A couple o large format questions

[Bob F.]

A 150mm lens at f/11 focussed at 4m gives sharpness from about 3.4m to 5m (less if you want a big enlargement or are more critical ): quite shallow but enough to allow some movement.

I use this program (http://www.dofmaster.com/custom.html) to make 2.5" diameter calculators for each of my lenses.

Cheers, Bob.

[jnanian]

it sounds like you were not able to focus well-enough
with the dark cloth and ground glass alone. you'll get better as
you make more exposures ...

i use a toyo focus loupe on all my cameras.
it is the single lens that is attached to a big
rubber thing. it snaps onto the back of a toyo camera
( i think they call it a monocular focusing loupe ? )
i just stick it against the ground glass of whatever i am using,
and find it works pretty well. i think i paid 15$ on ebOO a few years ago.

i have never heard of anyone making portraits stopped down to f64 or f90,
maybe a grand landscape like "siransel" used to make ...
or if you are using a mamouth plate or ulf camera, where f64 or 90 is kind of like
stopping down to f16 or 22 in a smaller format like 4x5 ... your f16 or 22 is fine.

good luck!

[raucousimages]

I like my Toyo loupe. The small Dia. lets it get into the corners of the glass tighter than my Rodenstock. When the kids come with me my son uses one of those 10X loupes for viewing 35mm slides. A bit high power but it works.

[Frank Szabo]

It could be that your subject moved forward slightly between focussing and shooting? it may not be your fault as regards D.O.F.

That is one reason I'll not use a large format camera very often on people except at a distance; they fidget, move around, and do all manner of things my non-autofocus Sinar can keep up with.

That's what the RBs and Hassies are for.

[ic-racer]

You may well have focused perfectly. In my experience a standing human will not appear sharp on film at 1/2 second and can appear out of focus. Use a faster shutter speed and open up the lens. For a portrait, the center of the lens field should be OK at wider apertures. Usually the face and body parts don't extend to the edges of the frame, so its OK to forgo sharpness there. Of course when you open up you need that metal 'C-collar' to hold your subjects head in place while you put the film holder in place . Frank makes some good points.

[Jarvman]

One other thing I've discovered. The clock in the picture behind him looks slightly distorted as a result of lateral shift. I read in the large format book I got given that shifting the lens will alter perspective wheras shifting the rear standard will only slide the image across the ground glass. Is there a way of applying shift to the rear of a chamonix? There doesn't seem to be an easy option but I'll have a look now.

[nemo999]

One other thing I've discovered. The clock in the picture behind him looks slightly distorted as a result of lateral shift. I read in the large format book I got given that shifting the lens will alter perspective wheras shifting the rear standard will only slide the image across the ground glass. Is there a way of applying shift to the rear of a chamonix? There doesn't seem to be an easy option but I'll have a look now.

Shifting the lens (pushing it from side to side or up and down while keeping it parallel to the film) will not change perspective and has the same effect whether you shift the front or rear standards - it is limited by lens coverage. Past the limit of lens coverage, vignetting will occur. With swing and tilt movements, there is a world of difference between front and rear. Front swing and tilt will never change perspective, but you will soon run out of lens coverage (quicker of course with a wide-angle lens than with a long focus). With rear swing and tilt, you will never run out of lens coverage, but you will elongate the image in proportion to the amount you move away from having the film plane parallel to the front standard.

[Shangheye]

A key difference here is between "distortion"and "perspective". Rear standrad tilt will alter the PROPORTION of the relative areas of the image tilted towards and away from the film plane. However front standard tilt does not alter this Proportion as much, but definitely does cause distortion towards the edges of the frame....generally a circular object will look more elliptical. If you trawl the internet, you will find many papers written on the effect. Shifting the lens (moving it sideways and parallel to the film plane) has NO impact on distortion, only on the portion of the lens image falling on the film. I am assuming you mean you tilted the front standard, and if so, I am not surprised you got a slight distortion...especially with a 150mm lens. Back standrad tilt would not casue this distortion I believe (I don't have back tilt on my camera so can not be sure) but would change the proportions in the image between foreground and background...or "Perspective"as Nemo states above.

Rgds, kal

[Jarvman]

Nah, I shifted it left keeping both standards square. I must've misread the book somehow, it's probably the way the clock is hanging off the wall. If you say lateral shift causes no distortion I'll believe you.

[Bob F.]

If you think about it, shifting the lens panel 2 inches left is the same as moving the camera 2 inches to the left and shifting the rear 2 inches right: the panels end up in the same locations. So, a front movement can be emulated on the back standard by thinking about where the two standards end up. This applies to other movements you might want but do not have them available on the back standard; rear upwards tilt for example can be had by tilting the whole camera up and shifting the lens panel down and tilting it forward so it is now vertical (use your hands as the standards to visualize it).

There is a difference between shifting the front or rear (assuming the tripod stays where it is). Shifting the front causes the near/far relationships to change - it's like taking a step to the side to peek around a post to see what is behind it. Shifting the rear only causes the image to move across the ground glass - it does not effect the relationships of objects. In both cases, as said, there is no additional distortion (except any added by the lens now you have perhaps moved closer to the edge of its image circle).

Cheers, Bob.