Question About Focusing Problem!

[rshorosky]

hello everyone,

i recently began shooting 4x5 after moving up from medium format and have been having difficulties getting fully focused negatives. initially i thought it may be the camera (toyo 45cf) but after a shooting with a different field camera i had the same results. when i scan the negatives the focus looks a bit soft for what 4x5 should look like and i am unsure as to the reason for this. as to my work flow i have ruled out most things as i am very meticulous when i shoot so if anyone has any ideas or suggestions to resolve the problem that would be great.

when shooting i always use a loupe to focus off of the ground glass and i mostly shoot at f32-64 so depth of field cannot be the problem. i also have used different film holders so i do not think it is a problem with the film holders either. so far my only theories as to the problem are possibly it being my eyes as i wear contacts, but have had someone double check my focus and that didn't really seem to be off), or the possibility of it being the way i am loading the film/ the film's plane in relation to the camera's plane?

if any would like i can upload a scan of one of the negatives for further help.
thanks again and any and all suggestions, comments, advice would be greatly appreciated!

sincerely,
ryan

[Robert Hughes]

It's possible your ground glass is not seated properly at the film focus point - or the film holder itself is not seated properly.

One way to test your camera's focus would be to photograph a ruler, laying on a table so that the scale runs away from the camera. Focus to a particular scale marking on your ground glass, expose and process, then view the negative with a loupe to see where the actual focus point is.

[rshorosky]

robert,

thank you for your reply. as to the possibility of it being the film holder, is there any way to tell if the holder is not seated properly without going through the process of photographing and checking the negative? i have never had a problem loading the actual holder onto the camera but is there a way to tell if when the holder is seated on the camera back that it is properly positioned?

[E. von Hoegh]

A scan would surely help. If you are comparing MF negs shot at f8 to LF negs shot at f64, the LF negs won't look too good. Diffraction at f64 will make them less sharp.

Is your loupe focussed on the GG? Do this with the lens removed, you should be able to see the texture clearly.

[E. von Hoegh]

robert,

thank you for your reply. as to the possibility of it being the film holder, is there any way to tell if the holder is not seated properly without going through the process of photographing and checking the negative? i have never had a problem loading the actual holder onto the camera but is there a way to tell if when the holder is seated on the camera back that it is properly positioned?

The ridge on the holder will seat in the groove on the camera back. You are loading the film under the little lips on each side, right?

[Robert Hughes]

You are loading the film under the little lips on each side, right?
I believe they are called "tangs". My kids love Tang! One of them breathlessly told me the other day, "You know, Astronauts drink Tang!"

[E. von Hoegh]

I believe they are called "tangs". My kids love Tang! One of them breathlessly told me the other day, "You know, Astronauts drink Tang!"


No, no, "tang" is the part of a knife blade that the handle is mounted on.
Tang commercial, 1970s

http://www.youtube.com/watch?v=Wf1kw5Yp9Ck

[rshorosky]

as far as the problem being within loading the film and loading the holder onto the camera i have had very little difficulty doing both and am sure i am loading the film properly as well as the holder onto the camera back.

as far as focusing while shooting, yes i focus the loupe directly onto the ground glass and have no difficulty doing so, so i don't think that would be the problem.

with refraction, would that throw the focus off of the entire image dramatically at f45/64 because when i look at my negatives even the objects/areas where i physically focused on through the gg are a bit out of focus.

[E. von Hoegh]

Diffraction, not "refraction" would soften the entire image slightly. Without seeing a scan, we're just guessing here.

[Gem Singer]

Ryan,

It's very possible that the ground glass on your camera is not in the same film plane as your film holders. Possibly a manufacturing defect.

In that case, it might need to be properly shimmed by a skilled camera tech.

There are methods to test for that problem, but it is not a simple matter to correct it.

If you're certain that the problem is not caused by your eyesight, the film holders, or diffraction, have the camera checked by an expert.

[E. von Hoegh]

as far as the problem being within loading the film and loading the holder onto the camera i have had very little difficulty doing both and am sure i am loading the film properly as well as the holder onto the camera back.

as far as focusing while shooting, yes i focus the loupe directly onto the ground glass and have no difficulty doing so, so i don't think that would be the problem.

with refraction, would that throw the focus off of the entire image dramatically at f45/64 because when i look at my negatives even the objects/areas where i physically focused on through the gg are a bit out of focus.

