Limnochares aquatica, Sessilida

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Fero
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Limnochares aquatica, Sessilida

Post by Fero »

Hello all,
I have registered only a week ago with a goal to learn more on ultramacro photography and microphotography. Today I have spent some hours to try the setup I have: Laowa 2,5-5x and my Canon EF 100/2,8 macro with extension tubes and I must say 100mm macro is really a nice lens.

This shot was made using direct flash, ISO 100 1/200s f/11 and 61mm extension tubes so aroun 2,5x magnification on my APS-C EOS80D, this is full frame without cropping. I want to try EF 100mm with an objective lens. It has to be infinity corrected objective? I have Plan 4/0.1 160/0.17 and Akashi M10 0.25/210 objectives, can they be used? I would like to go to higher magnifications.
Image

This shot was made using Laowa 2.5-5x at 5x, 1/200s, ISO 100, f/4, direct flash from edge to increase contrast as these creatures are translucent. Magnification should be 8x. This is slight crop
Image

leonardturner
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Re: Limnochares aquatica, Sessilida

Post by leonardturner »

I very much like your first image, and am surprised that you got such a good result with direct flash without diffusion. I am not familiar with Akashi objectives, but in general an infinity objective requires a tube or intermediate lens whereas a non-infinity objective can be used without. The tube lens should ideally provide about 200mm, and less than that would decrease your magnification.

Leonard

MarkSturtevant
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Re: Limnochares aquatica, Sessilida

Post by MarkSturtevant »

Impressive depth of focus on the first one!
Is the second Vorticella?
Mark Sturtevant
Dept. of Still Waters

Fero
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Re: Limnochares aquatica, Sessilida

Post by Fero »

@leonardturner - sorry missed your reply - the photo was taken in a white ceramic pot, so the light got difused all around, the backgroun has been selected and changed to black (if I remember, strangely I can not find original photo),
@MarkSturtevant - the second photo is I think from order Sessilida but unfortunatelly I have no closer ID

Lou Jost
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Re: Limnochares aquatica, Sessilida

Post by Lou Jost »

I like the second one very much. I am curious, how did you get 8x? Did you use extension on the Laowa?

Fero
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Re: Limnochares aquatica, Sessilida

Post by Fero »

Hi, I used 5x on APS-C sensor, that should be 8x (5x * 1.6x = 8x)

Lou Jost
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Re: Limnochares aquatica, Sessilida

Post by Lou Jost »

Hi, I used 5x on APS-C sensor, that should be 8x (5x * 1.6x = 8x)
While the crop factor affects the field of view, it does not change the magnification of the image on the sensor. We'd say this was still a 5x picture. After all, we are all looking at this image on differently sized devices, so we can't give a single m that describes the relationship of the object size to the "image size as viewed". The relation between the object size and the image size on the sensor, on the other hand, is well-defined.

I like giving the width of the field of view along with the conventional magnification ratio. In terms of the final result, it is the width of the FOV that matters, not the sensor size. Especially when we are comparing results from different-sized sensors. But alas most people don't do that, I suppose because most people use just a single sensor size. But we can calculate the FOV if the person tells us the m and the sensor size.

Fero
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Re: Limnochares aquatica, Sessilida

Post by Fero »

I think I described accuratelly how I took the photo ;-)
But as for magnification I do not fully agree, the sensor crops the field of view 1.6x (in my case), hence increasing magnification by 1.6x (compare to 35 mm). Also when I use 100 mm macro at 1:1 I get 1.6x effective magnification, if you would use this on even smaller sensor you get even higher magnification. But I agree it is more or less same if you crop from full format 1.6x.

Lou Jost
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Re: Limnochares aquatica, Sessilida

Post by Lou Jost »

the sensor crops the field of view 1.6x (in my case), hence increasing magnification by 1.6x (compare to 35 mm)
It just crops it, it doesn't change the actual magnification of the image on the sensor relative to the subject. "Magnification of the image on the sensor relative to the subject" is how magnification is almost universally defined in the technical photographic literature. Your definition is perfectly understandable, but it uses an arbitrary standard. Kind of like using "equivalent 35mm equivalent focal lengths" when describing lens focal lengths. Your lens has the same focal length on all cameras, regardless of sensor size. But the FOV depends on sensor size. Relative measures like this can be helpful but they use an arbitrary standard and can be misleading.

If you use your definition for m, you may get errors when you put that m into optical formulas involving m.

