Which Achromat 5x loupe

lothman · Post by **lothman** » Thu Aug 24, 2017 7:35 am

zzffnn wrote:
lothman wrote:go for a slide projector lens, for example a Leica colorplan 90mm. Will give you more than a 4x loupe but has excellent sharpness even to the extreme corners, best color, no distortion, good working distance and a robust housing.
Thank you! So what visual magnification does that lens provide? Sorry, my optical math is terrible. That particular Leica lens seems to sell for over $50 USD and slightly out of my budget for this application though.

Here in my office I use a Leica Hektor 1:2,5/85mm slide projector lens (3$ flea market ;-) ).

If I use it direct near my eye (similar a watchmakers loupe) I have a field of view of ø5cm, if I use it at distance held by hand I get a FOV of ø1,5cm kind of vignetting. But I can move my head and look around in the lens in my hand and the can see the same 5cm FOV.

Slideprojector lenses do not have an aperture (not needed when using as loupe), are better to hold and have a bigger diameter than enlarger lenses. So I recommend them over a enlarger lenses. You don't have to go for Leica any brand will be OK. Look for an aperture 2.8 or bigger, those usually were the best versions available and those are also suited best as a magnification loupe because the big diameter makes it easier to look through. In the worst case you have to buy an old slide projector and unsrew the lens .

Edit:
http://www.surplusshed.com/pages/item/l10536.html

zzffnn · Post by **zzffnn** » Thu Aug 24, 2017 11:54 am

Thank you very much, gents.

How is LOMO RO-109 projector lens 50mm F1.2 for my purpose:
http://www.ebay.com/itm/16KP-1-2-50-50m ... 1935147573

I noticed it is quote long and may be heavy too?

Konica 40mm F1.8 is not cheap on eBay currently. ChrisR, what is the clear lens diameters of your version?

I am guessing clear lens diameter, especially the objective side, correlates with FOV.

I did a more careful experiment and did notice that FOV changes when eye-lens distance changes (as lothman kindly pointed out). So my Schneider Componon S 50mm F2.8 offers FOV of around 20mm max, which is slightly less than what I want, though it is otherwise perfect.

I do like more FOV, because I wear strong eyeglasses (even though I could remove them) and my kids could use wider view too.

For my shells, 5x visual is definitely better than 10x. Light gathering and depth is too limited with 10x loupe (I bought it for small ants, which is a good fit at 10x).

I would like to stick to around 4x-6x visual magnification. So 80-90mm FL may not he powerful enough?

neurodoc · Post by **neurodoc** » Thu Aug 24, 2017 12:54 pm

When I was taking botany and geology courses in college I used Bausch & Lomb Hastings Triplets. They came in 7x and 10x, as well as higher magnifications. They give good images, are quite handy, and tough...I still have mine from the old days. I'm pretty sure they still make them.

zzffnn · Post by **zzffnn** » Thu Aug 24, 2017 1:03 pm

neurodoc wrote:When I was taking botany and geology courses in college I used Bausch & Lomb Hastings Triplets. They came in 7x and 10x, as well as higher magnifications. They give good images, are quite handy, and tough...I still have mine from the old days. I'm pretty sure they still make them.

Thank you, I am aware of 7x B&L Hastings triplets. I need close to 4x and 5x though and I already have a 10x achromat loupe. So not a 7x this time.

ChrisR · Post by **ChrisR** » Thu Aug 24, 2017 1:50 pm

Konica 40mm F1.8 is not cheap on eBay currently. ChrisR, what is the clear lens diameters of your version?

Prices on ebay seem to follow an exponential decay, plus "what it's actually worth". Today $100, wait a week, $50, wait a month, $40...

I'll try to find it, but it may take a while.

A standard Nikkor 50mm f/1.8 gives me a 40mm fov (not reversed); much wider than the hole. It's more comfortable reversed, but then 28mm dia.

A very usable, powerful magnifier I have is a 20x Unitron ELWD objective. It was cheap. CA is an issue on a camera, but eyeballing, I don't notice it.

zzffnn · Post by **zzffnn** » Thu Aug 24, 2017 9:50 pm

zzffnn · Post by **zzffnn** » Sat Sep 16, 2017 3:17 pm

So I bought a Peak 4x anastigmatic loupe for a good price:

http://www.peakoptics.com/index.php?mai ... ucts_id=13

The problem is its working distance is too short. When focused onto a flat paper, its bottom lens is about 16mm away from the paper, which is too short for my application. In comparison, my Peak 10x achromat loupe has working distance of around 20mm.

I think my definition of working distance is very different than manufacturer's definition. Because "working distance", as shown in their web page, is 54mm.

This is my Peak 10x achromat loupe (there is no manufacturer's working distance for it, though I measured it to be around 20mm, o'er my own definition): http://www.peakoptics.com/index.php?mai ... ucts_id=12

Does anyone know how loupe working distance is defined by Peak?

I will have to sell the loupe. Not only its working distance is short, it is also too huge (56mm wide bottom lens, 264 gram weight) for portable use. There the manufacturer's specification is actually correct, but I failed to notice it

Optical correction of the 4x loupe is very good, with very wide view field.

My Schneider Componon 50mm F2.8 actually has much longer working distance.

zzffnn · Post by **zzffnn** » Mon Sep 18, 2017 2:59 pm

Just bought a Canon FD 50mm F/1.4 to use as home 5x loupe, when I don't want to use stereo scopes. Will use a cheap single lens 5x loupe in the field, as the Canon is not small or light. The Canon has woring distance of about 29 mm.

The FD lens will also be used for portrait / bokeh, on my micro four thirds camera, via FD to m4/3 adapter.

Will the FD 50mm F/1.4 get close to my Schneider Componon S 50mm F/2.8 as macro lens, when reversed and/or extended? I read that its normal close focus is 0.45m. People also said it is quite sharp, when stopped down to F2.8 or so.

zzffnn · Post by **zzffnn** » Thu Nov 16, 2017 5:27 pm

So I bought this Surplus Shed 5x achromat loupe http://www.surplusshed.com/pages/item/l3107.html

and compared it to the Canon FD 50mm /F/1.4 lens used in reverse.

I prefer the 5x loupe, as it offers around 40mm field of view and 45mm of working distance (as measured from bottom lens to flat paper).

The Canon lens offer around 26mm FOV and 30mm of WD, with very slightly better image quality.

The Surplus Shed loupe came to me with some semi-transparent white film near the outer 30% though. And those are located in between glued lens elements.

Maybe minor delamination or mold? They do not seem to affect image quality significantly, but the lens probably won't perform at 100% either. They don't look like water vapor based on their looks, also shipping came slowly from north to southern USA and temperature changed very gradually (so water vapor should not form). Just a warning for future buyers. I won't bother to return or ask for refund, though I have contacted Surplus Shed to warn them about the white film (which may be on their remaining 5x loupes).