# 60X and different tube lens config for malaria detection? **URL:** \ **Category:** General\ **Created:** [20 August 2025 11:59 UTC](https://openflexure.discourse.group/t/60x-and-different-tube-lens-config-for-malaria-detection/2237 "2025-08-20T11:59:11Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![amchagas](https://avatars.discourse-cdn.com/v4/letter/a/8491ac/32.png) [@amchagas](https://openflexure.discourse.group/u/amchagas)\ **Post date:** [20 August 2025 11:59 UTC](https://openflexure.discourse.group/t/60x-and-different-tube-lens-config-for-malaria-detection/2237/1 "2025-08-20T11:59:11Z")
Hi OpenFlexurers! This probably has an easy answer, but I couln’t find it, so here pestering this community… I am rewritting this question with a more informative title From what I understand, if we change the tube lens on the microscope, or even remove it completely you can change the magnification of the scope, or in other words what area of you sample covers the area of the camera sensor. (a lot of this understanding comes from the OF documents themselves [Assembly Instructions](https://build.openflexure.org/openflexure-microscope/v7.0.0-beta1/info_pages/imaging_optics_explanation.html) ) So my question: For malaria imaging, why not change the configuration of the optics in a way that an 100X oil objective is not needed, but rather something like a 60X air? As in adjust tube lens parameters in a way that using the 60X you can get the same area of the sample covering the same area of the camera sensor as compared to the 100X? If this is something feasible, it would remove the need for oil, decrease costs slightly (as 60X are a little cheaper than 100X) and things would be more forgiving in terms of focusing/adjusting things? ---
**Author:** ![WilliamW](https://yyz2.discourse-cdn.com/free1/user_avatar/openflexure.discourse.group/williamw/32/106_2.png) [@WilliamW](https://openflexure.discourse.group/u/WilliamW)\ **Post date:** [20 August 2025 17:43 UTC](https://openflexure.discourse.group/t/60x-and-different-tube-lens-config-for-malaria-detection/2237/2 "2025-08-20T17:43:26Z")
There are two aspects to the size of a microscope image - magnification and resolution. This is explained in [Magnification, resolution, and field of view](https://gitlab.com/openflexure/openflexure-microscope/-/wikis/Magnification,%20resolution,%20and%20field%20of%20view), which is rather hidden in a wiki in the repository. You can make an image larger using a different tube lens, or simply by displaying it on a larger screen. I had OpenFlexure images on a screen that was probably 10m across at a recent conference. Doing this will not increase the amount of detail in the image. The detail in the image is determined by the smallest thing that can be seen distinctly from its neighbours. This is the resolution, which is determined mainly by the objective lens. The numerical aperture is the important property of the objective in determining resolution. It is possible to have 100x lenses that do not give better resolution than 60x, because they are not designed with high NA. Usually higher magnification objective lenses in a series have higher NA and higher resolution. ---
**Author:** ![r.w.bowman](https://yyz2.discourse-cdn.com/free1/user_avatar/openflexure.discourse.group/r.w.bowman/32/15_2.png) [@r.w.bowman](https://openflexure.discourse.group/u/r.w.bowman)\ **Post date:** [21 August 2025 11:12 UTC](https://openflexure.discourse.group/t/60x-and-different-tube-lens-config-for-malaria-detection/2237/3 "2025-08-21T11:12:39Z")
In principle you can do that - to be honest I’m not really sure you’d need to change the tube lens as, as William says, the magnification’s not that important. A really good 60x might get close to the resolution of a 100x, but it will never capture as much detail as a 100x oil lens. It will also usually be more expensive. I have generally been very conservative: the WHO guidance says you need a 100x oil lens with an NA of 1.25. The important part of that specification is the NA=1.25, which is ultimately what determines resolution. An NA greater than 1 is not physically possible with an air objective, so while it’s possible to match the magnification, it will not get the resolution required. A 60x oil immersion objective with an NA of 1.25 would work beautifully. However, those are expensive beasts! Whether that resolution is actually needed is a debate worth having. However, I think it’s a tricky thing to get right, and I have always felt more confident knowing that the optical system follows the WHO’s guidance for malaria.