View Full Version : Making a DOF calculator for Chamonix 045n1 cameras

5-Sep-2009, 11:29
Acknowledgement: basically I used the method described here (http://www.largeformatphotography.info/dofknob/) by By Masayoshi Hayashi. So this is not an invention by me at all, just some quick tricks to make it easier for Chamonix 045n1 users to DIY a DOF calculator specifically for their cameras.

I believe this calculator work for 045n1 only. The rationale will work for 057n1 as well, but the enlargement ratio when printing the DOF sheet will need to be modified. Please see also Masayoshi's page for details.


Basically you will need two Fuji 135 film cans (white plastic), a scissor, scotch tape and a laser printer to do this.

1. download the DOF sheet from here (http://farm3.static.flickr.com/2460/3890425046_9d0c63074a_o.gif).

2. Print it using your laser printer with a proper enlargement/shrink ratio so that the distance between the two f/45 marks equals to 70mm.

3. Cut one of the 135 film can to get a strip of white plastic. wrap it around the other can and use scotch tape to connect the strip to a ring. you will need to add a small piece of white plastic cut from the first can to make it a complete ring, as the diameter of this ring will be larger than that of the second can apparently. Make sure the ring rotate smoothly around the second film can.

4. put the second film can onto the focusing knob of 045n1 camera. you'll find that it fits the knob quite well with perfect tightness. Now put the ring onto the can and slide it towards the end.

5. Find a proper reference point on the camera near the focusing knob. Do your tilt/swing job. when done, precisely focusing to an item at one end of the DOF. rotate the ring (while keeping the knob fixed) so that the '0' mark is aligned to the reference point you prefer.

6. Focusing to an item at the other end of the DOF. Now read the f/ number that is aligned to the reference point. Let's assume it's f/32. This is the minimum f/number you'll need to include everything in the DOF. Now back focus the knob until the f/number two-stop wider is aligned to the DOF, f/11 in our case. the camera is now focused to the optimized point for capturing everything in the DOF at the given minimum f/ number earlier (f/32 in our case).

7. For very large enlargement (over 1:10, or >50in for final output size), keep the optimized focusing position, while close down the aperture from the minimum DOF to 1/2 to 1 stop further.

5-Sep-2009, 12:21
A great idea ! Thanks !

The scale would depend on the ratio/pitch of the thread of the bolt used.
This Philips (Chamonix/Shen Hao PTB) design has so many posibilities for alterations and adaptations, in this way it realy has become camera's that can be changed to the photographer's wishes.


5-Sep-2009, 13:31
You're welcome, Peter!

As you have noted, the scale depends on the pitch. It also depends on the image format, final output size and viewing distance of the final viewer. For 045n1, the distance between two f/45 marks is 70mm, which in my experience is good till 1:10 enlargement (50in output from 4x5 sheet, 25cm viewing distance). For 057n1 I believe the pitch is the same, but the format is different, and therefore the scale will still be different.

5-Sep-2009, 13:44
A small revision for step 4: "put the second film can onto the focusing knob of 045n1 camera. you'll find that it fits the knob quite well with perfect tightness. Now put the ring onto the can and slide it towards the end."

I forgot to mention that obviously you'll need to paste the printed DOF scale to the ring using scotch tape, after step 4...

5-Sep-2009, 14:58
I don't have a Chamonix, will be building a PTB54 from brazilian hardwood when I am back in Holland in 10 day's........
That building myself means that I can make as many modifications to the design as I want (sizes of the knobs and more).
I have more idea's and will be putting the building process in a blog for all interested to read.

All these great idea's will go into a file and I will see which ones I will incorporate in the final design......


younghoon Kil
8-Feb-2015, 03:39

Millimeter scale.
Printed on 3M Post-It note.