Disappointing results with my Crown Graphic

[tim48v]

I've just started playing with a Crown Graphic with a Schneider-Kreuznach symmar 150mm/f5.6 lens.
I just can't seem to get a really "sharp" image.

I've attached some samples. These where shot on a tripod, f8, 1/100 (which is closer to 1/75 with this lens), 4x5 Fujifilm RVP 100F. The cropped sections are 1:1; I had to reduce the file size of the full image in order to upload.

I'm focusing on the gg (the range finder is missing the "plungers") using a magnifier. Images scanned on a Epson scanner at 4800dpi.

The only other issue: the ground glass is cracked but seems to be tight against the Fresnel lens. When I first got the camera the gg was between the Fresnel lens and the camera lens, (images were really fuzzy). It's now setup: lens > smooth side Fresnel > rough side of gg (the two rough sides are against each other).

I was expecting the images to be a lot sharper; am I expecting too much? Frankly, my Century graphic blows this away.

Any suggestions would be appreciated.

 

[BAC1967]

The rough side of the ground glass should be closest to the lens, the same place as the film plane. Do you use a loupe to focus? You should be able to get very sharp images.

 

[rrocco]

Don't think the focus is your problem. You have your foreground and background both out of focus and the barn is in focus (though details are not sharp). I think your problem probably lies within the lens or technique. To test the lens you'll want to take a picture at a smaller aperture. This will increase your depth of field and sharpen the image. Another issue related to the lens may be due to shutter vibration or vibration in taking the photo. Try to use a higher shutter speed, use a shutter release cable and very importantly a heavy/sturdy tripod. Don't give up. With your setup and good technique you should be able to achieve astonishing sharpness and detail.

 

[RobC]

I don't think you'll get optimum performance with that lens until you close down to f11 or smaller. I would not use f8 except in exceptional circumstances. The corners won't be sharp. And DoF will be much greater as already stated.

 

[shutterfinger]

This is where an inexpensive B&W film such as Arista EDU Ultra 400 will shine. http://www.freestylephoto.biz/190415-Arista-EDU-Ultra-400-ISO-4x5-25-sheets The faster film will show exposure errors quicker, light leaks quicker, and allow faster shutter speeds or smaller apertures than a ISO 100 film.
1st. check the gg assembly- fresnel smooth side toward the lens in front of the ground glass with the smooth side of the ground glass facing you. Make sure that the gg/fresnel sandwitch is seated properly on the bosses of the focus panel.
2nd. Check that any film holder is seating properly into the back. Remove any build up from the end corners and the light trap grove.
3rd. Set the camera up on a tripod and site down a fence or textured wall (brick works well) at an angle without using any camera movements. Center the image on something that will be easy to distinguish in the negative. Attach a tape measure to the wall if possible so that there is equal scale either side of the center point. Loupe focus on the center of the image. Make an exposure at f5.6.
4th. Process the test exposure and examine the negative with a loupe. Is the center point you focused on the sharpest in the image? Yes-the gg/fresnel is at the surface of the film as it should be. NO- The gg/fresnel needs to be shifted to match the film surface. Point of focus is further forward of the center point- gg/fresnel needs to be shimmed toward the film plane. Point of focus rear of the center point- gg/fresnel needs to move further from the film plane.
5th. Mount another lens on the camera and repeat the test. Sharp image obtained suspect the Symmar to have incorrectly assembled cells or incorrect spacing between cells or to be a soft lens. Soft image obtained is camera shake/vibration from your tripod/head combination or a problem with the front standard of the camera. Is there any play in the front standard when locked? Is there any side play in the rails? Does the focus lock work? With the lens at infinity, focus lock set, camera pointed down at 90° does the rails stay put or do they creep forward?

 

[RobC]

You didn't notice the colour in those images then...

 

[Ian Grant]

If the previous owner added a fresnel to a back designed for just a plain screen then it would be correct if fitted if on top of the screen (not lens side), that's how I have to use a fresnel with my Crown Graphic (spring back).

The problem is the GG frame holders are the same castings for both the frames machined to take a Fresnel as well as the GG and those for just plain GG screen, it's just the machining that's different. Both the Graflex spring backs and the Graflok backs came in the two types, I have a Graflok back on mt Pacemaker Speed Graphic and both types of GG screen holder, focus is identical with the plain GG or the GG & fresnel, Side by side the difference between the two is subtle but with the screens etc removed the one that takes the fresnel is deeper from the back to where the fresnel, then GG, sits. I should get my vernier out and measure the differences.

LF lenses are optimised for f22 so don't expect too much overall sharpness from wider apertures. I shoot with a Crown Graphic or Super Graphic with either a 135mm f5.6 Symmar or a 150mm CZJ f4,5 Tessar, and sometimes a 90mm f6.8 Angulon with great results. With the Tessar edge sharpness falls off as you use wider apertures, fine for portraits etc but not always for landscapes.

