Lens caps or lens adapters for Canon big whites

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JKT
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Lens caps or lens adapters for Canon big whites

Post by JKT »

The old Canon L-series superteles don't have filter threads and don't accept normal lens caps. The new ones might have - I don't know. They do have a groove, which is used to lock the large hood in place instead. So I measured the groove and its surroundings in my FDn 500mm f/4.5 L and designed a lens cap for it. 8)
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It was a very nice fit. It is more difficult to remove than normal lens cap, but it doesn't drop by accident either. This was meant to protect against elements, not impacts and could thus be thinner with the ridges as stiffeners. It shouldn't be too difficult to modify the design to other superteles, IF I had the exact dimensions for them.

It also occurs to me that the same principle could be used to make reversed lens or microscope objective adapter for these lenses. For that I would increase the thickness of the clips and add more rigidity to the front plane ... and naturally leave a hole for gluing a step-down/up adapter. The former would be used with microscope objective and the latter reversed for reversed lenses. I will likely make one for my lens just for fun, but any other lens needs someone to take the measurements ... and the suitability of the adapter would depend on the accuracy of the measurements.

The price for the lens cap was 45€ + shipping from Shapeways. The adapters would likely cost roughly the same ... for this size. Larger ones would be more expensive. I'm afraid the shape doesn't really fit extrusion printing at home.

Any interest or comments?

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Re: Lens caps or lens adapters for Canon big whites

Post by JKT »

Nobody was interested, but it was a fun test. The adapter looks rather similar to the lens cap - a bit thicker and a hole in the middle.
Z_MG_2175.jpg
Z_MG_2174.jpg
The combination would definitely need something like Qioptiq Mag-X for a balanced look. :D
ZIMG_20211217_172855.jpg
The adapter fit perfectly and won't drop or move by accident. If I had dimensions for FDn 300mm f/2.8, the adapter could be easily modified and that would likely be much more relevant as tube lens.

The images are not very good due to many factors, but they do give some idea of the available resolution when combining Nikon Plan Apo 20x/0.75 with 500mm tube lens. The first images is scaled full frame and the second 1:1 crop.
ZNikon 20x & FDn 500 B.jpg
ZNikon 20x & FDn 500 B2.jpg

Adalbert
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Re: Lens caps or lens adapters for Canon big whites

Post by Adalbert »

Hi JKT,
It is a really crazy story about the FDn 500mm f/4.5.
But your mixed lighting-setup is excellent!
Best, ADi

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Re: Lens caps or lens adapters for Canon big whites

Post by JKT »

Thanks Adalbert!

I like it too even though it is not designed for object sizes and working distances needed here. Thus the noise in the images. For butterflies and moths it works much better.

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Re: Lens caps or lens adapters for Canon big whites

Post by dickb »

JKT wrote:
Fri Dec 17, 2021 10:15 am
If I had dimensions for FDn 300mm f/2.8, the adapter could be easily modified and that would likely be much more relevant as tube lens.
I doubt any modification is needed, the FDn 300/2.8 and FDn 500/4.5 share the same lens hood extension (EH 123) that clamps onto the same part as your lens cap /adapter does. I measure the external diameter of the front rubber ring of the FDn 300/2.8 to be 122mm.

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Re: Lens caps or lens adapters for Canon big whites

Post by dickb »

BTW, the Canon 400mm f/2.8 FDn has a similar system for its extension lens hood, with a larger corresponding diameter of about 163mm. So a scaled-up version of your lens cap may work for that as well.