Fero
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Re: Limnochares aquatica, Sessilida

Post by Fero »

I fully understand but, with 100 mm on full frame I have to be closer for the same magnification in comparison with APS-C and that gives totally different perspective and f/8 on APS-C is the same as f/16 on full frame in terms of depth of field and sharpness (difraction). thaht is why you perhaps find nice DOF on my photo for f/8. I agree that if shot from the same distance with the same focal lenght that APS-C is just a crop but theproblem is you never shoot same subject from the same distance with the same focal length, that is why you have greater DOF on smaller sensors.

Fero
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Re: Limnochares aquatica, Sessilida

Post by Fero »

Also what came to my mind is microscopic objectives, they do not use 35mm equivalent standard, so 2x on the microscope is not the same as 2x on the full frame, or is it? But I agree we should use same standard so from now on I will define lens magnification + sensor size and will not recalculate for APS-C

Scarodactyl
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Re: Limnochares aquatica, Sessilida

Post by Scarodactyl »

Just quote field of view, it is universal. 'Magnification' is too vague if you aren't speaking in a particular technical context. Even on a microscope the field of view at a given magnification can vary a lot since eyepiece/objective field numbers vary from 15mm or less on an antique system to 18-22 on a more recent standard system to 26.5mm on a typical ultra widefield modern one or 28-30mm on a rarer specialized system.

Fero
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Re: Limnochares aquatica, Sessilida

Post by Fero »

Thanks a lot, yes, I think this is the best ;-)

rjlittlefield
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Re: Limnochares aquatica, Sessilida

Post by rjlittlefield »

Fero wrote:
Sat Jul 10, 2021 2:13 pm
f/8 on APS-C is the same as f/16 on full frame in terms of depth of field and sharpness (difraction). thaht is why you perhaps find nice DOF on my photo for f/8. I agree that if shot from the same distance with the same focal lenght that APS-C is just a crop but theproblem is you never shoot same subject from the same distance with the same focal length, that is why you have greater DOF on smaller sensors.
That description is sort of correct, but there are some issues that it may be helpful to clarify.

For same DOF and diffraction, the exact condition is that effective f-number scales in proportion to linear sensor size. So effective f/16 on full frame is equivalent to effective f/10 on a 1.6X crop sensor. For cameras that work in nominal f-number, not automatically corrected for magnification, the calculation of exactly equivalent nominal f-numbers can be challenging. Even with the same sensor size, f/8 at 1:1 on a Canon is likely to be about the same as f/16 on a Nikon, because in that case the "f/8" and "f/16" actually mean two different things.

With your equipment, the setting that you list, "f/11 and 61mm extension tubes so aroun 2,5x magnification", gave around effective f/38. That puts the optical image far into diffraction territory on the APS-C sensor, but of course it looks sharper when downsized for web viewing.

In any case, the key concept is that all cameras, regardless of sensor size, lie on the same curve that expresses the tradeoff between depth of field and diffraction blurring.

The reason why smaller sensors often give greater DOF is a quirk of how people set their cameras, that results in a narrower entrance cone with the smaller sensor. Perhaps the most fundamental reason is that large sensors can collect more photons, and people are used to settings that try to fill them up. This is often expressed as some guideline like "Use base ISO, and expose to the right." Accomplishing that goal, while using the same illumination levels and exposure time, ends up giving a narrower entrance cone with the smaller sensor. The same image can be shot with the larger camera by stopping down more and using higher ISO to keep the same shutter speed, but people with larger sensors often either don't think of that idea in the first place, or reject it as unpalatable if suggested.

--Rik

Fero
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Re: Limnochares aquatica, Sessilida

Post by Fero »

Hi Rik,
I think I understand this basic concept, but reality is often different. I found this article very good: http://extreme-macro.co.uk/microscope-objectives/
I wonder why f/8 on Canon relates to f/16 on Nikon?
I was thinking to buy full frame to get better DOFm but than I realized that for the same magnifiaction with 100 mm macro I would need to go closer so I do not gain higher DOF, but perhaps if I shoot from the same distance and crop to APS-C size I might get higher DOF.
Currently I am playing with microscopes and also bought Mitutoyo 2x and 5x but did not have time to try them.
I bought a set of GF-Planapochromats from CZ Jena with great NA, the best ones are 25x/0.65 and 63x/0.90 but did not have time yet to play with them.
Last edited by Fero on Thu Jul 15, 2021 2:56 pm, edited 1 time in total.

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