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e6filmuser
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p.1 #1 · p.1 #1 · Trichia decipiens Fruiting Bodies


These shiny, pale orange spheres on short stalks are the unripe fruiting bodies of a common slime mould, found on rotten wood. This set is with my latest high magnification setup, which gives a FOV 5mm wide:

EM-1 (manual setting), Olympus 4/3 x2TC, Olympus 4/3 50mm f2 macro, Raynox MSN-202 25 diopters, triple flash, hand-held. The effective aperture was f22 (f11 on the lens).

There is very little DOF to play with for different shooting angles but the crosseye stereo works to some extent.

Harold





Harold Gough 2017





Harold Gough 2017





Harold Gough 2017



Edited on Mar 28, 2017 at 08:38 AM · View previous versions



Jan 16, 2017 at 06:44 AM
surfnron
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p.1 #2 · p.1 #2 · Trichia decipiens Fruiting Bodies


Well done and neat Harold ~ Ron


Jan 16, 2017 at 01:41 PM
Archibald
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p.1 #3 · p.1 #3 · Trichia decipiens Fruiting Bodies


Interesting subject. What was the magnification? (Must have been around 3x if the FOV was 5mm...)


Jan 16, 2017 at 07:40 PM
e6filmuser
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p.1 #4 · p.1 #4 · Trichia decipiens Fruiting Bodies


Archibald wrote:
Interesting subject. What was the magnification? (Must have been around 3x if the FOV was 5mm...)


7x with crop factor, 3.5x at sensor.

Harold



Jan 16, 2017 at 09:05 PM
Archibald
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p.1 #5 · p.1 #5 · Trichia decipiens Fruiting Bodies


So the effective aperture was (3.5+1) * 11 = 50.


Jan 16, 2017 at 09:14 PM
e6filmuser
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p.1 #6 · p.1 #6 · Trichia decipiens Fruiting Bodies


Archibald wrote:
So the effective aperture was (3.5+1) * 11 = 50.


Interesting thought. I quote the digital readout for the lens combination, as used. I don't know if, as a macro lens, it takes magnification into account. The lens has no aperture ring so I know only what it tells me.

Harold



Jan 16, 2017 at 09:47 PM
Archibald
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p.1 #7 · p.1 #7 · Trichia decipiens Fruiting Bodies


e6filmuser wrote:
Interesting thought. I quote the digital readout for the lens combination, as used. I don't know if, as a macro lens, it takes magnification into account. The lens has no aperture ring so I know only what it tells me.

Harold


I don't know either! I guess some do and some don't.



Jan 16, 2017 at 09:57 PM
e6filmuser
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p.1 #8 · p.1 #8 · Trichia decipiens Fruiting Bodies


Archibald wrote:
I don't know either! I guess some do and some don't.


Some further thought. (I am not an evening person and can be a bit slow!).

There are two potential issues here with effective aperture:

a) Does the lens adjust the readout for aperture by allowing for its extension? Probably.

b) (Which I overlooked above). The 25 diopters will affect the magnification and, thus, the effective aperture. So many times, I have seen it stated that a supplementary lens does not affect exposure but this is untrue, any given change in magnification (by whatever means*) having an identical effect on exposure and any potential diffraction from the reduced aperture (real or effective, including any crop factor).

So, my figure for effective aperture, as arising from use of the 2xTC was correct but it was not the whole story and your calculated value looks about right, except that you should use 7 instead of 3.5, to allow for the crop factor.

When it comes to practicalities, I am interested in the FOV and DOF, plus diffraction, when it arises.

Thanks for the nudge.

Harold



Jan 16, 2017 at 10:14 PM
 

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Archibald
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p.1 #9 · p.1 #9 · Trichia decipiens Fruiting Bodies


Nikon lenses show effective aperture, Canon lenses don't. No idea about Olympus. But the diopter will change the effective aperture, and I doubt the camera will know it is there, so won't correct the aperture.

For calculations, always use the REAL magnification, which is image size/subject size.



Jan 16, 2017 at 10:29 PM
Archibald
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p.1 #10 · p.1 #10 · Trichia decipiens Fruiting Bodies


Anyway, looking at the quality of the pics, I don't think they were shot at an effective aperture as small as 50.


Jan 16, 2017 at 10:37 PM
Archibald
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p.1 #11 · p.1 #11 · Trichia decipiens Fruiting Bodies


The effective aperture depends on the magnification and the infinity aperture of a lens. If you mount a closeup lens, the entrance pupil increases. Try it and see while looking at the front of the lens. Therefore the aperture becomes bigger (the aperture number goes down).