To clarify, diffraction limits the lenses ability to resolve fine detail. Stopping down increases the depth of focus, but limits the resolution.


http://www.luminous-landscape.com/tutorials/understanding-series/u-diffraction.shtml

[Dan Fromm]

Ryan, its easy to blame the camera, hard to blame the person behind it. From time to time I have what I've interpreted as severe problems focusing, as in every shot taken yesterday was out of focus. Here's what I do to eliminate the possibility of gear problems:

Find a nice regular brick wall.

Mark the intended point of focus on it, using something that will be discernible when I look at the negative with a 12x loupe or 20x stereo microscope.

Set up camera on tripod with the lens at a 45 degree angle to the wall and the mark in the center of the field. This will let me see where the vertical line of best focus is.

Make sure that camera and tripod are absolutely steady. In my case, this means checking the everything is tight, including the little Manfrotto set screws in the platform the head sits on and in the QR plate.

Shoot at f/8, f/11, f/16, f/22, using a long cable release. This lets me see whether the softness I interpret as poor focus is in fact due to diffraction.

Every time I've gone through this procedure the gear has passed and I've flunked. I've done similar things with focusing problems closeup, have got the same result.

I've uncovered faults in my setup and shooting procedures. Floppy tripod. QR plate loose in head (there are some counterfeit Manfrotto hex plates that are a tiny bit small). Too short cable release. Tripod on soft ground. Inadvertently kicking the tripod. Using too low powered a loupe (for me, a 12x works better with short lenses than a 3.6x). In closeup work, wind moving subject out of focus between set up and taking the shot (moral, don't even try) and unrealistic expections about DoF. Unrealistic expectations about the sharpness obtainable (at 12x everything looks a little soft).

Go at your problem systematically. You may find that your gear isn't right, but I think its more likely that you and your expectations are at fault.

Good luck, have fun,

Dan

[Bob Salomon]

To clarify, diffraction limits the lenses ability to resolve fine detail. Stopping down increases the depth of focus, but limits the resolution.


http://www.luminous-landscape.com/tutorials/understanding-series/u-diffraction.shtml

Not quite.

Stopping down increases the depth of field.
Depth of focus determines where the film lies to be in focus behind the lens.
Depth of field is the area of apperent sharp focus in front and behind the subject in front of the lens.

[John Berry]

My vote goes for diffraction. All a little soft? Something would be sharp in that image if it was focus. Vibration? I have had problems if trying to focus when real tired. Keep in mind that those that treat for glaucoma ( whether you have it or not ) will change internal pressure in the eye, effectively changing focus.

[jp]

Haven't heard a word about the scanning. Have someone else scan an image on their scanner or do an optical print to rule the influence on your scanner setup.

[Lenny Eiger]

Consumer level scanners produce blurry scans. Try a drum scanner to see what's possible. I would also suggest that wind can be a factor. Even a little bit can introduce some movement.
I don't worry as much about diffraction as I have tested my lenses (Sironar S) to f45 with great results altho' they do start to fall off a bit at 64... I'm with jp498, I think its probably your scanner...

Lenny

[jeroldharter]

I my experience with these gremlins, the problem is always my fault. In some ways, I would be pleased with an occasional mechanical problem.

Nevertheless, a couple of possibilities: You might be nudging the camera when you put in the film holder. If the spring mechanism is tight you are more prone to nudge the camera and would be out of focus.

Another option is that one of your adjustments is slightly out of wack. For example, I almost never used rear swing on my Canham DLC 4x5. So I did not notice that it was subtly of center for an entire trip. Even looking at the negs with a loupe they looked OK. But when I enlarged them they all went soft on the corners slightly. It took me a long time, several rounds of enlarger troubleshooting, aligning, etc. to trace the problem back to my camera. So your zero detentes on the camera could be slightly off also.

Also, is your tripod up to the task? You might be using an undersized tripod or tripod head so that the focus looks sharp but the negative is blurry because the camera is unstable. likewise if you hang objects from the center column to hold the tripod steady, they can introduce some instability if it is windy.

[dperez]

What about your loupe... Have you made sure that the diopter is adjusted correctly?

[Tim k]

How about you mail a negative to someone and have them print it on a known enlarger?