.com/lasers/The_Torch-74-41.html , now mine is not that powerful and i only paid 50 CHF, but still, can easily focus on objects 300 meters away.

cheers

I guess focussing with substitute lens won't work perfect as even nominal FL may not reflect actual FL.

Have you thought about using flashlight (continuous lighting of course) for focussing?
Or you could use a laser rangefinder and scale focussing for non-swing work.

jp498 said:

What are you trying to shoot at night? There may options besides lenses.

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You mean this :confused:



No, I am innocent, it wasn't me who robbed your local bank last night!... :rolleyes:

AgX said:

I guess focussing won't work as even nominal FL may not reflect actual FL.

Have you thought about using flashlight (continuous lighting of course) for focussing?
Or you could use a laser rangefinder and scale focussing for non-swing work.

Click to expand...

I occassionaly use a small LED light for focussing. I put the LED light at the point I want to focus, focus then, and remove the light again before the exposure. Works reasonably well.

The real problem is more with "composing" versus "focussing". Is the image "straight up", are there any distracting elements at the borders of the frame?... It is hard to see sometimes!

Well, that focal lenght difference between composing and taking lens could be handled with an adapting focussing scale that relates the extensions of both lenses.

sandholm said:

You have some really powerful, like http://www.wickedlasers.com/lasers/The_Torch-74-41.html , now mine is not that powerful and i only paid 50 CHF, but still, can easily focus on objects 300 meters away.

cheers

Click to expand...

OMG!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! :eek::eek::eek:

[video=youtube;wsIHyRyETKg]http://www.youtube.com/watch?v=wsIHyRyETKg[/video]

Imagine this thing accidentally switching on when in your trousers pocket...

Marco

In principle a simple 1-element lens would work, but don't forget about field curvature and such.

AgX said:

In principle a simple 1-element lens would work, but don't forget about field curvature and such.

Click to expand...

What is field curvature exactly? Does it mean the focussed plain is not flat, so no in-focus image across the flat plain of the groundglass or so??

Yes.


Are plastic lenses of the needed FL and diameter accessible?

For composing at night, I'd probably first try the wire frame popup sportfinder on my speed graphic's front standard. Should work with some variety of lenses. Next would be the optical viewfinder that sits on top. Probably neither would be ideal for big tilts or shifts, but that could be tested ahead of time in daylight.

AgX said:

Yes.


Are plastic lenses of the needed FL and diameter accessible?

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Well, there are at least companies specializing in it:

Dead Link Removed
http://www.polyoptics.com/
http://www.plasticoptics.com/
http://www.anchoroptics.com/catalog/product.cfm?id=152
http://njaili.en.made-in-china.com/product/emxnAvfTRJSd/China-Plastic-Lens.html

And a whole inventory of companies doing custom plastic object engineering and manufacturing, some of it lenses:
http://www.thomasnet.com/products/plastic-lenses-43880806-1.html

But I wouldn't have a clue what to buy to have a decent image...

Marco

jp498 said:

For composing at night, I'd probably first try the wire frame popup sportfinder on my speed graphic's front standard. Should work with some variety of lenses. Next would be the optical viewfinder that sits on top. Probably neither would be ideal for big tilts or shifts, but that could be tested ahead of time in daylight.

Click to expand...

That is a good one, never thought of that... but than I don't have speed graphic and never used such a wire frame or viewfinder for LF. I also think I need to get a couple of good water levels for my camera, so as to be sure it is straight up. Anyone know where I can buy good small water levels to glue on my Tachi?

I'd go with a zoom viewfinder like Horseman or Linhof made.

ic-racer said:

I'd go with a zoom viewfinder like Horseman or Linhof made.

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Are they good enough to judge for aligning? Again, I have never used them. It sound interesting, but it would be nice to know if they are accurate enough for seeing proper alignment with vertical / horizontal lines in the composed image, like walls of buildings.

Should be OK for alignment, but only if the camera has a fitting to attach one.

Ian

My vote is for the wire-frame finder, like one finds on Speed Graphics.

An alternative is the "viewing lines" or "viewing dots" method used by pinhole photographers with box cameras. A triangle is outlined, on the camera's top and side, with the apex of the triangle adjacent to the lens, and the two other vertices adjacent to the edges of the film plane. You compose by line-of-sight, horizontally and vertically, and it can be surprisingly accurate.

Don't over-complicate or over-engineer things with homemade optics, instead go with the elegant simplicity of a wireframe or viewing lines method.

~Joe

I think someone at LFF has a couple of inexpensive magic lantern lenses around f3, don't remember the fl's though.

The Linhof zoom finders have parallax correction. They take some getting used to, but you can frame fairly accurately with one. I've used both the old style and the more modern style.

Of course the groundglass is more accurate, if you can read it.

Have you tried a fresnel on top of your ground glass? I have one on my Sinar F and it works pretty well.

Having an assistant with a powerful lamp is of great help. In many cases you can shine the lamp yourself, but an assistant helps a great deal, IME. Rangefinders and zoom finders would work fine if you could find something with enough contrast to focus on, and if you don't need to use your camera's movements.