Are you using a tripod ? I do shoot hand-held in Turkey & Greece when tripods aren't allowed but always with HP5 and usually that allows 1/200 at f22.

I'd check out your GG screen holder and make sure that's not the issue. It wouldn't take me long to dis-assemble and measure the two Graflok focus frames. Welcome to APUG BTW.

Ian

 

[shutterfinger]

The difference in "boss" height was discussed on http://www.graflex.org/helpboard/ a few years ago. It should be in the Speed Graphic help section. The boss for a fresnel designed back will have low bosses and one for a ground glass only will have high ones. I do not remember the heights or the post title/subject it was posted in.

Oh, yes, was those photos made late in the afternoon or is that cast just fudgeies over saturated standard?

 

[RobC]

LF lenses are optimised for f22 so don't expect too much overall sharpness from wider apertures.

Well this depends on the particular lens and the later/current versions of the 150 are quite good from f11 and smaller apertures. F16 is probably optimal but for being sure its sharp to corners then f22 is usually a safe bet. Also depends on focal length.

 

[Neal]

Dear tim48v,

First, have no fear, you will solve the problem.

You have the ground glass and Fresnel in the correct orientation. If the image on the ground glass was sharp during focusing, your image should be sharp.. it is possible that the front standard shifted after focusing. Maybe the clamp to hold the rails in place is not working properly. Keep in mind that f/8 will give you a very shallow depth of field.

You are correct that the images should be sharper.

Good luck,

Neal Wydra

 

[Ian Grant]

You have the ground glass and Fresnel in the correct orientation.

As I said above that may actually be incorrect if the focus screen frame wasn't made to take a fresnel. Used incorrectly the results would be as described by the OP.

Ian

 

[Sirius Glass]

You have been give so really great advice. Step by step check out the focus on the ground glass and see if the ground glass needs to be replaced. I think that the focus will get better when you use a aperture f/11 or smaller.

 

[shutterfinger]

On a Graflex Graphic cameras the rear surface of the ground glass will be flush with the frame and the view hood will just close over it. Fresnel installed on a ground glass only back will put the rear edge approximately 2mm above the frame edge and prevent the view hood from closing. A ground glass only in a fresnel designed back will put the rear edge of the ground glass recessed into the frame approximately 2mm and will not affect the view hood operation.

 

[Ian Grant]

You can easily measure the depth from the back of the focus panel to the rear of the GG for 4x5 film this is the T distance should be 0.197" (5mm) +/- .0072" (0.18mm). Note this is the correct distance for a plain GG screen or where a fresnel is also used on the rear. Some manufacturers used a fresnel on the rear (outside) of the GG, my Cambo Cadet's fresnel was like that, it was also very thin.

When a focus frame is designed for a fresnel under the GG the T distance is less to allow for the thickness of the fresnel, but as this is effectively a a lens the actulay difference is closer to half the fresnels thickness, somewhere around 1 to 1.2mm.

Ian

 

[Ian Grant]

On a Graflex Graphic cameras the rear surface of the ground glass will be flush with the frame and the view hood will just close over it. Fresnel installed on a ground glass only back will put the rear edge approximately 2mm above the frame edge and prevent the view hood from closing. A ground glass only in a fresnel designed back will put the rear edge of the ground glass recessed into the frame approximately 2mm and will not affect the view hood operation.

I needed to shim the clips on my Crown Graphic when I added a rear fresnel, the clips will fit OK without but the focus hood won't lock in place securely without the shims.
just use a good pair of glasses
The OP's issues remind me of a friends issues with a brand new Chamonix a few years ago, it was a new model the first to come with a factory fitted fresnel but he couldn't get sharp images, portraits at wider apertures. It turned out it was a design fault, the factory hadn't taken into account the 2mm thickness of the fresnel and adjusted the back dimensions to compensate, the company did rectify the problems.

A fresnel on the rear isn't ideal, the one I had for my Cambo Cadet was the best rear fresnel I've used, I don't use a loupe with my Crown Graphic preferring to use a good pair of glasses, I don't think a Loupe works well with most fresnels rear fitted, if you want to use a fresnel then plain GG is by far the best option but it's a lot dimmer with no fresnel.

Ian

 

[tim48v]

Everyone,
Thanks for all the comments. The question I really wanted answered has been answered: is something wrong? Yes, there is.

Regarding the gg/fresnel fit: the viewing hood closes fine. I've measure this before (which is how I figured out the gg/fresnel were installed backwards). I rechecked it today, the fresnel is .069" thick and the distance from the mounting plane to the front of the fresnel is .141"; since the rough side of the gg is against the fresnel, it's .210" from the mounting plane. I've measured several film holders and they're all about .210 from the mounting plane to the film plane. (This doesn't account for the thickness of the film.)

I measured my 120 roll film adapter and it's only about .200" from FP to mounting point. I may shoot a roll with it as a test case. (I've never used it.)

I wonder if this is a camera shake issue since nothing is in focus? They were all taken on a tripod but not a great tripod.

