Focus distance
Focus distance
I have a 90x zoom stereo but sometimes want more mag. It has 10x wf eye peices. What options do I have? I need to allow for not being able to get the lens closer than 15mm to the subject. Can i replace the eye prices with 20x or 30x? If I get a compound scope, can I run 10x objective with 30x eyes okay? I have a 2x 48mm barlow lens to get it to 90x. Can i use a 3.5x barlow lens? I find focus difficult with a 2x as it is. I mainly use it to view minetals. I plan to fit a 13mP camera so with the 2xbar,ow, might get enough digital zoom? I am thinking equivalent to about 300x optical. Any thoughts welcome.
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Scarodactyl
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- Joined: Sat Mar 03, 2018 9:09 pm
Re: Focus distance
20x is about the reasonable limit on eyepieces, though higher do exist.
You are unlikely to find an aux lens above 2x, and even with high end systems with whole interchangeable objectives going over 2x is uncommon. At some point the short working distance makes it impractical.
Either way, a stereo system is not ideal for this. There are inherent limits to the resolution of a stereo even before you take the long working distance into account. It is very likely you will butt up against some resolution issues if you try to push that 9x optical up to 30x.
You'll get much better results with a higher resolution compound objective. Long working distance optics can get pricey but 15mm isn't an insanely long wd, and there are 20x objectives with longer wd than that.
You are unlikely to find an aux lens above 2x, and even with high end systems with whole interchangeable objectives going over 2x is uncommon. At some point the short working distance makes it impractical.
Either way, a stereo system is not ideal for this. There are inherent limits to the resolution of a stereo even before you take the long working distance into account. It is very likely you will butt up against some resolution issues if you try to push that 9x optical up to 30x.
You'll get much better results with a higher resolution compound objective. Long working distance optics can get pricey but 15mm isn't an insanely long wd, and there are 20x objectives with longer wd than that.
Re: Focus distance
Thanks once again. I am learning a lot I can't find elsewhere. Much appreciated. I was thinking compound would be the go but was concerned with the working distance. Sometimes I look into small cavities. Ill check out your suggestion for long wd objectives.
Re: Focus distance
You can buy long and extra long working distance objectives. It is typically best to use about 10x eyepieces and put the magnification in the objective. So, with a 10x and a 20x LWD (long working distance) objective you'd have 100x and 200x (and so on for higher powers).
Note that while the working distance will be longer than usual, as you get higher magnifications you will have less and less depth of sharp focus.
What are you trying to image? That can help us suggest a good alternative.
Note that while the working distance will be longer than usual, as you get higher magnifications you will have less and less depth of sharp focus.
What are you trying to image? That can help us suggest a good alternative.
Re: Focus distance
I want to view micro minerals. As they are often in cavities, I need a longer WD than a standard compound set up. I saw some attractive objectives online but I don't have 5 k to spare. I use the stereo to locate subjects but want higher mag to view well. I was hoping to image as well using focus stacking.
Re: Focus distance
An affordable option might be a used industrial microscope of the sort used for wafer inspection -- with "epi" or through the lens illumination from above. Be sure it has objectives marked "LWD" or "ELWD" or equivalent for long working distance and extra long working distance. There are often marked with the actual working distance.
The higher the power you go, the less working distance (even with LWD objectives) and the more difficulty you will have in getting sufficient supplemental illumination. But at least with focus stacking you will be able to get a sharp final picture despite the shallow depth of field.
Even if you added a supplemental lens to a stereo microscope, a compound microscope is likely to be the more ergonomic and stable platform for focus stacking.
The higher the power you go, the less working distance (even with LWD objectives) and the more difficulty you will have in getting sufficient supplemental illumination. But at least with focus stacking you will be able to get a sharp final picture despite the shallow depth of field.
Even if you added a supplemental lens to a stereo microscope, a compound microscope is likely to be the more ergonomic and stable platform for focus stacking.