Magnifying glass optics - glass questions...

[Scott --]

Hi, all -

An old article in View Camera has provided me inspiration, and some frustration today. Want to make a lens from a suitable magnifying glass, but finding the magnifier is proving difficult. Mark Sawyer found his, including a 14" FL one, at a dollar store. So, this morning, I packed the kids off to Dollar General, which, it turns out, isn't a dollar store. No joy there. Drive cross town to Five Below. Nothing. Stop at WalMart. They have one, but it's a bifocal one, and only 75mm FL. Try CVS, and while they have several, they're all bifocal as well.

So, I'm reduced to eBay. But I don't want to do this 20 times. So I ask, what should I be looking for? I've been told higher magnification equals shorter focal length. But I have no frame of reference on this. Is 5X to strong? What about coverage? Lens size?

Any help would be appreciated. I'm really excited about doing this, but am having trouble getting off the ground.

Scott

[BetterSense]

Why do you want magnifying glasses? You can buy any focal length or aperture lens double-convex lens that you want at Surplus Shed. Just use their Lens Finder. You can even get coated ones.

I bought a 3-pack of magnifying glasses--3 different sizes--at the counter impulse-buy section at my hardware store.

[Scott --]

I'll check Ace next time I'm there. As for why, (1) That's what was spec'd in the article, and (2) I had no idea about Suplus Shed, which looks wonderful.

So, the next question I have is what kind of lens do I want? Double convex? Positive meniscus? I dunno nada 'bout this... :eek:

Scott

[Scott --]

Oh my God. Surplus Shed is about 15 minutes from here... :eek:

[Peter K]

Positive meniscus?
With a positive meniscus, convex surface to the subject, you will get a Wollaston landscape lens often used also in millions of box-cameras. With such a lens you will get a much flatter field as with a biconvex lens.

To get the focal-length of a loupe in milimeters from the magnification divide it through 250mm. E. g. a loupe of a magnification 8x has a focal-lenght of 31,25 mm.

Have fun

Peter

[Daniel_Buck]

Oh my God. Surplus Shed is about 15 minutes from here... :eek:

lucky!!

[Mark Sawyer]

The front end off an old pair of binoculars might also work well:

http://www.largeformatphotography.info/forum/showthread.php?t=35482&highlight=pinkham

I've also had good results (at least by my own bottom-dwelling standards) using close-up diopters in various configurations:

http://i55.photobucket.com/albums/g139/Owen21k/L1020498-1.jpg

[Glenn Thoreson]

I save elements from junk lenses for stuff like this. I have one made from the front element out of an old Sears Super 8 movie camera that shows some real promise. I just glue the glass onto a lens board and stick it on a Speed Graphic. It needs the high shutter speeds when it's something like f/3.8 or so. :D

[erie patsellis]

Scott, whatever you do, resist the temptation to stop by and "browse". Such enterprises make it hard to say no to so many "treasures" you will find. (the voice of experience...)

[Scott --]

Unfortunately (fortunately?) I have no junkers from which to harvest optics. So, Surplus Shed is it. And, fortunately (unfortunately?) I'm not going to be able to go to Surplus Shed this week, so for now, I think I'm going to place an order for a few different lengths and designs. Have a machinist friend - seeing if he can turn me a barrel, barring the PVC route... ;)

[Bob Salomon]

Maybe you want to look at the Kaiser web site and check out their 2368 and 2369 magnifiers. http://www.kaiser-fototechnik.de/en/produkte/2_2_produktsuche.asp

[Jim Graves]

I was also impressed by Mark's work ... he was gracious enough to give me one of the Magnifying Glass sets he used in the photos in the article in View Camera Magazine. The magnifying glass purchase (for $0.99) actually contained two magnifying glasses ... the smaller covers 4x5, the larger 5x7. Here is an image of the two ... the smaller is mounted in a 4x5 Graflex board for use on my Speed Graphic ... the larger I have not yet adapted for photography:

http://home.comcast.net/~mary.j.graves/Mag%20Glass.jpg

The lenses are just double convex standard cheap lenses ... they are mounted in a plastic holder. I just sawed off the handle, filed a Graphic lens board to the right size and glued the lens and plastic holder in ... simple.

Here is an example taken with the lens on my Speed Graphic ... light was natural, film was Acros 100 QuickLoad:

http://home.comcast.net/~mary.j.graves/Willwebcopy.jpg

[Steve M Hostetter]

Any Office supply store: Office Depot
Office Max
Best buy
Fry's Electronic's
School supplies at Target
Michael's crafts

small ones are wide angles and the larger the diam the longer the focal length.. Buy em all