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Review of Canon 10x32 IS

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Old Monday 25th February 2019, 14:47   #51
henry link
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David, I'll just add one more source to roof prism lines showing up in star-tests of binoculars at boosted magnifications. If the booster has a roof prism it may appear as a shadow line running through the outside of focus pattern (see the example on the left below). For some reason it appears to be more of a problem when photographing star tests than visually. Other distortions of the diffraction patterns can come from dust and oil droplets on the eyelens of the binocular and floaters in the eye.

You probably noticed that I mentioned in the old 8x54 FL review that its image at 8x seemed to be worse than it ought to be from examining its stopped down high magnification star test. I speculated then that excessive lateral color near the field center (which doesn't show up well or at all in a high magnification star-test) was the possible culprit, just like the Canon 10x32 now.

Kimmo, If you're considering the Hubble Optics artificial star, I have one now and have found a few problems with it. Firstly, it comes with a plastic diffusing disk between the LED bulbs and the metal disk with the pinholes, which dims the star points considerably. It's just bright enough for visual use in low light, but photography requires very long exposures at my camera's highest ISO setting of 1600. Removing the diffuser helps, but it's still not very bright.

The other problem is that the LEDs have a strong blue/violet bias, which causes any blue/violet component in CA or spherochromatism to be highly exaggerated, like the blue spot in the defocused photo of the five pinholes made through the 10x32 below.

Wolf Beam, if the lateral color in the Canon eventually disappears for you, I think you'll never have to worry about CA in any binocular again.

Henry
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Last edited by henry link : Monday 25th February 2019 at 14:55.
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Old Monday 25th February 2019, 17:29   #52
typo
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Henry,

Thanks for the warning.

Just from appearances, I put the effective resolution of that first HT 8x54 I tried between 170 and 190/D. From what I saw of the Zeiss stopped down MTF, it appeared their test sample was at the top end of that range. I suspect there might have been a bit more than a little bit of CA and SA going on, but they certainly weren't going to spill the beans.

David
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Old Monday 25th February 2019, 21:24   #53
kabsetz
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Henry,

Thanks for the comments on the Hubble Optics artificial star. You have saved me some trouble and a little bit of money. I may look into a fibre optics solution with a halogen light source instead.

There's one more test I'd like you to conduct with the 10x32 IS: low light detail or resolving power. Not that we use binoculars that much for terrestrial viewing in dusk or twilight or, indeed, night time, but it is another area where I've found IS to be very effective, and it is also an area where a small exit pupil is a decided disadvantage.

Kimmo
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Old Tuesday 26th February 2019, 08:30   #54
typo
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Henry, Kimmo,

Looks like the target I made for indoor use was was about 0.1mm or 5-6" at 4m which is probably not good enough, even for stopped down testing. The ballbearing I've used as a glitter point should have been OK though. I have one binocular that has always given me quite distorted patterns in one barrel at full aperture and almost absent inner rings stopped down, yet still manages a respectable 126/D and seemingly a better than average contrast profile. The other barrel seems to gives something much closer to the standard pattern, yet only 136/D and just slightly worse contrast. The I'll give it another go when I can.

David
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Old Tuesday 26th February 2019, 16:20   #55
henry link
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David,

How large are the exit pupils in your tests? In my experience with boosted binoculars the airy disc at best focus and defocused between 2 and 5 rings is much easier to evaluate with a 0.5mm exit pupil.

Henry
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Old Tuesday 26th February 2019, 19:32   #56
typo
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Sorry Henry, what is the value of doing that? The pupil of the eye cannot contract to 0.5mm.

I had a another look at chapter 1 of Suiter's book and now realise I had made a fundamental error in expecting to see the classic pattern of rings to be revealed as the effective resolution approached the diffraction limit. I now realise I should have expected the opposite.

This is how Suiter produced his reference pattern. Fig. 1-5
"The contrast of the pattern has been increased by using one very pure red light from a helium-neon laser reflected in a small reflective sphere. A hole punched in metal and placed over a small refractor created the aperture."

The critical thing there is monochromatic light. This is how he describes the result of using a white light source.
"Each contributing color exhibits a different number of rings in its expanded disk. The minima of one color sit on top of maxima of another color, and the net effect is largely to wash out any variation of the interior of the disk."

That pretty much describes what I saw through the left barrel in #54 and noted testing other binoculars with even higher effective resolutions. I had assumed they were flawed results as they contrasted with many I'd seen here. They may have been excellent results, but I'd need to follow Suiter's check list to be sure. It now leaves me wondering what might have been the nature of the defect was that produced the misleadingly 'normal' pattern in the right barrel #54?

Unfortunately it isn't always obvious if Suiter's illustrations were produced by monochromatic or polychromatic light. As you said, coloured illustrations would have been enormously helpful. I'll need scrutinise things more carefully.

David
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