100X Semi Plan DRY Objective - NEVER use oil again

100x Dry Objective – no need for oil?

If you work with 1000x magnification, you’ll be familiar with the annoyance of oil immersion microscopy – the constant cleaning of lenses, stages, slides and your fingers.

For many people, those days may be over.

In the past few years, 100x dry lenses have become available. These lenses aim to reduce the need for immersion oil by providing a dry image that claims to be 95% as sharp as an oil-based image.

100x Semi Plan Dry Microscope Objective Lens


There are a few obvious advantages to a dry 100x lens.

Speed and efficiency

The main advantage is efficiency. If you don’t have to prepare slides with oil or to clean your equipment after use, you’ll save a lot of time that can be spent more productively.

You’ll be able to swap slides much faster too, allowing you to get faster results.


When you’re working without oil, there’s no longer a risk of oil-related damage, always a hazard if your equipment is improperly cleaned or maintained.

It’s also common for people to accidentally dunk their 40x non-oil lens into the immersion oil, which can cause lasting harm and require professional servicing.

So dry lenses can help keep repair and replacement costs to a minimum.

Save $$ on oil

It’s obvious, but you won’t need to buy immersion oil. Over time, this could be a cost-effective option.


There are some downsides to dry 100x objectives too.

Lower resolution

The most important consideration is the lower resolution of dry lenses.

They have a lower numerical aperture value (NA) than their oil-based equivalents, with a maximum NA of 0.95.

NA is a measure of the ability of a lens to resolve fine detail – lower values mean a lens is less capable of seeing detail at higher magnifications. Essentially, it’s the resolution of the lens.

When working at higher magnifications, such as 1000x, resolution is important. If your lens doesn’t have enough resolution, your image will be blurry and distorted.

As a rule of thumb, the NA of a lens multiplied by 1000 gives you the maximum magnification of that lens, beyond which you’ll get lower visual quality.

100x dry lenses often have an NA of 0.85, which means their image quality starts to degrade beyond 850x magnification. At 1000x magnification, the image is not as clear and detailed as it could be.

Oil lenses with an NA of 1 or above would have the resolution to see the detail in that last 150x magnification.

The image quality of a dry lens is still good, but not as good as it could be. Whether that’s an issue comes down to your circumstances and preferences.


100x dry lenses are not cheap right now. Lower end lenses can be $400 to $800, while high-end lenses can cost thousands. Prices could come down over time, but for now they might be out of the reach of casual users.


There’s no substitute for the resolution of an oil lens. If image quality is paramount, you shouldn’t consider a 100x dry lens.

However, if your purpose allows for lower quality images, dry lenses could save you a lot of time and mess. The potential productivity gains are huge, and you can say goodbye to the ever-present worry of oil damage.


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