First shots with the Crown Graphic and 6x9 back - Focus problems?

[kuzano]

The two images of the GG back that you show ARE showing the back (or inside side) of the holder as being UP. I now look at the chrome hooks on each side and see that they are the hooks that face toward the lens inside the camera. Sorry... my mistake... but all the casting areas threw me off until I looked at my extra GG back I have in my parts trove.

That being the case, and looking down on the surface of the glass, the dull side should be the side facing up or inside the camera. The rough surface is where focus takes place, not the shiny side. The Ground Glass is just that, it is ground to be the focus plane.

So, aside from my first error, we should be looking at the dull side, not the shiny side. It looks like your ground glass is in the holder backwards. Throwing the focus point off even the thickness of the ground glass will play hell with your focus, because when you take off the ground glass and mount the roll film holder, your focus is off by the thickness of the ground glass. That is significant and critical focus on the film cannot be obtained this way. If you calibrate the rangefinder to the ground glass with this improper reversal of the glass, the rangefinder will never be matched to the placement of the film.

Does that all make sense, now that I see my original error in viewing the GG back holder again?

In any event, if you get the rough, dull side of the glass pointed into the camera, The measurement of the glass to the mating surface of the camera, MUST be equal to the measurement of the mating surface of the roll film holder down to the film itself.

There, I hope that clarifies the confusion I probably caused in this.

As far as hanging in there to assist, I am certainly willing to do so until it all comes together.

I just looked at those images of the GG and the film holder again, and am pretty sure, I have this right. All my other points about creating a system whereby the film sits in exactly the same location as the displaced ground glass after focus, should give you good focus on the film, even after you calibrate the rangefinder to the properly positioned GG and switch to rangefinder use.

This measurement is tenable and should remain workable UNTIL you switch to another film holder. Always check new holders as you acquire them to the one that you made the original adjustments with, or get a dimension for the GG back offset and apply it to future holders.

If you ever get another 4X5, of any other manufacture, this is a common first checkout procedure. The closer the two dimension are to being identical, the better the focus. There is not much room for difference at this first point of getting registration of the focus distance identical.

If you still have any questions on this we can continue on either on this thread, or you are welcome to PM me. I have a spare Crown Graflock back frame and ground glass holder, and will dig it out and may include some pictures as demo. I do not currently have a roll film holder, but I have a lot of various DDS (two sheet Double Dark Slide holders) and a late Pro model Kodak Readyload holder to get sample measurements from.

Hang in there. The WOW you get when you start seeing properly focused sheets of film is way worth the trouble. The first really great sheet of film I shot was a lake in the high Cascade mountains, with a lot of green reeds in the foreground, the lake and a rocky mountain peak in the background. I remember my jaw hitting the floor when I saw the processed print on Fuji Velvia 50. It was the most amazing surprise I have ever had with film, and validated large format for me ever since.

Oh yes, and John, I am not frustrated with you. I remember every step of sorting this out myself years ago, with an old Crown Graphic bought used at Columbus Camera Group in Columbus Ohio. 1989, no instructions and no internet.

I am frustrate however that the internet also poses it's own problems with getting this information to you in an orderly manner, and at my own errors in looking at the images you posted.

You seem correct in that your ground glass may indeed need to be turned over putting the dull ground side toward inside the camera. That could surely explain those original images you posted.

LASTLY HERE, I PUT A CORRECTION NOTE AT THE TOP OF MY POST THAT WAS WRONG ABOUT THE FIRST TIME I LOOKED AT YOUR GG HOLDER IMAGES, AND NOW THINK THE GG IS SHINY SIDE IN... NOT FOCUS SIDE IN.