Help with focusing

[Matt5791]

I've bee dabbling for about a year with 5X7 LF since I bought an old Agfa Ansco. I'v eprobably only managed to shoot about 40 sheets so far, but I am not understanding what I'm doing wrong with focusing. I've read Ansel Adams book "The Camera" and the chapter on camera movements, but still dont really understand what I might be doing wrong, apart from I obviously have either a depth of field or depth of focus problem.

Basically I am getting focussing errors at the top and bottom of the negative, sometimes - have a look at the attachment - I'm pretty happy with the exposure and development here (apart from the stain - don't know where that came from!) (this is a straight scan from the negative) but the top of the spire of the church and the base also, is well out of focus, but razor sharp in the middle section.

The lens is a SA 120mm f8. It was set to f45 or f32 fo the exposure (can't remember exactly) Film is Adox CHS100.

Would be grateful for any help - maybe I'm trying to be too clever using camera movements at this stage?

Thanks
Matt

 

[Ian Grant]

Hi Matt, you definitely need to use front/rear tilt. I'm not sure if your Agfa Ansco has front tilt, and the rear tilt isn't very much, certainly not enough for the image attached. If you can get enough tilt this is a simple image to set up on the screen.

The stain looks like a contamination mark, perhaps a splash of stopbath or fix, it's certainly chemical.

Ian

 

[David H. Bebbington]

Think of it this way - the bottom of the tower (appearing at the top of the screen) is closer to the camera than the top, so the screen needs to be (a little) further away to get it sharp. I would think your Ansco would have enough backwards tilt to achieve this, it would only be a degree or two. It may be that your camera bellows are too compressed to allow any camera movement, it may be that you are applying the correct amount of tilt and the bellows are "cancelling" this by pushing the screen straight again. A Super Angulon lens should give more than enough coverage to allow top-to-bottom sharpness with either front or back tilt.

Regards,

David

 

[Neanderman]

Would be grateful for any help - maybe I'm trying to be too clever using camera movements at this stage?

It's never too early to learn how to use camera movements. That's half of the reason for using a view camera (the other being the film size.)

Movements are not nearly as complicated as reading about them seems. Two simple rules to remember:

• Tilting or swinging the lens adjusts your planes of focus.
• Tilting or swinging the back adjusts convergence.

See if this helps: http://www.trenholm.org/hmmerk/SHSPAT.pdf Focus on looking at the drawings rather than the text. Scheimpflug is best explained visually.

Ed