Measuring distance to subject: can mobile phone technology help?

[Polar Bear]

As many of you will know I am all but as blind as a bat.  The primary issue with my sight is no detail and that nothing is ever in focus.  I see is shape, colour, contrast and shadow. 

I have recently acquired a Bronica ETR Si 645 medium format camera and am currently experimenting.  The biggest issue that I am having is of course I cannot tell when something is in focus.  It's just how my sight is and it is a stark reminder of why I embraced autofocus so readily.  I am of course estimating distance at the moment and setting the lens up considering distance and depth of field to help a little.

However, technology might be able to assist me with this, I hope.  What I was wondering is, does anybody know of any apps (I am on Android) which will do a reasonable if not perfect job of measuring distance to subject please?  I have done some digging but without much luck.  Anybody here come across anything out there that might just do an adequate job please?

[Jurek]

I know its not a mobile, but would a laser measure be of any help with this?

[Polar Bear]

Hadn't thought of that.  Would one work outdoors over a range of upto 20 metres?

[Jurek]

Hadn't thought of that.  Would one work outdoors over a range of upto 20 metres?

Yes.
ETA - One issue you may have with it, if you are unable to see detail,  is not being able to see where the red dot is.

[Polar Bear]

Quite right.  That will be an issue.

[lissotriton]

There's a few phones with a laser measure built in. eg Cat S61. But not cheap.

Maybe a scope-style laser rangefinder would be easier to use? As you can see what it is pointing at, not just looking for a dot?

[Pickled Onion]

You say you can see contrast - does the ground glass screen have split prism? It's a circle in the middle and you aim it at a vertical line/edge at the distance you want to focus to and it will be split when out of focus and line up when in focus. If this is within your eyesight's capability then it's very accurate and easy. If the screen on your camera doesn't have one, it's not too expensive to swap out.

Other things to consider: stopping down and setting the focus ring so the end of the depth of field is at infinity will give the near focus fairly close (depending on lens, and assuming it has DOF markings). Though you are more likely to need a tripod.  Using a wider lens gives much more depth of field and more latitude to not be spot-on. This is even true if you crop the image because you didn't want such a wide view. I don't know what lens you have, but if it's a long one it may be worth trading it for a shorter one, long lenses are much more critical to get in focus.

[Polar Bear]

Hi PO, split prism is worthless to me unfortunately.  Even when I could see better than I do now I gained no benefit from a split prism.  A plain screen is actually better given my particular sight issues.

Just one of those things ... 

[Polar Bear]

My stupidity knows no bounds.

We have a Sony Alpha 350 DSLR with autofocus.  It has a very nice Sigma 17-70 zoom which effectively covers the range of my two lenses and my aspirational third lens for the Bronica. (40, 75 and searching for a 100 or 105).

So, set the iso on the DSLR to what film I am using, set the lens zoom to correspond with the lens that I have fitted to the Bronica, point, press to get focus and readings then read off what the lens says for distance and the screen says for shutter and aperture adjusting to my preferences.

Just can't figure out why I didn't think of it before.

I can also take the shot with the Sony and compare the Bronica results with those from the Sony.

[Wombat]

Ah, excellent thinking!  Hopefully the distance is visible enough on the autofocus lens, to be useful to you?  My Zeiss prime lenses for my Sony A7Rii have got a fancy OLED display with exact distance displayed, but that s really a bit OTT, especially as I never look at it!