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Barlow lens on a stereo microscope - much difference between 0.5x and 0.7x ?
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SolderSucker:
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
helius:

--- Quote from: SolderSucker on December 17, 2018, 04:44:28 pm ---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 greater distance between the scope and the PCB but with sacrificing the magnification a little?

--- End quote ---
No, 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.
Conrad Hoffman:
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.
SolderSucker:

--- Quote from: helius on December 17, 2018, 04:48:16 pm ---
--- Quote from: SolderSucker on December 17, 2018, 04:44:28 pm ---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 greater distance between the scope and the PCB but with sacrificing the magnification a little?

--- End quote ---
No, 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.

--- End quote ---

Ahhh, 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 ?
SolderSucker:

--- Quote from: Conrad Hoffman on December 17, 2018, 04:55:02 pm ---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 stereo scopes unless the eyepiece holders can be adjusted.

--- End quote ---

Interesting 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.
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