Barlow lens on a stereo microscope - much difference between 0.5x and 0.7x ? - Page 1
Forum section: electronics / projects

author: SolderSucker
author_rank: Regular Contributor
timestamp: December 17, 2018, 04:44:28 pm
content: Just bought myself an AmScope with a 0.5x Barlow lens - I'm wondering if there is much difference between a 0.5x and 0.7x Barlow lens.Will a 0.7x allow me even greater distance between the scope and the PCB but with sacrificing the magnification a little?I'm wondering if the difference will be noticeable enough to warrant the expense. What is the extra distance likely to be if using a 0.7x (are we talking only 25mm or so) and how much less magnification?I've been hunting around but can't find anything showing a good enough comparison.Thanks

author: helius
author_rank: Super Contributor
timestamp: December 17, 2018, 04:48:16 pm
content: Quote from: SolderSucker on December 17, 2018, 04:44:28 pmNo, it's the other way around. A 0.7x barlow has less working distance, and less decrease of magnification.The lens powers in an optical system are multiplied together to reach the final magnification. So a 4x objective with a 20x eyepiece means 80x magnification. The fractional power of a barlow lens means that it reduces magnification when added to the microscope.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: December 17, 2018, 04:55:02 pm
content: I just pulled the barlow lenses off our microscope. They screw up the field of view and make it much harder to get a good stereo image. I can live with the closer working distance since the view is so much better. They also mess up parfocalality (is that a word) on the zoom stereo scopes unless the eyepiece holders can be adjusted.

author: SolderSucker
author_rank: Regular Contributor
timestamp: December 17, 2018, 05:00:13 pm
content: Quote from: helius on December 17, 2018, 04:48:16 pmAhhh, I see, thank you! I'll stick to the 0.5x then.Is the distance and magnification difference a relatively small amount between 0.5x and 0.7x ?

author: SolderSucker
author_rank: Regular Contributor
timestamp: December 17, 2018, 05:07:13 pm
content: Quote from: Conrad Hoffman on December 17, 2018, 04:55:02 pmInteresting you should mention that as at first I just couldn't adjust the eyepieces to get a good view - moving my head up, down, left, right was causing blackness to appear, or the image became a small spherical area, etc. I'm getting the hang of it now but I'm still not 100% happy with the image due to this, I guess I'll continue to get the hang of it. That's with the 0.5x Barlow on it - I may try taking it off to see what the difference is.Incidentally, if you're not using a Barlow which lens do you have on it? Just a 1.0x to protect the stereo lenses inside the scope? I understand that they can become permanently cloudy with solder and flux fumes after a period of time if they're not protected.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: December 17, 2018, 05:56:10 pm
content: It should have a plain window for protection, but somebody lost it, so I'll just clean it every now and then. If it gets too mucked up, we'll replace it. We use inexpensive Asian imports, but I'd love to have a Wild Heerbrugg.

author: Fred27
author_rank: Unknown
timestamp: December 17, 2018, 06:01:46 pm
content: When I bought mine I got a x0.5 and a x2 Barlow lens. Not for soldering obviously, but great for when the kids are looking a bugs, etc.

author: jfiresto
author_rank: Frequent Contributor
timestamp: December 18, 2018, 04:15:21 pm
content: Quote from: Conrad Hoffman on December 17, 2018, 04:55:02 pmThat is odd. Adding an 0.5X or 2X auxiliary lens to my microscopes, or removing one, does not disturb the stereo imaging or the parfocality: it only changes the field of view and the working distance. I wonder, is that "barlow" lens trying to do something that could or should be the job of the host microscope?

author: Stiletto
author_rank: Contributor
timestamp: January 11, 2019, 01:29:24 am
content: Quote from: SolderSucker on December 17, 2018, 05:07:13 pmPrecisely, I run with a 1x that has the scope ring machined into it, just to protect the scope's objectives on my SM-4NTP. The 1x lenses are way cheaper to replace than even an Asian scope!