Gg image in focus but resulting negative out-of-focus

[tonyowen]

135902135901

I’ve a Calumet CC401 4x5 cameras fitted with a Schneider Xenar f4.7 135mm.

I’m new to 4x5 work so I ’m just playing around getting use to the camera and lens.

Twice I’ve taken a picture (portrait is too formal) and on both times the resulting negative has the subject out-of-focus though the background is in focus.

However, in both cases the GG screen image was in focus (with and without using a 8x Agfa Lupe).

The camera to subject distance was around 1.5 to 2.0m.

The camera settings were 1/60s @ f7 (outside image) and 1/4s @ f8 (inside image).

I pretty certain the camera was not knocked or moved and I’m certain that the camera was not moved on its monorail.

Attached are scanned images of the (inverted) negatives.

Any observations and help welcome

Regards

Tony

[Ari]

Tony, what's happening is that your film holders are causing your film to be on a different plane than that of your ground glass.
Check them to see if there are any obvious problems, or if perhaps you loaded your film incorrectly. Maybe you seated the film holder improperly.
If they are old, worn out film holders, find or borrow a known good one from a friend or store, and make a comparison.

[jp]

Sometimes the groundglass+fresnel sandwich is reversed, causing it to focus on the wrong plane. Some cameras there are also clips for holding the GG and maybe the GG is installed in the wrong place? (previous owner repair issues)

[Old-N-Feeble]

Or someone may have replaced the GG/Fresnel... or removed a Fresnel... or added one. Any one of these will move the focus plane wrongly.

[Tim Meisburger]

Tony, take the back off, lay a straight edge across it, then measure down to the ground glass and record. Then insert a film holder with a scrap negative inside and repeat. The measurement to the negative should be exactly the same. If it is not, that is your problem. If it is, then check to make sure that the ground face of the glass is facing into the camera. If it is, then I am stumped. The face of the ground glass and the film should be on exactly the same plane.

[Jim C.]

First thought that comes to mind is the ground glass reversed ?
I had the same issue with a Century Grand, the gg image was sharp but the neg was out of focus.
The matte side of the gg should be facing inside the camera.

[Tim Meisburger]

No responses when I started writing and three before I finished!

[N Dhananjay]

Two possible reasons that occur to me.
1) Subject movement - have you tried making a photograph of something static to rule this out? I would suggest photographing a scale or ruler. Focus on, say, the 6" mark and see whether it is the 6" mark which is in focus on the neg.
2) Mis-registration of GG and film surface: When you put in the film holder, the film should be where the GG was, otherwise, there will obviously be focus errors. Especially if an after-market fresnel was installed the wrong way, it can mess up this registration. Some cameras were designed to have a fresnel on the inside of the GG and the registration was compensated accordingly, Most have a fresenel on the outside in which case, you could use a depth micrometer to check for whether the GG plane is the same as the film plane. I would start by ruling out 1 above and then proceed to 2.
There could be other more esoteric sources of focus error but I'd start here.
Good luck tracking down this gremlin.
Cheers, DJ

[AJ Edmondson]

The CC401 did not come from the factory with a Fresnel... should have been a gridded ground-glass (red lines). The matte side should face the lens and, if the GG has been replaced the orientation should remain the same. If the glass is reversed the plane of focus for the film plane will be displaced by a distance equal to the thickness of the glass. It will appear to be in focus to your eye but the film is registering forward of the plane.
Joel

[tonyowen]

The CC401 did not come from the factory with a Fresnel... should have been a gridded ground-glass (red lines).l
Thanks to all of the replies.
The ground glass has red lines - but whether it is the right way around I do not (yet) know
I'll follow all of your suggestions - I agree with the logic of all replies - now I have to test them one by one.
ps a correction to my initial posting the subject camera distance was 1m - which should no tmake any difference.
regards
Tony

[Ken Lee]

Note that the distance is in focus, not the subject or foreground. This means that the film is too close to the lens at time of exposure.

One possibility is that the camera back is slipping forward when you insert the film holder and remove the dark slide, because the rear is not tight.

Another possibility is that after focusing the camera - when you close the shutter and adjust the speed and f/stop - the front of the camera is slipping backwards towards the film, because the front is not tight.

If this is the case, you could determine this by checking focus after each step, without wasting a sheet of film. Just repeat each step and see if the focus has changed.

Of course, focusing on a stationary object rather than a person will improve your diagnostic precision.

[Peter Mounier]

I agree with Ken. Since the background from about 15 feet to infinity (guessing) is relatively in focus, you would have to move the rear standard about 10mm farther away from the front standard to focus on the human subject. 10mm is about the thickness of a film holder, which is about 10 times more than the thickness of the gg, eliminating gg orientation as the problem.
It's inconceivable to me how this could happen ... unless, while you had your head turned to retrieve the film to load it into the camera your subject surreptitiously moved several feet closer to mess with your mind.

I have a Calumet cc401 and the standards move on the rail via a friction lock. I can't imagine it moving or slipping 10mm on it's own while futzing with the lens or film holder without noticing that much movement. Even Stevie Wonder would notice that.

[tonyowen]

Synopsis of suggestions and my comments
1] Film holder & film incorrect
1.1] Film was inserted correctly notch right hand corner and emulsion side image is reversed.
Film holder misaligned – possible even probable.

2] The distance is in focus, not the subject or foreground. This means that the film is too close to the lens at time of exposure.
2.1 I do not understand – can anyone explain what this means in detail so it could be examined.

3] Camera slipping during film holder insertion and speed/f stop settings
3.1 Possible even probable – even though all movements were locked in their detente positions.

