New olympus 90mm 2x macro
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Re: New olympus 90mm 2x macro
or another way to look at, for a given magnification, effective aperture is independent of focal length, working distance, etc, solely depended on nominal aperture and magnification. then you can plug in effective aperture for those diffraction calculations so the larger the nominal aperture, the better if you compare two lenses at same magnification, regardless focal length, working distance, etc.
Re: New olympus 90mm 2x macro
...that means if both has same working aperture, set at same magnification, both will have same resolving power.mjkzz wrote: ↑Thu Feb 09, 2023 6:42 pmfrom Gaussian formula, the half angle of entrance cone is solely dependent on magnification and aperture, so basically, for a given magnification, it is the aperture that matters to increase resolving power, ie, reduce diffraction, that also means, for a given magnification and aperture, it does not matter what focal length the lens has, in turn again, that means if both has same nominal aperture, set at same magnification, both will have same resolving power.
Re: New olympus 90mm 2x macro
if by working aperture, you mean the aperture being set and used, which I usually refer it to as nominal aperture, to differentiate it from "effective" aperture -- it is something that is physical[edit],limited by the edge of glass or edge of iris]/edit], rather than "calculated" or "derived".JKT wrote: ↑Thu Feb 09, 2023 11:08 pm...that means if both has same working aperture, set at same magnification, both will have same resolving power.mjkzz wrote: ↑Thu Feb 09, 2023 6:42 pmfrom Gaussian formula, the half angle of entrance cone is solely dependent on magnification and aperture, so basically, for a given magnification, it is the aperture that matters to increase resolving power, ie, reduce diffraction, that also means, for a given magnification and aperture, it does not matter what focal length the lens has, in turn again, that means if both has same nominal aperture, set at same magnification, both will have same resolving power.
Actually, even the "effective" aperture is the same once mag is known for the same "working" or "nominal" aperture, but when general public compare lenses, it is hard for them to imagine "effective" aperture or the term might not even be known to them. However, to solidify comparison, instead of telling them to chose a larger lens or with longer focal length, to get "sharp" image, it is the physical nominal aperture that matters, the rest is trading off working distance, etc.
Re: New olympus 90mm 2x macro
By working aperture I mean the object side f-number in the used shooting setup. Effective aperture is same situation, but image side.
Re: New olympus 90mm 2x macro
ok, a bit too many terms used here, anyways, the (half) angle of entrance cone really depends on the physical aperture used/set and magnification, longer focal length lens might have taller/larger cone compared to shorter focal length lens, but cone angles are the same, of course, provided we are talking about equivalent "thin" lens models.
- enricosavazzi
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Delayed deliveries
OM Systems announced that deliveries of the 90 mm macro will be late by a couple of months, because demand for the lens is much higher than they expected:
https://www.43rumors.com/demand-for-om- ... eliveries/
FWIW, I have one on pre-order from OM System EU, and after the initial confirmation I received nothing official about delays.
https://www.43rumors.com/demand-for-om- ... eliveries/
FWIW, I have one on pre-order from OM System EU, and after the initial confirmation I received nothing official about delays.
--ES
- enricosavazzi
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Re: New olympus 90mm 2x macro
My M.Zuiko 90 mm macro arrived this morning, so I will soon start with the testing. I have several questions about this lens that can be answered by testing, but are not addressed by any of the reviews I have seen so far. Eventually I will publish my review on my web site (www.savazzi.net).
This also means that I might be able to answer questions about this lens from PM.net members, if they have any (answerable) questions.
This also means that I might be able to answer questions about this lens from PM.net members, if they have any (answerable) questions.
--ES
Re: New olympus 90mm 2x macro
Thanks Enrico.enricosavazzi wrote: ↑Thu Mar 02, 2023 4:46 amThis also means that I might be able to answer questions about this lens from PM.net members, if they have any (answerable) questions.
I will be very interested to know if this 90mm lens presents some vignetting (hard, soft or null) as tube lens in a combination with microscope objective like Mitutoyo X10.
It would be useful for me to get a tube lens with short focal distance on my Olympus/OMD system for microphotography (focus bracketing).
Re: New olympus 90mm 2x macro
That is a really good question! This lens could be magical when used with a microscope objective and automatic focus bracketing. Its FOV is close to the FF standard 200mm tube lenses.jojm wrote: ↑Fri Mar 03, 2023 1:54 amThanks Enrico.enricosavazzi wrote: ↑Thu Mar 02, 2023 4:46 amThis also means that I might be able to answer questions about this lens from PM.net members, if they have any (answerable) questions.
