Issue with 2x and 1x objectives

Everything relating to microscopy hardware: Objectives, eyepieces, lamps and more.
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AntoniScott
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Joined: Tue Dec 24, 2019 3:54 pm

Issue with 2x and 1x objectives

#1 Post by AntoniScott » Thu Nov 19, 2020 3:13 pm

I wanted to have an objective that gave me a lower magnification than 4x. I was able to buy an OMAX 2x objective but found that it had a large dark circle around the periphery severly limiting the field of view. I was hoping to get a 2x objective that gave me a wide field of view like I experience with my 4x objective. My microscope is an Olympus CH2.
Antoni

apochronaut
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Joined: Fri May 15, 2015 12:15 am

Re: Issue with 2x and 1x objectives

#2 Post by apochronaut » Thu Nov 19, 2020 5:39 pm

The lower the magnification the larger the actual field you are viewing. A 2X objective shows twice as much field as a 4X objective. That means the condenser needs to illuminate twice as much field. Standard microscope condensers usually only illuminate a field down to about 4X. Below that, there are usually aux. condenser lenses you need to add to your existing condenser to turn it into a wide field condenser. You leave it in place for the 2X and also can for the 4X normally and then remove it or swing it out of the way for the higher N.A. objectives. The aux. ccondenser lowers the condenser's N.A. as well as increasing it's field of view.
You can look up your condenser in the manual or on Alan Wood's Olympus site and see what aux. condenser it needs.

DonSchaeffer
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Re: Issue with 2x and 1x objectives

#3 Post by DonSchaeffer » Thu Nov 19, 2020 5:44 pm

Those low power objectives may best be illuminated like stereo microscopes with light from the top or side. Try mounting a strong flashlight.

PeteM
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Location: N. California

Re: Issue with 2x and 1x objectives

#4 Post by PeteM » Thu Nov 19, 2020 7:10 pm

Depending upon your microscope, that field limitation is likely due to the condenser not covering the entire field. Open up all the irises and drop it down to see if that helps. Some condensers will only cover a 10x objective, better ones will go down to 4x. As Phil says, it's often necessary to get a separate wide field condenser or a supplementary condenser lens to cover something like 2x.

Once you get to a 1x objective, it's rare to fine one that's parfocal in an older (or newer for that matter) microscope.

Kionka
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Joined: Mon Oct 26, 2020 4:53 pm

Re: Issue with 2x and 1x objectives

#5 Post by Kionka » Thu Nov 19, 2020 7:57 pm

If you plan to use only dry objective, consider getting the achromat swing out or better. I dont know if CH2 has the same dovetail condenser like BH2, but if it does, you can use the swing out achromat to light up the 2x. I am not sure about the 1x since they are rare and expensive, so others can speak better about this.

Greg Howald
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Re: Issue with 2x and 1x objectives

#6 Post by Greg Howald » Thu Nov 19, 2020 8:01 pm

I have a 2x objective. To use it I remove the condenser entirely. It will open the field of view and the condenser does little or nothing at 2x that you will notice. The condenser focusses light toward the center. With one or two x it seems that the light needs to spread out more. No science here. Just experience.
Greg

Chris Dee
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Re: Issue with 2x and 1x objectives

#7 Post by Chris Dee » Thu Nov 19, 2020 9:36 pm

I recently ran into this same problem. I bought a second Vickers M17 for the 1.25na achro' oil condenser and a second objective changer. The condenser is great but would not provide even full-field illumination for objectives below 6.3x and required swapping to to the original fip-top condenser for below 6.3x, not ideal (no aux' lens was made for this condenser). The 1.25na condenser has 3 filter trays, to get around this inconvenience I experimented with some lenses. One, a lens I'd saved from an old JVC camcorder worked well, so I printed a simple mount to fit one of the filter holders. The lens is concaved on one side and flat on the other. When swung in the condenser now works with objectives down to 2.5x. If you are unable to find a suitable condenser within your budget it could be worth your time experimenting with any lenses you have laying around and devise a mounting method if you enjoy tinkering.
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