Advantages and Disadvantages about Infinity tech

[P_Tadrous]

Hello @latot and welcome to the forum.
Firstly, I would say that for a person to chose a microscope the question of ‘infinity or not’ is not the most important criterion. The choice actually more importantly depends on your intended uses and your budget.
For most professional users in well-funded departments I would say that for most standard purposes it would be best to go with one of the major microscope manufacturers’ modern scope series - and these are ~always going to have infinity optics so that decision has been made for you. If you are in this group take a look at this post for more info:

Zeiss, Nikon, Olympus, Zeiss: How do you choose?

First and foremost is your intended use and imaging needs - both now and in the foreseeable future. If all of them have scopes that can do what you want, then move to the following points but bear in mind that they must have everything you need available now - don’t assume things will come in the future. So get that info from the reps. All those manufacturers have good customer support networks - so that box is ticked. Price - not just for the scope(s) but for ongoing support and servicing. Lo…

If you are a private individual wanting to do microscopy as a hobby or have a low budget then maybe a second hand older scope like a Leitz or Olympus BH2 series would be better but I would go with those that use a 160 mm mechanical tube length (so not the older Leitz with 170 mm objectives because they are the ‘odd ones out’).

If you are on a low budget - whether professional or amateur - and are happy to customise your scope and put a lot of time and effort to get exactly what you want to do in a creative way, take a look at my open source microscope, the PUMA system here:

GitHub - TadPath/PUMA: 3D Printed Microscope

and see some of the instructional videos on my YouTube channel here:

PUMA Microscope

As for your list of pros and cons of infinity optics, I would say your list of disadvantages is very good but would add some more:

• It is not just the threads that are brand-specific (some of them are actually cross-brand compatible) but the actual design of the tube lens and objective optics are brand specific which means that even if you find an objective from another manufacturer that fits the thread, the image won’t be so good because their objective will need to be corrected by their own brand of tube lens.

• The ‘infinity’ space does not actually go on for infinity in practice because although the ‘rays’ coming out of the objective are parallel, the image beam is not parallel but divergent. The more ‘add-ons’ you put in the infinity space the more image quality will be lost (because more of the divergent imaging beam will have hit the sides of the microscope tube and be lost to the tube lens - then of course there are diffraction effects). This effect is not really noticeable for just a few standard add ons so it not a huge problem but just be aware that you can’t keep adding modules and expect image quality to be unaffected. If this concept of diverging beam of parallel rays in unfamiliar to you, stay tuned to my YouTube channel because I will be releasing a video on this topic in the coming months.

As for your list of ‘Advantages’ I don’t agree - you can customise the light and develop new lighting techniques with non-infinity microscopes as well (just see some of the videos on my YouTube channel for practical examples of that) and you can buy quite inexpensive generic objectives for 160 mm tube length microscopes with an RMS thread from places like AliExpress and eBay, etc. so that is not an advantage for choosing infinity optics per se.

I wish you all the best in finding the right scope for you.

PJT