MicrobeHunter.com Microscopy Forum

Looks interesting Michael but above my head as well. I came across some relevant comments from A.E. Conrady in 1923. First on the thought to use the lesser of the NAs by analogy with Airy's analysis of the telescope and how that doesn't work: When applied to the microscope, Airy's theory of the spur...

Oh yeah, Goldstein was referencing Martin's book there, I didn't make that connection earlier. (I haven't tried to exhaustively follow references backward or forward.) I believe I read somewhere a rule of thumb that viewers typically judge subjective best image quality to be around either 1/3 or 2/3...

I had not seen either of those references, thanks Glenn. Zieler's book seems quite obscure but it is on archive.org. Not freely available but with an account it can be "borrowed" in 1 hour increments for online reading. Regarding critical vs. Nelsonian illumination, I have not read much about the hi...

I didn't intend that post to be argumentative or contradictory. My post actually sought to throw some light on why higher N.A. objectives aren't necessarily limited by a condenser acting like a gate valve. Abbe was just part of the fabric of the theoretical thinking in that regard. I can't say I fol...

At the time Abbe published his paper on microscope resolution , and he published no equations, Zeiss were not using condensers. In fact, it has been reported that customers were complaining that they had to modify Zeiss microscopes by adding condensers from other makers. It is not surprising then, ...

Vintage diatom slides are generally not expensive. SEM images will help to determine if you are seeing aberrations or resolved structures. Yeah, I was going to buy some a while back but then got busy with other things and stopped watching my eBay searches. In any case, I think all the suggestions t...

I agree about all the practical difficulties of getting a really accurate prediction. However I would also point out that theoretical predictions, even if not extremely accurate, help troubleshoot practice. All those conditions and variables you point out are potential mistakes to be made. Theory ca...

The Gold Standard for specimens that demonstrate resolving capabilities is the Pluerosigma diatom. It is very easy to see the impact of reducing the NA of the objective by closing the condenser. You will be better off using diatoms as resolution targets. I don't have any diatom slides but I think t...

I personally refuse to use this formula simply because a 1.4 NA Apl-Achr condenser fully open coupled with a 4x at 0.1 NA will not yield 0.75 NA. There seemed to be some confusion on this in the papers and other stuff I looked at, but generally as far as I understood the averaging rule (especially ...

I'm having trouble following the points you are making and many of the things you are bring up in newer posts are things I already replied to earlier. I copied/pasted quite a bit of stuff below to try to get it in one place and keep track of what you are talking about. Can anyone provide a clear mat...

..,and it may be necessary to use a small angle of light to render it visible, an imperfect image being better than none at all. And most importantly, doing so (even with very small condenser NA) does not reduce resolution nearly as much as 0.61 * λ / min(NA_obj, NA_cond) predicts. It appears to me...

Sorry I don't recall who made the comment above, but I think rather than averaging the NA, NA objective +NA Condenser/2 the better outcome is realized by taking the lowest NA and using that as the base line for computation. A 1.40 objective with a 0.95 condenser would never realize a resolution of ...

Yeah, the situation with partially coherent illumination is just inherently pretty difficult to analyze, it seems. I would guess two reasons for the averaging rule persisting despite wide acknowledgement that the physical basis for it (oblique coherent illumination of a grating object) gives only a ...

I'm thinking that a lot of the confusion around this is coming from too closely equating the concepts of resolution and NA and using the terms somewhat interchangeably. NA is an arbitrarily-defined quantity which useful because when you express other quantities in terms of NA the formulas/equations ...

I started a separate thread because the very specific question in the title has noting to do with eyepiece magnification, apparent or angular field or view, exit pupil, or anything else like that. I also didn't want to further clutter up that other thread where Wayne was sharing info on the Poly* mi...

Thanks for confirming. Most of the introductory guides on the internet say something about measuring in the intermediate image plane without saying explicitly what should be done if the size of the intermediate image is modified in the eyepiece. I have always assumed FN = FOV * magnification should ...

The common equation for resolution of a condenser+objective combination, as seen in the Thor Labs link, is highly idealized, containing only 3 variables (wavelength and the NA's), and hence seems more like a simple rule-of-thumb than one that can deal with real-life complexities (such as the subjec...

Continued from Do I need another objective? #53 I agree that the averaging "feels wrong" at first glance, maybe especially so when coming from some other technical background. I had the same initial reaction. Regarding waiting for someone with real knowledge, Abbe's ghost, etc... science has been pr...

Oil is commonly used with microscopes at optical interfaces because its refractive index (RI) is higher than air (~1.5 vs. ~1). This allows light to be bent at a sharper angle than at glass-air interfaces (otherwise the rest of the light would be reflected internally). The sharper angle allows a br...

A dry (air-gapped) condenser will strictly limit the effective NA of any subsequent objective to a theoretical maximum of 1 (meaning somewhat less than 1 in practical terms). Where did you read this? The average thing is everywhere in guides and textbooks, it's just rare that they attempt to explai...

I’ve wondered about the formula that suggests that when condenser NA is lower than Objective NA the result is an average of the two. Intuition suggests that NA should revert to the lower of the two. Does anyone know if there is a mathematical basis for the averaged formula? I wondered the same thin...

Quick follow up question/clarification regarding: ... The FN is the field diaphragm of the eyepiece. ... (I never understood where the positive/negative terminology for this classification of eyepieces comes from, but anyways...) In a Huygens eyepiece, for example, where the field lens before the fi...

No , we aren't talking apples and apples. ... I will rephrase that because either I jumbled the words or you misunderstood them. A 15X/20 eyepiece produces an image circle that is the same size that a 10X/30 eyepiece would produce. I don't think it can ever be apples to apples unless you specify mo...

Only if the camera was in my eye. The image circle at the enrance to the eye is 20mm. If you hold a quarter out at arms length it will obscure the moon but if you bring it right close to your eye it will obscure a third of the sky. I thought this 20 mm was some physical measurement you personally h...

Of course. You are viewing the exit pupil from what, 10 inches away with a camera lens. I don't know where uou have your screen. My point was that the apparent field your eye sees right st the cornea is 20mm. Put the scale at your eye. The strip of lens paper being projected onto is at the exit pup...

Ok, so to clarify: The entire theory revolves around the 10X eyepiece. The descriptions of how the F.N. system works are carried out using a hypothetical 1X objective and 10X eyepiece. Measure the exit pupil of a 10X/20 eyepiece and see what you get. Only with the 10X eyepiece can you easily and qui...

First question: ...and the 4/5/7 reflect the height index 4 in the first position supports a 25mm FN eyepiece, the 5 is 22mm FN the 7 supports a 20mm FN. All intermediate image components, those that mount between the objective ba and the tube lens. had a corresponding height index number and and su...

I think the confusion is here: If you measure a 20 F.N.field viewed through a 10X eyepiece at your eye : the actual diameter of the viewed field, with a transparent scale or ruler right as the image enters your eye, it will measure 20mm. ... A 20mm F.N. with a 15X eyepiece will measure 30mm and a 20...

Since the FN discussion started with what is considered "supported" I would point out that in this example: It is a system that is base 10, so it doesn't represent the real field vs. apparent field circmstance for a 15X or a 5X eyepiece intuitively. An easier way to visualize it is if the 15X eyepie...

The tiny set screws that fix tube length on the nonadjustable eye tube on are the same 4-flute 0.048" McMaster 7048A12. The four screws holding the shroud covering the IPD adjustment are 6-flute 0.060" McMaster 7048A65. I don't remember if there are any others on the series 10 heads. I also have a 6...