So if the Olympus was reporting an effective f/11, the real effective aperture including the effect of the closeup lens, might have been something bigger, like f/8.



Jan 17, 2017 at 12:44 AM
e6filmuser
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p.1 #12 · p.1 #12 · Trichia decipiens Fruiting Bodies


Archibald wrote:
The effective aperture depends on the magnification and the infinity aperture of a lens. If you mount a closeup lens, the entrance pupil increases. Try it and see while looking at the front of the lens. Therefore the aperture becomes bigger (the aperture number goes down).

So if the Olympus was reporting an effective f/11, the real effective aperture including the effect of the closeup lens, might have been something bigger, like f/8.


Ah. This brings me back to:

https://m.flickr.com/#/photos/johnhallmen/4320502042/in/favorites-nikonboi/

Scroll down a long way to find "Why Summar 12cm f4.5 + Raynox 12 diopter becomes SumRay 50mm f1.9"

This has been lurking in the back of my mind for years. I have two copies of the Summar, with the "SumRay" in mind. I seem to have stumbled across an alternative, with AF and no need for bellows.

Interesting!

Harold



Jan 17, 2017 at 06:36 AM
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p.1 #13 · p.1 #13 · Trichia decipiens Fruiting Bodies


e6filmuser wrote:
Ah. This brings me back to:

https://m.flickr.com/#/photos/johnhallmen/4320502042/in/favorites-nikonboi/

Scroll down a long way to find "Why Summar 12cm f4.5 + Raynox 12 diopter becomes SumRay 50mm f1.9"

This has been lurking in the back of my mind for years. I have two copies of the Summar, with the "SumRay" in mind. I seem to have stumbled across an alternative, with AF and no need for bellows.

Interesting!

Harold


Yes, interesting. He says the entrance pupil is not affected. I wonder if that is so. That would not be the case for other situations.



Jan 17, 2017 at 07:03 AM
e6filmuser
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p.1 #14 · p.1 #14 · Trichia decipiens Fruiting Bodies


Archibald wrote:
Yes, interesting. He says the entrance pupil is not affected. I wonder if that is so. That would not be the case for other situations.


He published it, where I first saw it, in a blog where the owner is professionally red hot on photography optics and it would have had to be correct.

harold



Jan 17, 2017 at 09:08 AM
Archibald
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p.1 #15 · p.1 #15 · Trichia decipiens Fruiting Bodies


I had a look at a couple of my Canon lenses with and without the Canon 500D closeup lens. Just from peering in the front, the entrance pupil appears to increase with the supplementary lens when using my Canon 100mm and 55-250mm lenses (the 55-250 at 250mm). The increase with the 100mm is marginal. It is hard to judge, though, and maybe I'm not determining the property correctly. I'm thinking that once everything has been taken into account, that the increase might be quite small.

At any rate, even if we assume no change in the entrance pupil, the shortening of the focal length will give the combo a lower f number.

The upshot is that when using a closeup lens, the effective aperture becomes bigger. So one should stop down more for equivalent DOF and diffraction.



Jan 17, 2017 at 05:10 PM
e6filmuser
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p.1 #16 · p.1 #16 · Trichia decipiens Fruiting Bodies


Archibald wrote:
I had a look at a couple of my Canon lenses with and without the Canon 500D closeup lens. Just from peering in the front, the entrance pupil appears to increase with the supplementary lens when using my Canon 100mm and 55-250mm lenses (the 55-250 at 250mm). The increase with the 100mm is marginal. It is hard to judge, though, and maybe I'm not determining the property correctly. I'm thinking that once everything has been taken into account, that the increase might be quite small.

At any rate, even if we assume no change in the entrance pupil, the shortening of
...Show more

Thanks. I'm happy to let you work with those issues. When it comes to a given shot, I work empirically, adjusting the aperture to get an appropriate DOF in the viewfinder. A numerical value of some sort is a useful reference:

a) To inform the viewers of the final image
b) For me to reproduce or alter the DOF in future images

Any small diffraction effect can be dealt with by PP software.

If an effect such as you suggest exists when using the Raynox in a given situation, there is nothing I can do about it. Awareness of it is something I can take into account when my chosen aperture seems not to give the DOF I expected.

It remains to be seen whether the MSN-202 is the best tool I have for photographing less-static subjects and/or larger ones. In macro in general, I like to give myself plenty of working distance, which some of my other lenses can offer but at the loss of full aperture framing and focusing.

Harold



Jan 17, 2017 at 06:39 PM







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