Slightly out of focus?

mealers · Oct 25, 2008

I'm having alot of trouble with all my 5x4 negatives being slightly out of focus, even printing on 10x8 you can see that each print is not quite as sharp as it should be.
I've pretty much ruled out errors made when enlarging. I always focus on the grain (with HP5) and I have also checked my negatives under a loupe and I can see they are OOF.
I did a test today where leveled the camera, set both standards so they were parallel, stopped down to f/32 and took an image of a brick wall. The result was the same as all my other negs, slightly OOF.

I have read that it is sometimes possible for the film plane to not be in the exact position as the GG?
How would I check this and rectify it?
I'm using Fidelity Elite, Astra and Toyo film holders.

I'm using a Shen Hao with 90mm SA and a 150mm Schneider Kreuznach

Has anyone got any ideas of what I'm doing wrong or how to fix the problem?

Many thanks
Mike

Ian Grant · Oct 25, 2008

Check the the film plane is the same as the Screen. Sometimes a screen etc is set for a plain screen, adding a fresnel shifts the plane of focus.

Ian

mealers · Oct 25, 2008

Thanks Ian
I dont have a fresnel on it, just the standard Shen Hao GG.

Mike

removed account4 · Oct 25, 2008

are your lens elements screwed in tight ?

mealers · Oct 25, 2008

jnanian said:
are your lens elements screwed in tight ?

Just checked them, they seem tight, I wouldnt want to do them any tighter.

I realise their are so many variables with this and I appreciate any input anyone has got.

Jon Shiu · Oct 25, 2008

Also make sure your enlarging grain focuser, if you are using one, is set correctly for your eyesight. That is, adjust the eyepiece so that the line is in focus.

Jon

Curt · Oct 25, 2008

I would suspect the Shen Hao back, If you make three exposures, one focused as you normally do, two focus as you normally would then focus slightly forward, very, very little, three do the same as two except focus and move backward. You will be defocussing forward and backward, if the ground glass is off, placed off the plane of focus then it will be obvious when you see them through the loupe.

I learned this at Brooks Institute of Photography in a seminar on focus for non removable focus screens in roll film cameras. You could use a dial indicator and measure the back without the ground glass in of course. My Mamiya 645 was off for years, just a little, until I learned how to test it, the results are stunning.

When I enlarge I put a piece of enlarging paper, the same brand as I'm using, under the magnifier.

Curt

Bob-D659 · Oct 25, 2008

Note, with the negative really out of focus. Also some/most grain magnifiers have two dark lines, you should be able to see the light line between the two dark ones. Young eyes are really adaptive in seeing the set lines and the image in a grain magnifier as both being in focus at the same time, when they are not.

Jon Butler · Oct 25, 2008

Mike,
If the unsharp negs are from different holders it may be the camera!?
What about movement - camera shake?
I'm sorry I sent you that print now.

Regards JON.

mealers · Oct 25, 2008

John Shui/Bob
Yep Ive checked the focus finder, I used it to print a 6x6 neg which was way sharper than my 4x5.

Curt
I think I'II try your idea tomorrow but if the film plane is too far forward or back then wouldnt that mean another part of the image should be tack sharp? The whole of the negative area is slightly OOF, not just the part that I focused on.

JON
Yep its all your fault, I was quite happy making crap prints until you sent me one of yours
My test shots today were taken on a good tripod/head and in no wind, ideal conditions really.

Curt · Oct 25, 2008

I'm sorry I forgot to mention that you should focus on a flat plane, a newspaper or magazine page, that's the important part, sorry to forget it. Tape up the paper on a wall and do the focus test on it.

Curt

bnstein · Oct 26, 2008

The other version of this is to take a sheet of print, lie on table and focus on one particular line. Keep lens pretty much wide open for narrow dof. Process neg and see where the sharp lines lie.

Curt · Oct 26, 2008

I forgot to mention that you need to shoot wide open when doing the focus test.

Curt

Lee L · Oct 26, 2008

Here's a test target that will show you where your focus lies relative to where you think your focus is.

http://focustestchart.com/focus21.pdf

It has instructions on use included in the file and the target to print is at the end.

There are also ways to make a "feeler gauge" to check that your film and ground glass are in the same plane. I'll see if I can find that online and post. Not sure I can explain it both clearly and succinctly.

