Resolution

Resolution…

I am not talking about the empty promises made in haste at the New Year’s Eve party only to be unceremoniously discarded like the last half carton of egg nog, the purchase of which had seemed like such a good idea the week before Christmas. The resolution that I want to talk about this week is the ability for an optical system to distinguish two points that are in close proximity as separate entities on our camera’s sensor. Assuming, of course, that the number and size of photo- sites on the sensor, or the light sensitive cells in our retinas, are capable of resolving detail to the same or a higher degree, the limiting factor becomes the numeric aperture of our objective  lens. The relationship between resolution and the numeric aperture of a system can be loosely defined by the formula:

Resolution =(approximately) the wavelength of light/ 2 x NA

This is just a helpful approximation, but good enough to make it clear that the higher the NA of our objective, the smaller the separation of points and the more resolving power in the system. We typically use objectives that prioritize full spectrum color correction and long working distances, as these characteristics of a lens give us much less color fringing while providing a lot of room  for illuminating our subject. A good example of this is the 5X Mitutoyo M Plan apochromatic objective. This lens has a numerical aperture of only 0.14 but the low resolving power (2um) is an acceptable trade-off for the huge working distance of 34mm.

Consider now the resolution of an objective like the Olympus UPLX APO, which has a numerical aperture of 0.8 (at 20X) - it is also  an apochromat, but can resolve to 0.42um - five times the resolution of the Mitutoyo (and more than twice the resolution of the Mitutoyo 20X SL WD which only has an NA of 0.28). It seems, therefore, that we are limited to using only lower NA objectives because the  corresponding tiny working distances make it all but impossible to get enough light onto our subject for photography to be possible.

At first blush, this appears to present us with a Hobson’s Choice - or no real choice at all. We can take it or leave it. We choose a high NA objective or a well lit subject, but not both. However, there is another option and that is going to be the subject of Thursday’s livestream. I am going to show you a practical and affordable alternative method for using high NA objectives  while also illuminating the subject for photography. This will not be a novel concept to everyone, but even for those of you who already know the answer to this perplexing puzzle, it may surprise you to discover just how accessible super-high-resolution photomicrography  can be, with a small investment and most of the same equipment you already have. Tune in to Macro Talk Too this Thursday at 2PM to get everything you need to dive into high-resolution photography! https://youtube.com/live/DHEicfFzmgE?feature=share

Let’s now work backwards to Tuesday’s Macro Talk, our first livestream this week, at 8PM on YouTube. We are going to have a Competition Results Special, in which I will discuss the entries to last month’s contest and announce the winners. I have decided to do this because my plans for judging this competition and recording the process for release in a video fell through at the last minute. My guest judge was called away on urgent business and was unable to complete the judging and recording. So I am going to go it alone this month and if I am doing that, I might as well do it live, as these livestreams are always a lot of fun to do. There were only about 35 entries this month (mechanisms was the theme) so I should have just enough time to go through every entry. Your link to the results livestream is right here - https://youtube.com/live/RQnBEEOL3CA?feature=share

This Saturday, at 10AM, we have another AfterStack - this is Episode 16 - and Bud Perrott will be back to lead this discussion. If you have an image you would like to have discussed be sure to send it to Bud or I this week. I believe Bud has a topic lined up and as soon as I find out what it is I will announce it in a livestream. This post-processing round table discussion is free of charge and open to anyone interested in attending. But you will need an invitation to get in - here it is -

Topic: AfterStack 16 Time: Feb 8, 2025 10:00 AM Central Time (US and Canada)

https://us02web.zoom.us/j/6916802815?pwd=TS9tZi9ZL1NXeVUvOUF4eTg5YjdlZz09&omn=84267941870

Meeting ID: 691 680 2815

Passcode: 678122

At the end of last week I had the distinct pleasure of meeting Zamir Pena, the inventor of the AK Diffuser and owner of the business by the same name. He is a delightful young man and our conversation covered quite a bit of ground. I decided to include a summary of my review of the AK diffuser with the interview, which will be released very soon. For anyone thinking about adding the AK Diffuser to their field macro kit, something I strongly suggest you do, Zamir has very kindly arranged to offer a discount for my viewers. This information will also be included in the video, but you can also take advantage of it now by going to:

www.AKdiffuser.com and entering the code “Allan Walls” before the end of February to get a 5% discount.

By the way, I was offered an affiliate relationship with the AKDiffuser company. I decided that this may be perceived to introduce a potential bias that could be influencing my review, so I politely declined the offer. I will not make a penny from any sales resulting from this or any future reviews or recommendations.

Finally, a word about our growing Macro Competition…

IMPORTANT REMINDER

The naming of your image is important. Failure to adhere to the requested naming convention complicates the judging process, can significantly add to the judge’s workload, and may result in errors. The required naming convention in this competition is as follows:

"TITLE” FIRST NAME.LAST NAME.FILETYPE

This is an example of the correct naming of entries for this competition -       

“Compound Eye” Allan.Walls.jpg       

The TITLE must match the name of the image used when entering the image and should be in quotation marks. Your first and last names should be separated by a full stop (period). We have not enforced this convention, but with new guest judges every month, we have to eliminate confusion about image titles and photographer’s name. So, starting with this month’s competition, failure to comply with the naming convention will disqualify the offending image. This rule will not affect entries submitted BEFORE 10AM on Sunday February 2, 2025

That is all I have for you this week and I look forward to seeing you at one of the week’s events!

Allan