Going forward:
I'm going to shoot some "angled fences" to see if anything is in focus.
I'll also take some photos using the self timer and higher lens speeds.
I have another lens Carl Zeiss Jena 13.5cm/f4.5; but I don't think this is a lens issue, but I'll play with it.

Forgot to mention, barn016 waw shot at sunset; barn017 at sunrise.

Thanks again,

Tim

 

[Sirius Glass]

Oh yes, welcome to APUG

 

[RobC]

You can do a focus test by using a ruler and photographing it.

Place ruler horizontally on a table and then tilt it up approx 30degrees and photograph it. You can then see whether the part of ruler you focussed on is sharpest or whether you have near or far focus.

Ideally I would put center of ruler approx 1 meter from lens (this will be a macro shot with significant lens extension)

For a 150mm lens at f5.6 assuming a CoC of 0.0088 (theoretical smallest possible) then for that CoC you will get approx:

Depth of field: 3.72mm
Depth of focus: 0.058mm

For a 150mm lens at f5.6 assuming a CoC of 0.03 (usual target CoC) then for that CoC you will get approx:

Depth of field: 12.69mm
Depth of focus: 0.198mm

But I do think that just closing down 2 or three stops from f8 will make a big difference to resolution and sharpness.

 

[Jim Jones]

. . . Regarding the gg/fresnel fit: the viewing hood closes fine. I've measure this before (which is how I figured out the gg/fresnel were installed backwards). I rechecked it today, the fresnel is .069" thick and the distance from the mounting plane to the front of the fresnel is .141"; since the rough side of the gg is against the fresnel, it's .210" from the mounting plane. I've measured several film holders and they're all about .210 from the mounting plane to the film plane. (This doesn't account for the thickness of the film. . . .
Tim

You need to allow for the index of refraction of the Fresnel. This should place the film slightly closer to the lens than you expect. Also the so-called T-distance (the distance from the face of the film holder to the septum against which the film is backed) is given as 0.197 +/- .007 inches in the old ASA standard which I believe is still valid. You can make one test shot as RobC suggests above, measure the error on the target, and calculate any correction needed to place the ground glass and Fresnel at the right distance from the face of the ground glass frame.

 

[Ian Grant]

LF cameras are quite prone to camera shape due to their size, mass helps but the Crown Graphic is quite light so needs a sturdy tripod. Where you using a cable release ? That's as effective as using the self timer on the shutter.

Your CZJ 135mm f4.5 is presumably a Tessar it just covers 5x4 but edge and corner sharpness drops off very quickly as the aperture is opened, it's best at f22 but even at f16 corner sharpness is noticeably less. I've used one quite a bit and there's no room for movement but used carefully quite a capable lens.

Ian

 

[RalphLambrecht]

Well this depends on the particular lens and the later/current versions of the 150 are quite good from f11 and smaller apertures. F16 is probably optimal but for being sure its sharp to corners then f22 is usually a safe bet. Also depends on focal length.

I agree for 4x5 lenses, f/16 is a good compromise between abberation anddiffraction

 

[tim48v]

I'm thinking more about the "index of refraction" of the Fresnel lens. Both Jim and Ian have mentioned it and it implies that there should actually be a difference of around 1mm (0.040") between the location of the gg and the actual film. I've been trying to get them to match exactly.

When I got the camera, the Fresnel and gg where in a different configuration (I think the Fresnel was on the outside, farthest from the camera lens, rough side out, but I'm don't remember.)

Were Crowns ever built in a different configuration? I'm sure that someone has been messing with this one before I got it; I have no way to know if it's the original Fresnel or not.

 

[RalphLambrecht]

this may help but file size limitation won't allow me to post it. Send me an email request to rlambrec@ymail.com to get the file.

 

[Ian Grant]

I'm thinking more about the "index of refraction" of the Fresnel lens. Both Jim and Ian have mentioned it and it implies that there should actually be a difference of around 1mm (0.040") between the location of the gg and the actual film. I've been trying to get them to match exactly.

When I got the camera, the Fresnel and gg whe(there was a url link here which no longer exists)re in a different configuration (I think the Fresnel was on the outside, farthest from the camera lens, rough side out, but I'm don't remember.)

Were Crowns ever built in a different configuration? I'm sure that someone has been messing with this one before I got it; I have no way to know if it's the original Fresnel or not.

No, they either came with a back adjusted to take the glass with the fresnel underneath or for just a GG screen.

I've just measured the T distance and on the Graflok plain screen back it's 0.173", and with the Graflok back with the original Graflex fresnel it's 0.143", it's quite a noticeable difference when they are seen side by side. The original fresnel is 0.080" thick, it's more than just the bosses that are deeper the inner edges the fresnel sits on are thinner as well.

Ian

 

[tim48v]

Just so I'm clear, here's a photo of what I think we're calling the "T" distance. It measures 0.141". Also, my Fresnel is only 0.068" thick.