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Re: Lens caps or lens adapters for Canon big whites

Post by JKT »

dickb wrote:
Sun Dec 19, 2021 4:52 am
I doubt any modification is needed, the FDn 300/2.8 and FDn 500/4.5 share the same lens hood extension (EH 123) that clamps onto the same part as your lens cap /adapter does. I measure the external diameter of the front rubber ring of the FDn 300/2.8 to be 122mm.
If the part number is the same, then you are definitely correct. For some reason there is 1 mm difference in outer dimensions for the two lenses in Canon camera museum.
dickb wrote:
Sun Dec 19, 2021 5:48 am
BTW, the Canon 400mm f/2.8 FDn has a similar system for its extension lens hood, with a larger corresponding diameter of about 163mm. So a scaled-up version of your lens cap may work for that as well.
It likely would and the focal length is somewhat more relevant. If mine looked odd, that would be something to see! :D

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Re: Lens caps or lens adapters for Canon big whites

Post by Lou Jost »

Nice work! I found an off-the-shelf set of rings that fits perfectly but passively (no clamps) into the front of the 300mm 2.8. I find that his is good enough for vertical set-ups. I especially like to use these giant lenses on a microscope so all the weight is supported by the the microscope body; only the stage moves (using WeMacro MicroMate).

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Re: Lens caps or lens adapters for Canon big whites

Post by dickb »

JKT wrote:
Sun Dec 19, 2021 6:54 am
dickb wrote:
Sun Dec 19, 2021 4:52 am
I doubt any modification is needed, the FDn 300/2.8 and FDn 500/4.5 share the same lens hood extension (EH 123) that clamps onto the same part as your lens cap /adapter does. I measure the external diameter of the front rubber ring of the FDn 300/2.8 to be 122mm.
If the part number is the same, then you are definitely correct. For some reason there is 1 mm difference in outer dimensions for the two lenses in Canon camera museum.
I don't have a 500/4.5 FDn, so I can't verify its exact diameter. The connection system for the extension lens hood is the same as some of the newer Canon lenses's ones, and consists of a number of fixed lugs on the inside of the extension hood combined with one spring-tensioned variable lug that can be screwed tight. This may well accomodate a millimeter's worth of diameter difference.
JKT wrote:
Sun Dec 19, 2021 6:54 am
dickb wrote:
Sun Dec 19, 2021 5:48 am
BTW, the Canon 400mm f/2.8 FDn has a similar system for its extension lens hood, with a larger corresponding diameter of about 163mm. So a scaled-up version of your lens cap may work for that as well.
It likely would and the focal length is somewhat more relevant. If mine looked odd, that would be something to see! :D
Indeed. My 400/2.8 FDn doesn't have a perfectly round front ring anymore so such an adapter would not fit it unfortunately. With lenses this size and weight the system Lou Jost described somewhere where he rests the reversed lens onto a microscope stand that also holds the specimen holder may work well to keep everything very stable and planparallel. This should be the thread where it was discussed (among many other things)

viewtopic.php?f=25&t=39461&p=247956&hil ... al#p247956

/Edit in the time that it took me to write this Lou himself has already commented on it - oh well, I must be getting very slow

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Re: Lens caps or lens adapters for Canon big whites

Post by Lou Jost »

No Dick, you're quicker than me, you were able to find the thread!

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Re: Lens caps or lens adapters for Canon big whites

Post by Lou Jost »

Here's a picture:
Attachments
_1180363.jpg

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Re: Lens caps or lens adapters for Canon big whites

Post by Lou Jost »

JKT, Rereading this old thread from April
viewtopic.php?p=273237
I see that you already are one step ahead of us, and that you promised:
Maybe I should try the FDn 500mm f/4.5 one day. :D Might be a bit much for vertical StackShot, though.
I guess it wasn't too much after all!

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Re: Lens caps or lens adapters for Canon big whites

Post by JKT »

Lou Jost wrote:
Sun Dec 19, 2021 8:43 am
JKT, Rereading this old thread from April
viewtopic.php?p=273237
I see that you already are one step ahead of us, and that you promised:
Maybe I should try the FDn 500mm f/4.5 one day. :D Might be a bit much for vertical StackShot, though.
I guess it wasn't too much after all!
So it appeared. :D
Unfortunately that objective IS a bit too much for it - especially in this combination. The minimum step is a bit too large.

I had forgotten about the "longer focal length reversed" idea. For that the adapter opening (58mm) may be too small. The step-down I have in now is 58->42, so definitely too small. It might show presence or absence of CA though - even if resolution would be limited. So there might be some value in testing.

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