I will be very interested to know if this 90mm lens presents some vignetting (hard, soft or null) as tube lens in a combination with microscope objective like Mitutoyo X10.
It would be useful for me to get a tube lens with short focal distance on my Olympus/OMD system for microphotography (focus bracketing).
- enricosavazzi
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Review now online
My review of the M.Zuiko 90 mm f/3.5 Macro IS Pro: https://www.savazzi.net/photography/omsys90macro.html
It is not yet public (in the sense that it is not indexed in the sitemap, nor linked to by other pages) and a few things may still change, but by and large it is done.
I have not tested it as a tube lens yet, but my impression is that it would be overkill, besides probably costing more than a new Mitutoyo M Plan Apo. As a tube lens it would only cover Micro 4/3 (and perhaps cause a Mitutoyo objective to vignette), but a Mitutoyo M Plan Apo on a good 200 mm tube lens already matches the resolution of a 20 Mpixel Micro 4/3 sensor. So I cannot avoid wondering what practical use there would be for the added lp/mm resolution of pushing the objective down to less than half its nominal magnification with this 90 mm as tube lens.
It is not yet public (in the sense that it is not indexed in the sitemap, nor linked to by other pages) and a few things may still change, but by and large it is done.
I have not tested it as a tube lens yet, but my impression is that it would be overkill, besides probably costing more than a new Mitutoyo M Plan Apo. As a tube lens it would only cover Micro 4/3 (and perhaps cause a Mitutoyo objective to vignette), but a Mitutoyo M Plan Apo on a good 200 mm tube lens already matches the resolution of a 20 Mpixel Micro 4/3 sensor. So I cannot avoid wondering what practical use there would be for the added lp/mm resolution of pushing the objective down to less than half its nominal magnification with this 90 mm as tube lens.
--ES
Re: Review now online
The advantage is that you could use it in the field with automatic focus bracketing. As I mentioned earlier, this is a huge benefit, though it is probably only practical with a 5x objective or less.enricosavazzi wrote: ↑Sat Mar 04, 2023 1:00 pmI have not tested it as a tube lens yet, but my impression is that it would be overkill, besides probably costing more than a new Mitutoyo M Plan Apo. As a tube lens it would only cover Micro 4/3 (and perhaps cause a Mitutoyo objective to vignette), but a Mitutoyo M Plan Apo on a good 200 mm tube lens already matches the resolution of a 20 Mpixel Micro 4/3 sensor. So I cannot avoid wondering what practical use there would be for the added lp/mm resolution of pushing the objective down to less than half its nominal magnification with this 90 mm as tube lens.
In addition, I don't understand your reasoning on its value for pushing down an objective. As you know, the FOV of an objective on MFT with a 90mm tube lens is about the same as the FOV of the same objective on a 180mm tube lens on FF. This is very close to the the FOV you get with the same objective and a 200mm tube lens on FF. In other words, this new 90mm lens, if it does not vignette, almost exactly replaces the 200mm + FF system. That's very useful. And it hardly counts as pushing down, in terms of lines per FOV. Lns per mm is not the appropriate measure when comparing across sensor sizes.
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Re: Review now online
My reasoning is that an M Plan Apo 10x with 200 mm tube lens already fully utilizes the resolution of a 20 Mpixel Micro 4/3 sensor. By pushing down the magnification with a 90 mm tube lens, you do get more than twice the lp/mm in the optical image (the total number of lp across the field of view of the objective remains the same, but the field of view shrinks in absolute size). The optics project an image containing much finer detail on the Micro 4/3 sensor, but the sensor was already at its resolution limit with a 200 mm tube lens and cannot record any more detail.Lou Jost wrote: ↑Sat Mar 04, 2023 2:03 pmThe advantage is that you could use it in the field with automatic focus bracketing. As I mentioned earlier, this is a huge benefit, though it is probably only practical with a 5x objective or less.enricosavazzi wrote: ↑Sat Mar 04, 2023 1:00 pmI have not tested it as a tube lens yet, but my impression is that it would be overkill, besides probably costing more than a new Mitutoyo M Plan Apo. As a tube lens it would only cover Micro 4/3 (and perhaps cause a Mitutoyo objective to vignette), but a Mitutoyo M Plan Apo on a good 200 mm tube lens already matches the resolution of a 20 Mpixel Micro 4/3 sensor. So I cannot avoid wondering what practical use there would be for the added lp/mm resolution of pushing the objective down to less than half its nominal magnification with this 90 mm as tube lens.
