Depth of Field Chart for 6x17

[Travis]

Hi everyone,

Just wondering if anyone knows which depth of field chart I should be using for my particular setup. I'm using a 4x5 camera, but with the Shen-Hao 6x17 back. Do I go by the 4x5 chart? Or would it be better to go by the 5x7 chart, as that is closer to my image size?

Thanks,
Travis.

[Eric Jones]

Travis,

Unfortunately I can not answer your question but I am curious about your thoughts on the Shen-Hao back and what lenses you are using with it.

Thanks

Eric Jones

[Leonard Evens]

Depth of field calculations depend on an assumed value for the circle of confusion. That in turn depends on the degree of enlargement you expect for your final images and how they will be viewed. But because the aspect ratio is so different from other formats, it is hard to predict what a reasonable degree of enlargement would be. One could argue that, in terms of degree of enlargement, 6 x 17 is closer to 6 x 9 than to 4 x 5. So I would use tables designed for 6 x 9 to start. If these overestimate how far you have to stop down for desired dof, just open up a half stop or so more than the tables suggest.

Keep in mind also that even for standard formats like 6 x 9 and 4 x 5, different people will disagree about what a reasonable choice of coc is. I generally use 0.1 mm for 4 x 5 format, but many people would use smaller values, as little as 0.05 mm for the same format. Every dof table is based on some assumption about the dof, and that assumption may not be valid for the kind of work you do.

[Leonard Evens]

"Every dof table is based on some assumption about the dof, and that assumption may not be valid for the kind of work you do.
Sorry. it should be "some assumption about the coc".

[Ralph Barker]

I would think that DOF calculations for 4x5 would be conservative for 6x17, while those for 5x7 would be closer, but a bit loose.

The DOF calculator on my site is written in straight HTML, and while copyrighted by the original author and restricted from commercial use, can be easily modified for other formats or other assumptions for the various CoC values (if one is reasonably script-savvy). Just do a "view page source" within your browser, and cut/paste the code to your own HTML file to play with it.

[Stpephen Willlard]

There is a very effect simple method for determining DOF. All you need is a small ruler in mm and a simple chart.
It works independent of lens, format, COC, and camera movements. I have been using it for about a year now and it
has worked everytime without exception.

The method is detailed right on this website at www.largeformatphotography.info/fstop.html.