Possible solutions

David A. Goldfarb said:

The Linhof zoom finders have parallax correction. They take some getting used to, but you can frame fairly accurately with one. I've used both the old style and the more modern style.

Of course the groundglass is more accurate, if you can read it.

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Thanks, good to know the zoom finders are accurate and useful. May try one. I also saw more affordable "no-brand" zoom finders on e-bay that may be worth a try once.

Mainecoonmaniac said:

Have you tried a fresnel on top of your ground glass? I have one on my Sinar F and it works pretty well.

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Actually, although the Tachihara is a cheap camera, the GG is fairly well. It seems to incorporate fresnel type grounding. I compared it with a normally ground GG that was advertised as being good, and had the feeling the Tachi beat it in terms of overall illumination, especially along the sides. But even so, it still isn't enough...

Joe VanCleave said:

Don't over-complicate or over-engineer things with homemade optics, instead go with the elegant simplicity of a wireframe or viewing lines method.

~Joe

Click to expand...

I agree, especially now Ian C posted me an interesting proposition in two PMs. I have included the text below. Essentially, he suggests turning the whole camera itself into one giant light gathering "viewfinder" using some mat board and tweaking/calibration.

Although the first PM shows some more complicated math, the second PM gives the general concept. Essentially it is nothing more than a piece of carton in place of the GG with a small hole acting like viewfinder, and the front lensboard replaced by a piece of card board with a hole cut out the same dimensions as the film format.

Seems like a low tech solution worth trying out, that may give slightly more accurate results than a wire frame on top of the camera. Will be nice trying out and creating something. I like messing around a bit.

By the way, thanks all for the responses! What started out as only a half serious question, as I didn't expect a real solution to this problem to turn up, turned into a serious discussion of multiple workable solutions. APUG again amazed me!


*** FIRST PM by Ian C ***
I think that there might be a simple solution to your problem of composing night scenes. You’d make a simple viewfinder to temporarily take the place of your ground glass back. It will be a flat plate that attaches to the back of the camera as the GG back does.

On center there will be a tube extended rearward giving you sufficient clearance with the plate for you to place your eye close to the small opening, perhaps 10mm or less in diameter, in the tube. You’d leave the lens board off and adjust the distance from the lens of your eye to the lens board opening to approximate the angle of view of whatever lens you’re using. The adjustment will be made by moving the standards along the rail or bed.

For a wide-angle lens, such as a 75mm lens on the 4” x 5” format this should be particularly easy since you’ll likely use it at, or close to, infinity focus. Measure the diagonal of the visible opening formed by the front bellows & lens board frame and call it y.

The forward angle of view of the lens is generally given in the maker’s data. For example, for my 75mm/4.5 Nikkor SW it’s: 80° at f/4.5 and 106° at f/16.
Let x = the distance from the lens of your eye to front frame. Then

x = y/[2*tan(ϴ/2)]

For the 75/4.5 Nikkor SW at f/16 and assuming a 150mm x 150mm opening in the front frame the diagonal is 212mm. Then

x = 212/[2*tan(53°)] = 79.9mm.

To adjust the viewer for close focusing you’d need to calculate the bellows increment Δ as

Δ = f^2/(p – f)

At 1 meter p = 1000mm, so Δ = (75mm)^2/(1000mm – 75mm) = 6.1mm. So x must be increased by 6.1mm at 1 meter so that the viewer will properly restrict the view.

You could likely forego the math by calibrating the viewer in daylight and simply recording x for whatever lens is in use and the camera to subject distance into a handy pocket notebook.

Focusing is a separate issue that can easily be dealt with by translating camera-to-subject distances into a table of corresponding distances from the rear of the GG back to the front of the lens board. These are easily measured with a roll-up steel millimeter scale or a dressmaker’s cloth measuring tape. For night work a small pocket flashlight is required as well.
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*** SECOND PM ***
To use your camera for night photography first gather some measurements in the daylight. Set up the camera and lens and compose a scene with your favorite lens and note the left, right, top, and bottom limits of the view and record the GG to lens board distance.

Now remove the lens, GG back, and replace the back with the custom-made plate and eyepiece aperture as discussed yesterday. You need a stand-in for the lens board—matt board would work fine—mounted in the front frame.

It should have a window of the same aspect ratio as the film cut out of the center and oriented the same as the back was. Move the standards forward or back until the view matches the limits you saw through the lens. Measure the distance from the back of the rear frame to the front of the front frame and record this in your notebook.

When you shoot at night you first set up the camera as a viewfinder and use the viewfinder dimensions in the notebook for that focal length. What you see is what you’ll get when you shoot with the lens installed. With no lens or GG in the way the view is as bright and contrasty as it can be.

After composing the view you can install the spring back and the lens and then duplicate the focusing dimension you recorded in daylight with a millimeter scale. A small pocket flashlight to read the scale will make setting up the bellows draw easy. You’ll need one anyway to set the aperture and shutter.
**************

You could get some night vision goggles.