focussing with bifocal (trifocals)

[Ken C]

I wear trifocals and am having trouble focussing under the darkcloth. Should I be looking through the 'far' part of my glasses or the 'near'? Looking through the 'near' requires that I tilt my head back pretty severely and seems to be optimized for about 12" distance, anyway. When I'm focussing I'm usually closer (say 4"-8").

What about when I'm looking through my loupe? Which part of my glasses should I be looking through?

[Bruce Watson]

What I do to combat this situation is to use another pair of glasses. I took my camera in when I went to see my O. D. and showed him what I wanted (to focus about 5" away from the GG). This results in about a 2x magnification, and I can see the entire GG without moving my head. The prescription also takes my astigmatism into account, so what I see is spot on.

You can use a loupe like this too - IIRC magnifications add, so if you have glasses that give you 2x, and a 5x loupe, you get 7x.

This, and a Maxwell screen, works really well for me. Of course, YMMV.

[David Karp]

Ken,

Maybe Hogarth's way is the way to go. Maybe you could get a pair of trifocals that allow you to see distance and midrange for normal use while photographing, and a closeup lens that is optimized for working on the groundglass. That would probably work for most uses while photographing, because most of your "reading" (setting the f/stop, adjusting shutter speeds, reading mm scales, etc.) is usually done fairly close up.

I have progressive lenses and even the near portion does not allow me to focus the camera. The correction is not nearly enough for close work. I just take my glasses off and move my head until I can see the gridlines clearly, then focus. I adjusted my loupe so I can use it without my glasses, so it is not too bad. It is, however, a pain to keep taking my glasses off and putting them back on.

Other photographers have purchased magnifying glasses from the drug store, but I have not yet tried that. I can't bear the thought of taking off my glasses, replacing them with the magnifyers, focusing, and reversing the process.

Luckily, I did not really start lf photography until I needed the reading glasses, so I never got used to being able to focus with my glasses on.

[Joe Smigiel]

You might also try the clip-on/swing down diopters that jewelers use on their glasses. Googling should turn up many links and suppliers.

[John Cook]

I use an optician who owns his own one-man shop and is willing to indulge my fantasies.

He made me a pair of half-glasses which are so strong they look like coke bottle bottoms. For my correction, they focus at about eight inches. Also excellent for spotting prints and removing slivers.

For the camera ground glass he found and made up for me a gold-rimmed monocle, complete with neck cord.

Another popular setup is what he calls “plumber’s glasses”. They are bifocals with the close-focusing correction on the top instead of the bottom. They are apparently popular with plumbers who spend a lot of time sweating copper tubing fittings over their head between the cellar rafters.

If you get extra-strong reading glasses, you may be working too close to see the ground glass image from a Fresnel with both eyes at once.

Whenever I ask for something out of the ordinary, he has me bring in my camera and set it up in the front window for him to measure. The next project is going to be re-doing the 45-degree viewfinder to my correction.

[David Richhart]

I have had decent luck using a pair of drugstore glasses worn over my bifocals. They are inexpensive.

It's simple to try them out while in the store, standing at the display... but it is humbling to hear the young ladies giggling about the old guy wearing 2 pair of glasses.

[Christopher Condit]

I frame and do movements through the top of my bifocals, and take them off to use the loupe. It seems to me possible to focus the loupe by moving your eye closer/farther.

[Ralph Barker]

What would be really great would be a pair of plumbers glasses in which the lenses flip 180°.

The close segment of my bifocals are set fairly high and focus at about 6", which works pretty well under the darkcloth. Otherwise, I just take 'em off, and hang them from the neck of my shirt.

[David Bennett]

"A UK Optmetrists speaks...."

My first posting so bear with me..!

Ken, nice question you have lots of options,

1) Single vision specs optin=mised to the GG distance (take your camera to the OD practice0

2) "Plumbers specs" or "sign writers specs" - great idea!! Known as a "double D segment 28 (or 25) bifocal" in optom speak. this way you can specifiy the required powers in either segments and optimise them for whatever distance you prefer. The ideal solution.

3) with the loupe -whether you use the distance portioonon the specs or the near portion depends on the "exit vergance" of the magnifier. MOST and I stress MOST but not all have the exit vergance as the the light exits the magnifier parallel and so you use the DISTANCE portion of the lens. However if the exit vergance of the mag is negative then use the Near portion. Do a google search for your magnifier, ring the manufacturer and ask them for the exit vergance - you'll then be certain of the correct bit of your specs to use.

Hope that helps, I would (of course) advise you to see your optom. preferable a single owner practice - as they will take more interest ans care with you. Please tryto avoid the "heath robinson" solutions of off the peg specs- not a good idea although its the cheap (never a good thing imho - you pays ya money etc etc etc ) and you may end up in a right pickle!

with kind regards

David

[Bill Jefferson]

i WEAR bIFOCALS, BEST SOLUTION FOR ME IS A JEWELERS LOUPE, WHISH ATTACHES TO THE GLASSES AND IS 7X

[John Alexander Dow]

I got a special pair made, solely for use with LF, which sit in the same camera bag as the rest of the kit. They were prescribed so that I can focus at about 7 - 8 ins. Any nearer than that and the angle of view of each eye becomes too acute, particulaurly with fresnel screen, particularly with WA lenses. So I use a loupe if I want to get really close in the corners of the screen. But since most of my work is in the field, this usually is not necessary.

JD

[Rob Gertler]

Wow, judging from the number of replies, there must be quite a few of us geezers squinting and bobbing our heads under focusing cloths. I recently bought a $4 3x magnifier (from www.widgetsupply.com) that clips on the glasses frame and swivels so the magnifier can be positioned over the upper, middle, or lower trifocal lens, or out of the way when not in use. This works better than a loupe because it leaves both hands free. While this solution works well, I am mystified by the fact that some days it is easier to focus through the upper part of the trifocals, and on other days the lower or middle part seems to work better. Any ideas why this happens?

[David Karp]

Wow, great tips.

Thanks to Ken for starting the thread and all of the great suggestions.

[Ken C]

Hmmm... I need to remember to check back more often after asking a question <grin>.

Thanks, everyone, for your replies. I guess the consensus is that I should be looking through the 'near' part of my trifocals since many folks recommended some sort of magnifier. At least until I can get my optometrist to make me some focussing specs.

Thanks David Bennett, for the info re: "exit vergance", but, who's "heath robinson"? And by a "right pickle" do you mean I might damage my eyesight or just obtain some more out-of-focus photos?