In addition, I don't understand your reasoning on its value for pushing down an objective. As you know, the FOV of an objective on MFT with a 90mm tube lens is about the same as the FOV of the same objective on a 180mm tube lens on FF. This is very close to the the FOV you get with the same objective and a 200mm tube lens on FF. In other words, this new 90mm lens, if it does not vignette, almost exactly replaces the 200mm + FF system. That's very useful. And it hardly counts as pushing down, in terms of lines per FOV. Lns per mm is not the appropriate measure when comparing across sensor sizes.
An advantage I can see in alternating between a 200 mm and a 90 mm tube lens is that you get two magnifications from one 10x objective (10x and 4.5x). A 5x objective on a 90 mm tube lens gives you a 2.25x magnification, only marginally higher than the native 2x magnification of the lens, and with the 90 mm you can do focus stacking both with and without the 5x objective, plus you get IS only without the objective. Probably not worth the effort of using a 5x objective.
Granted, in-camera focus stacking/bracketing with a 7.5x or higher objective can potentially replace a motorized rail. A tripod and some sort of precision positioner are still needed with an added microscope objective, because IS is not designed for the resulting high magnification.
--ES
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90 mm as tube lens
Initial tests with the Mitutoyo M Plan Apo 10x are not so encouraging. The 90 mm is focused at infinity. The objective is attached via a stack of three adapters that puts it close to the front element.
I focused on the 228 lp/mm lines. There is some sagging of the camera, probably because I attached the latter to the stand, instead of using the lens collar. The opposite side of the resolution target is somewhat out of focus.
Whole image, reduced. There is a clear darkening in the corners.
1:1 crop. Resolution is not the best. This is close to the top margin, and there is a clear lateral chromatic aberration. The target is labeled in lp/mm.
PS- My tests of the 90 mm with MC-20 teleconverter (total magnification 4x) gave a better result at f/10 (total), especially for what concerns contrast and resolution. No doubt one must factor into this the fact that the camera is automatically correcting lateral chromatic aberration in this case.
Working distance at 4x with the MC-20 is more than twice the working distance of the Mitutoyo 10x (total magnification 4.5x), albeit the latter obviously has a much narrower "nose".
I focused on the 228 lp/mm lines. There is some sagging of the camera, probably because I attached the latter to the stand, instead of using the lens collar. The opposite side of the resolution target is somewhat out of focus.
Whole image, reduced. There is a clear darkening in the corners.
1:1 crop. Resolution is not the best. This is close to the top margin, and there is a clear lateral chromatic aberration. The target is labeled in lp/mm.
PS- My tests of the 90 mm with MC-20 teleconverter (total magnification 4x) gave a better result at f/10 (total), especially for what concerns contrast and resolution. No doubt one must factor into this the fact that the camera is automatically correcting lateral chromatic aberration in this case.
Working distance at 4x with the MC-20 is more than twice the working distance of the Mitutoyo 10x (total magnification 4.5x), albeit the latter obviously has a much narrower "nose".
Last edited by enricosavazzi on Sun Mar 05, 2023 6:33 am, edited 2 times in total.
--ES
Re: New olympus 90mm 2x macro
Enrico, the increased field of view obtained by pushing down is often important. And the fact that it will out-resolve the sensor means that pixel-shifting can be used.
Thanks for the initial tube lens test. Somewhat discouraging. Darn.
Thanks for the initial tube lens test. Somewhat discouraging. Darn.
- rjlittlefield
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Re: Review now online
That seems like overstating the case.enricosavazzi wrote: ↑Sun Mar 05, 2023 3:44 amMy reasoning is that an M Plan Apo 10x with 200 mm tube lens already fully utilizes the resolution of a 20 Mpixel Micro 4/3 sensor. By pushing down the magnification with a 90 mm tube lens, you do get more than twice the lp/mm in the optical image (the total number of lp across the field of view of the objective remains the same, but the field of view shrinks in absolute size). The optics project an image containing much finer detail on the Micro 4/3 sensor, but the sensor was already at its resolution limit with a 200 mm tube lens and cannot record any more detail.
When I run the numbers, I get these results:
20 megapixels on Micro 4/3 sensor gives pixel pitch = 3.49 microns [=sqrt(18*13.5/20000000)].
lambda = 0.55 microns.
NA = 0.028 gives diffraction cutoff at 0.98 microns per cycle on subject [=lambda/(2*NA)].
At 10 X, diffraction cutoff at sensor is 9.8 microns per cycle, giving 2.8 pixels per cycle.
At 4.5X, diffraction cutoff at sensor is 4.4 microns per cycle, giving 1.27 pixels pre cycle.
By these numbers, it seems to me that the 10X image is definitely not fully utilizing the resolution of the sensor.
I expect that you're using some different calculation.
What is it?
--Rik