Lee

Found a description of the method with photos by our own Jim Galli, referenced in another APUG thread. Here's Jim's page: http://tonopahpictures.0catch.com/ULF Back Measure/ULFMeasuring.html

mealers · Oct 26, 2008

I've just done my own pretty crude test and you can see the results below. I focused on the number 3 and as you can see the actual sharp focus is just before the 3.
This explains why my negs have'nt been as sharp as I'd like but wouldnt this mean that something in front of the point of focus would have been sharp instead??
What is the best way forward now?

Thanks
Mike

Ian Grant · Oct 26, 2008

Your test shows that the film is in a different plane to the screen, the screen needs moving back, away from the lens. Perhaps there should be a fresnel that would move the screen back, probably by the right amount. Other than that try making some shims out of card.

Ian

Lee L · Oct 26, 2008

How are you viewing the image on the ground glass when focusing the camera?

I'm also puzzled at how far out your focus must be to remain soft everywhere at f:32 when focused on a wall with either of these lenses.

Lee

keithwms · Oct 26, 2008

Dumb question: is your GG installed the right way around? The frosted side should face the film. Believe it or not, I have gotten GG backs in which the glass was installed incorrectly!

One other dumb / make-sure question: if you are new to 4x5, are you sure you're loading your film correctly? It should fit quite firmly against the backplate; with some holders it is fairly easy to load the film in a way that it isn't firmly seated but instead gets pushed in over the little side pockets. Load some film with lights on to make sure it is firmly seating.

Sorry if the above two points are insulting

Next, assuming it is, are you focusing with a loupe or by eye? What is your degree of confidence in the focus you see?

Next, after having satisfied yourself on these points, then consider the actual registration.

Ian Grant · Oct 26, 2008

Another question is what "150mm Schneider Kreuznach" is it a Symmar or a Xenar. The Xenar is a Tessar type lens on the optimum apertures for sharpness are f22 & f32.

It is just possible that there's a problem with the lens because the images should be sharp once stopped down even if the screen is slightly out of register.

Ian

mealers · Oct 26, 2008

Lee -I'm focusing with the aid of a x6 Silvesti Loupe, I have good eyesight and dont ware glasses.

Keith - No problem with the 'make sure' questions, I appreciate your help!
The GG is in place with the frosted side facing the lens.
I'm pretty sure I'm loading the holders correctly and not sliding them along the rails on the inside. I always touch both edges once the film is in just to make sure its lying flat.

Ian - Yep its the Symmar.
I get the same results with both lenses even stopped down to f/45.

One thing I have just done is ordered another GG from Brilliant Ground Glass, I'm hoping that it should help with critical focusing as I do feel the standard Shen Hao's is a little grainy.

Jon Shiu · Oct 26, 2008

Hi, you can make a gauge to compare your ground glass and film holder distance out of a ruler and a toothpick held on with a rubber band. Then, take the back off the camera and with the ruler across the back, push the toothpick until it touches the ground glass surface. Then insert a film holder with the darkslide out (and a piece of film in it) into the back and see if the distance is the same.

Jon

Ian Grant · Oct 26, 2008

Mike, I'd suggest you try and meet up with another Shen Hao user and try and compare notes. Something is not right, as Keith says DOF at f32/f45 should bring everything into focus anyway regardless of slight register problems, if there is any.

Ian

keithwms · Oct 26, 2008

One other issue is that I have seen is GG that is not polished / ground uniformly. I have a few cheap GG pieces that have radial bowing or even an overall warp, or they don't sit flat in the GG holder. Indeed, it'd have to be really bad to explain what you are seeing but, it is possible that the GG itself isn't flat. Why don't you check two things: (1) that the GG isn't bowed and (2) is sitting properly in the holder. You might well need to swap out the back and GG, if it wasn't manufactured carefully.

Ian's right, put another SH back on there from a colleague and see what you see. Maybe you got the unlucky back or a bum piece of glass.

Good luck, let us know how it plays out.

kirkfry · Oct 27, 2008

Do both lenses give the same result? Are you using the loupe on the the ground glass. Focus on something with depth of field, is something sharp? Look at the negatives, if the fuzziness uniform are are just the horizontal or vertical lines fuzzy suggesting movement. Rent or borrow another camera, are the pictures still fuzzy. Are you loading the film correctly? Let know how it comes out. K

Slightly out of focus?

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