This “Pristine” Objective Hides a Horrifying Plague (Updated)

Introduction

Frustration often leads to irrational decisions. An eBay seller has been listing loads and loads of objectives recently, none of which I have been able to get my hands on. A lot of them end at frankly ridiculous prices for the given condition and sketchy origin. Instead, I turned to a well-known source that has screwed over two that I know of.

This company is called “亞輝 (ya hui)”, one of the largest Chinese surplus dealers in the mainland. I would say, at least 80% of stolen listings on eBay comes from this source. They are a company that buys and sells industrial equipment, they have many employees each operating under their own stores on Taobao. Often or not, the photos will not match the item one will receive, which they will attribute to large inventory and photos being there as a reference. Obviously, this is not allowed on eBay as “items are not as described” is a valid reason to initiate a return, regardless of what the seller tries to conjure up.

Originally, I thought I identified optical flaws. After crucial information provided by the user “abednego1995” on photomacrgraphy.net, I realised my mistakes. I am no expert, however, I strive for accuracy and integrity.

The Objectives

Below, on the left, is the “Olympus UPlanSApo 10x (SA10)” objective I purchased, for roughly $500, the typical market value on eBay. On the right, you can see my “Olympus UPlanFL N 10x Ph1 (FLN10P1)” objective I purchased new from a good mate locally. Both of these are UIS2 and I intend to use them for differential interference contrast (DIC). The green text seen on the right indicates it is designed for phase contrast, featuring a phase ring internally.

You can see the nasty “warranty” sticker below. I always tear these despicable eyesores off.

Looking under the mask

Apart from subtle colour differences and both being a fingerprint magnet, they are identical in terms of condition. That is true until some illumination in the dark.

What are those dots! This is a sign of delamination, the substance used in cemented couplets are going bad. Luckily, this is not fungi which spreads, but it may or may not be detrimental to image quality. UIS2 objectives have only been around for less than a decade, how can something that new show such traces? I do not know. Maybe the objective was used with lasers, it is rather common for labs to use biological microscope objectives with lasers due to their lower cost. One may think researchers working in a lab have massive budgets or they have vast technical knowledge relating to microscopes. This is not always true, just look at the infinity objectives mounted on a BH2 without a tube lens at my workplace. Luckily, it is not used, we prefer that bigger Zeiss microscope.

Those dots indeed give off a scary impression, they exist within the objective itself, on the internal optics. With illumination from the beforementioned user on the photomacrography forum, these dots are a normal occurrence. UIS2 objectives were also released in 2004, making them one decade and a half old (17 years if we count 2004 as an entire year!). Olympus utilise internal paintings to counter destructive internal reflections. Such reflections are colloquially referred as “stray light”, which cause glare and loss of contrast. It is important to eliminate stray light in imaging. Such applications are crucial to telescopes and tube fittings used for objective lenses.

These dots do not exist in the back focal plane (BFP), nor are they visible from the exit pupil. They are a consequence of black coatings applied to the periphery of the very front of the first optic. Below is a snapshot from the patent of this objective. I need to learn methods to look up such patents, new objectives directly purchased from the manufacturer and their distributors are usually not an option due to high cost. These patents will be critical when I examine the objective’s physical condition.

US patent US7158310B2

The figure above is the optical formula of the SA10 objective. The black paint is applied to the periphery of r_1, which corresponds to the optical element d_1. The dots are entirely normal, and even exist in new objectives. This is a purely cosmetic issue, and will not hinder its performance at all.

Testing

Here are my test results. The first set features a resolution target, 360 lp/mm. Nikon tampers with the raw files with the 400 lp/mm target, trying (and failing) to fix moiré due to the lower resolution of the Z6. Sharpening is set to zero and highlights are dragged down a bit. Only the centre is presented here because that is what I care about. The SA10 objective requires a 0.17mm coverslip. I always wondered if it truly mattered since a numerical aperture (NA) of 0.4 is not that large. For an NA of 0.7 and beyond, lacking the coverslip absolutely destroys the images.

Moreover, I do not have an adequate way to mate my resolution chart with the coverslip, typically, refractive index matching liquid is used. Canadian Balsam is a rather adequate liquid here, having a refractive index similar to typical coverslips. I have no access to those, so there is an air gap between the coverslip and the resolution chart which technically is not ideal.

Click HERE for the original image. As you can see, clearly the SA10 is better. The comparison is not entirely fair, the phase ring in the FLN10P1 will decrease contrast and have a negative impact on image quality. The SA10 has more contrast and resolution. Surprisingly, I can only see a difference in image quality when a coverslip is used at 600%! Even at 200%, I struggle to see a difference. I did a blind test where I closed my eyes and cycled through randomly, opened my eyes to try and guess, that did not work out well. I cannot tell the difference.

I do not think this is true for higher resolution cameras. According to the literature[1], any objective with an NA greater than approximately 0.3 needs the coverslip. I will try this objective for reflected light focus stacking during the weekends.

Figure above, 600%, with coverslip on the right. There is a slight loss in contrast and sharpness. I realised the NA on my condenser was a bit low, it was set at 0.3 for the FLN10P1. I dialled to 0.4 and the difference is even smaller. This time, however, I did pass the blind test.

Now for some real-world DIC, how does the SA10 stack up against the FLN10P1? Below is an excellent diatom arrangement by Klaus D. Kemp, a skilful and knowledgeable British Diatomist.

It is hard to see a difference now, unless at 100%. The SA10 still edges out, more overall contrast and clarity, more resolving. Bigger image HERE.

Below is the ovary of a poppy, traverse section. This is a vintage slide prepared by Arthur J. Doherty, stained with carmine, “Balsam and Benzole” mountant.

This time, the difference is quite clear. Bigger image HERE. The SA10 as the trend would suggest, wins.

Conclusion

Overall, the SA10 is a strong piece of optic. I am delighted that it works as intended. The NA of the SA10 is 0.4, only 0.1 above the FLN10P1. I was surprised at the performance even when a coverslip was lacking. This objective could replace popular Mitutoyo metallurgical objectives, further testing is crucial. The test however does not apply to normal UPlanFL 10x objectives, normal brightfield objectives will not suffer from loss in contrast due to an internal phase ring.

While I am certainly not happy with the purchase, I am going to keep the objective. Initiating a return and sending it all the way back to China is going to cause some major headaches and unneeded paranoia, especially since covid-19 is still around. Staying indoors can already cause temper and depression issues due to the lack of exposure to sunlight. I will try and negotiate a small refund however, it was presented as optically clear and I am on good terms with that specific Yahui employee. The boss of that company is a massive ✨✨✨hole, some of their employees however are really friendly and helpful. If they change face when I try and initiate the refund, I will just laugh at how gullible I am.

This fiasco taught me an important lesson. I was fairly confident in my judgement and I will always go out of my way to hyper-analyse second hand objectives I have purchased. I was wrong, oblivious from the facts due to ignorance. Luckily, someone that is far more educated stepped in and corrected me. I was saved a confrontation with the seller and potential trouble since I intended to initiate a partial refund. If the refund is permitted by the seller, it would have been unfair, as these dots are a normal occurrence among certain models.

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