A Focusing Problem? Please help.

Keith Tapscott · Post by **Keith Tapscott** » Tue Apr 22, 2008 2:30 pm Etc/GMT-1+01:00

I have finally had some of my 4x5 negatives enlarged onto 16x20 paper by a photographer who lives locally to me. He sent the prints back to me with a note saying that the negatives look to be of good quality concerning exposure and processing but the image on the print looks slightly soft overall.
The photograph is on 4x5 T-Max 100 and taken with a 180mm Symmar-S on an MPP Mk VIII. I used a Toyo 3.6X focus-aid on the screen to ensure that the main part of the subject was in sharp focus, but even this is on the soft side on the enlargement. What am I doing wrong?

I don`t get this problem on 35mm or 6x7 MF, so help and advice needed.

Post by **Joanna Carter** » Tue Apr 22, 2008 2:37 pm Etc/GMT-1+01:00

Hi Keith

The obvious first question is, if the image is tack sharp on the GG screen, then the film may not be resting at the same distance from the lens as the screen.

The easiest way that I can think of checking this would be to take a shot of a ruler, set at an angle, focusing exactly on, say, the six inch marker; if, upon processing, any other mark on the ruler is sharper then your GG screen is not set at the correct position to match the film plane.

There may be more (and/or better) ideas from others

Keith Tapscott · Post by **Keith Tapscott** » Tue Apr 22, 2008 2:55 pm Etc/GMT-1+01:00

I will try that Joanna, should I shoot with the lens at open aperture, or a series of exposures gradually stopping down? Also, if the 6" mark still isn`t quite sharp, how do I correct this problem?

Thanks,

Keith.

Post by **Joanna Carter** » Tue Apr 22, 2008 3:18 pm Etc/GMT-1+01:00

Keith

You need to shoot wide open to minimise the depth of field.

If the 6" mark is not sharp, then this will indicate that the GG is not correctly positioned. With most GG holders, it is not too difficult to pad out the screen but not so easy to get it closer to the lens. If everything about the camera seems tight and straight then this would indicate that the GG may have been assembled incorrectly; otherwise "moving" the GG would be your only option.

percepts · Post by **percepts** » Tue Apr 22, 2008 4:32 pm Etc/GMT-1+01:00

This is a good idea in theory BUT what you are doing is taking a macro shot of the ruler. At those focus distances the depth of field is very narrow. However, the depth of focus is large so that a small change in GG position shows indiscernable difference in neg. Also does not tell you how much you need to adjust the GG. And its impossible to measure lens to subject distance and lens to film distance accurately enough to be able to calculate amount to adjust GG accurately.
It's simpler and more accurate to measure GG depth and film holder depth and compare them which tells you how much adjustment is required.
Also depth measurement also shows if you have parallelism of the GG which photographing a ruler doesn't.

Post by **Paul Mitchell** » Tue Apr 22, 2008 4:55 pm Etc/GMT-1+01:00

Keith

I had a similar problem with my first negs, I had a soft area only on one part of the image, turned out that I didn't load the film into the DS properly... just a thought?

Paul

Paul. · Post by **Paul.** » Tue Apr 22, 2008 4:57 pm Etc/GMT-1+01:00

Percepts,
I think I understand what you told Keith all except the parallelism bit, Could you elaborate as to what it is and how I would recognise it.

Afraid I am a rank beginner at this LF and am as a sponge soaking up all the info I can, my problem seems to be as a sponge I also dribble a lot away. Please excuse my ignorance but I am have so much fun learning with a view camera.

Regards Paul.

percepts · Post by **percepts** » Tue Apr 22, 2008 5:25 pm Etc/GMT-1+01:00

By parallelism I mean the GG must not be tilted in any direction in relation to plane on the rear rear standard where the film holder rests. i.e. its depth must be consistent across its whole surface.

Keith Tapscott · Post by **Keith Tapscott** » Tue Apr 22, 2008 7:32 pm Etc/GMT-1+01:00

Film holders/DDS`s have been mentioned and one person that I spoke to said he couldn`t quite get sharp focus on his Technikarden 4x5 when using Toyo DDS`s but got perfectly good focusing with Fidelity DDS`s.
I try to keep any movements to a minimum if possible and I am using a Kodak Readyload holder if that is of any help.

Keith Tapscott · Post by **Keith Tapscott** » Sat Apr 26, 2008 9:59 pm Etc/GMT-1+01:00

This article which was pointed out to me by an APUGer, who has been very helpful to me (and lives locally), has pointed out this useful link.
http://www.largeformatphotography.info/holders.html

Keith Tapscott · Post by **Keith Tapscott** » Sun Apr 27, 2008 1:48 pm Etc/GMT-1+01:00

percepts wrote:By parallelism I mean the GG must not be tilted in any direction in relation to plane on the rear rear standard where the film holder rests. i.e. its depth must be consistent across its whole surface.

A member of the apug forum kindly measured the GG of my MPP for me which was 4.90mm. The Toyo DDS was 4.67, the Fidelity Elite was 4.80 and each of the DDS`s had a sheet of film in the holder. The Kodak Readyload holder with a sheet of film was 4.87 and the closest to the GG.

Error on my part when focusing might be the problem as I couldn`t remember if I refocused after applying a bit of forward lens tilt or not, so I will take some more photographs soon when I have a bit of time to spare.

percepts · Post by **percepts** » Sun Apr 27, 2008 7:47 pm Etc/GMT-1+01:00

have a look at this page, and view all the movies so you get an idea of what is happening when you apply each type of movement.

http://www.trenholm.org/hmmerk/HMbook18.html

Keith Tapscott · Post by **Keith Tapscott** » Sun Apr 27, 2008 9:15 pm Etc/GMT-1+01:00

This might also be of interest.

http://www.youtube.com/watch?v=gR4m70xr ... re=related

du a gwyn · Post by **du a gwyn** » Sun Apr 27, 2008 11:12 pm Etc/GMT-1+01:00

Keith,thanks for pointing us to the video,what a great video it going to be a lot of help to me.he made it look so simple.off now to find a kellogs box!!
diolch yn fawr.