4] The rear is not tight.
4.1] Sprung loaded don’t know how to check correct tension.

5] groundglass+fresnel sandwich is reversed, Or someone may have replaced the GG/Fresnel... or removed a Fresnel... or added one. The CC401 did not come from the factory with a Fresnel... should have been a gridded ground-glass (red lines).
5.1] Fitted with gridded ground-glass (red lines), the matte side (rougher side) does face the lens.

6] Measure any variation of the distance between a datum and the ground glass screen. Repeat between same datum and the film in a dark slide holder.
6.1] Removed lens and measured to front of lens plate (??) Difference less than 0.5mm which could be due to springiness in the GG/dark slide holder mechanism.

6) Subject movement - possible even probable - however see below.
>>>>>>
7] I’ve checked the difference in extension for very close and distance subjects.
For 1m, 2m & c50m distance the measured extensions were 73mm, 58mm & 47mm. see image
7.1] These variations far exceed any ‘error’ due to film or film holder mis-placement.

8] According to my copy of Kodak Professional Photoguide (1975), the depth of field for a 125mm 4x5 lens is:
Distance to subject 2m.
F8 dof 1.7m to 2.5m
F32 dof 1.28m to 6m
>>>>>>>

9] I’m guessing that the problem is due to me not ensuring that the dark slide holder is correctly inserted and that the camera does not move.

Please comment
regards
Tony135916

[Peter Mounier]

If the dark slide holder wasn't inserted properly you would probably have light leaks.
Regarding your #2 question, as you focus on closer subjects the bellows widens and the front and rear standards get farther apart. Conversely, if you're focused in the distance, your standards are closer together, and the film is closer to the lens.

[tonyowen]

standards are closer together, and the film is closer to the lens.
you're right I was looking for complications in the reply rather than reading what was written!!
regards
Tony

[djdister]

Synopsis of suggestions and my comments
1] Film holder & film incorrect
1.1] Film was inserted correctly notch right hand corner and emulsion side image is reversed.
Film holder misaligned – possible even probable.

2] The distance is in focus, not the subject or foreground. This means that the film is too close to the lens at time of exposure.
2.1 I do not understand – can anyone explain what this means in detail so it could be examined.

3] Camera slipping during film holder insertion and speed/f stop settings
3.1 Possible even probable – even though all movements were locked in their detente positions.

4] The rear is not tight.
4.1] Sprung loaded don’t know how to check correct tension.

5] groundglass+fresnel sandwich is reversed, Or someone may have replaced the GG/Fresnel... or removed a Fresnel... or added one. The CC401 did not come from the factory with a Fresnel... should have been a gridded ground-glass (red lines).
5.1] Fitted with gridded ground-glass (red lines), the matte side (rougher side) does face the lens.

6] Measure any variation of the distance between a datum and the ground glass screen. Repeat between same datum and the film in a dark slide holder.
6.1] Removed lens and measured to front of lens plate (??) Difference less than 0.5mm which could be due to springiness in the GG/dark slide holder mechanism.

6) Subject movement - possible even probable - however see below.
>>>>>>
7] I’ve checked the difference in extension for very close and distance subjects.
For 1m, 2m & c50m distance the measured extensions were 73mm, 58mm & 47mm. see image
7.1] These variations far exceed any ‘error’ due to film or film holder mis-placement.

8] According to my copy of Kodak Professional Photoguide (1975), the depth of field for a 125mm 4x5 lens is:
Distance to subject 2m.
F8 dof 1.7m to 2.5m
F32 dof 1.28m to 6m
>>>>>>>

9] I’m guessing that the problem is due to me not ensuring that the dark slide holder is correctly inserted and that the camera does not move.

Please comment
regards
Tony135916

Tony - this is not the primary cause of your focus problems however in the photo you attached it appears that your front and rear standards are not precisely parallel to each other, which will definitely have an impact on your plane of focus.

[Jim C.]

No responses when I started writing and three before I finished!

HA ! All within a minute of each other !

[tonyowen]

it appears that your front and rear standards are not precisely parallel to each other, which will definitely have an impact on your plane of focus.
Thank you
Were not - now are
regards
Tony

[Tim Meisburger]

You are making it way too complicated. If the subject is in focus on the ground glass, and everything on the camera is locked down tight, and the subject doesn't move, but your picture is out of focus, the only thing it can be is that the film is not in the same place that the ground glass was in.

Also, when you focus, focus at your taking aperture to prevent any possibility of focus shift (that would seem unlikely unless your lens is mis-assembled).

[Andrew]

certainly looks like something is acting as a spacer and holding the GG too far away from the lens by a significant distance [I'm guessing it might be as much as 3mm to 5mm to generate that degree of focus shift]
it's most likely one of the possibilities that have already been mentioned like reversal of the GG or an improperly fitted Fresnel
but if the GG is correctly placed, is it possible that something's stopping the frame holding the GG from sitting properly in the camera back while your focusing?

[tonyowen]

Problem over - GG image and negative both in focus.
Took four images at close and very close range - all acceptable. (see one image from 1m distance
135983)
The only unknown is what happened with the two images that started this posting???
To try and ensure good focussing in the future I guess it is down to check, check and check again.
Thank you for all of your postings
Please be reassured that the information and suggestions were not wasted
regards
Tony

[gimenosaiz]

Hello!

Very useful post.
I've the same problem with my Pacemaker ...

Regards

[Jbuck]

edit

[tonyowen]

edit
??????? edit what ?????
do not understand unless you mean ditto
regards
Tony