Author Topic: Dandelion lets me down  (Read 1748 times)

Erik Lund

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Re: Dandelion lets me down
« Reply #15 on: March 21, 2017, 14:48:21 »
No, they are hollow inside the contact block so they can contain the screw springs, similar design as the contact pins of the 'semi-AF' TC-16A just much more vulnerable,,,,
Erik Lund

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Re: Dandelion lets me down
« Reply #16 on: March 21, 2017, 23:11:59 »

An obvious remedy would be to build up more with hard epoxy around the tubes to provide better support around them, but difficult to carry out without getting glue inside the tubes...
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Bjørn Rørslett

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Re: Dandelion lets me down
« Reply #17 on: March 21, 2017, 23:29:33 »
The tubes have to be able to move in- and outwards, so that's not feasible I'd guess.

Jack Dahlgren

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Re: Dandelion lets me down
« Reply #18 on: March 21, 2017, 23:34:13 »
An obvious remedy would be to build up more with hard epoxy around the tubes to provide better support around them, but difficult to carry out without getting glue inside the tubes...

The issue is that with vertical walls on the pins, a sideways load does not translate into an axial force which would depress the pin.

stenrasmussen

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Re: Dandelion lets me down
« Reply #19 on: March 22, 2017, 09:23:55 »
It is my view that the Dandelion is built too fragily. The tiny springs and contact pins are made of ultra thin "brass" and the black housing is made of friable plastic. It works well with very careful handling but cannot stand up to what I deem normal wear and tear.

arthurking83

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Re: Dandelion lets me down
« Reply #20 on: March 24, 2017, 01:56:13 »
.... you could simply register the 50/1.2 lens to the body.  The "unchipped" 50/1.2 will always be correctly recognized as it is without switching between different registrations of more than one MF lenses....

You only get limited metering abilities, the CPU allows more metering functions.


It is my view that the Dandelion is built too fragily. The tiny springs and contact pins are made of ultra thin "brass" and the black housing is made of friable plastic. It works well with very careful handling but cannot stand up to what I deem normal wear and tear.

+1

I had a Dandelion on my 500/8. Firstly the housing started to break away at the leading edge, then the pins at that same leading edge started to shear off.
Lens got stuck on the camera once the entire Dandelion body distorted enough so to remove it, it had to break the flimsy Dandelion body up.
Luckily no damage to the D800.
It was then an ordeal to remove the epoxied reside off the rear filter.
(for those that don't know, the 500/8 uses a rear filter where the Dandelion is glued too. No mods to the lens mount required at all, so it's a good intro into CPU modded manual lenses)

I was always extremely cautious/careful in mounting the 500/8 to the camera too.

FWIW: the main reason I chose the Dandelion for the 500/8, apart from the ease of install, was that the Dandelion allows the camera to set trap focus.
Focusing with the 500/8(or any long manual lens) is difficult as we all know even with a fine grained focus screen(which becomes dark at f/8! :D)
The focus trap experiment worked a treat, and apart from my unstable handholding ability, the images shot with focus trap mode enabled were as sharp as I've ever got with the 500/8 ..

summary: I like the Dandelion CPU for it's ability but will never get another due to the fragility. I also wanted to mod an old 300/2.8 Tamron(adaptall) lens I also have. But will not.

If a solution to the cheaply made Dandelion body can be worked out, I'll definitely consider them again.

ps. the other handy/advantageous property of the Dandelion CPU is the ability to program/reprogram it(via the camera). It's awkward, but doable and a lot more flexible than using the camera body selection for non CPU lenses.
The advantage with this programing system is (for example) you mount a Dandelion to an old extension tube of some kind and use various lenses on that extension tube .. you can obviously set whatever lens factors required for the various lenses.

Looking forward to what Erik can come up with.
Arthur

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Re: Dandelion lets me down
« Reply #21 on: March 24, 2017, 02:31:49 »
The issue is that with vertical walls on the pins, a sideways load does not translate into an axial force which would depress the pin.

I think this comment is right on. I only have one Dandelion, on my BR-2A (the rest of my lenses including PN-11 I modified with Bjørn's chips), and it is always a bit tricky to mount an requires a lot of care both on insertion into the mount and twisting it into place. Even if I built up well with marine epoxy at the rear and the sides, images presented at NG before show that the plastic around the contacts on the front is very thin.

I also wonder about the long term durability of the type of plastic used in Dandelions. Certain plastics like the one used for buckles on my backpacks and bike panniers seem to break down with time (possibly due to UV exposure?), and then they start self destructing one after another (often several within a short time span) with almost no load at all.
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bjornthun

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Re: Dandelion lets me down
« Reply #22 on: March 24, 2017, 02:54:07 »
I think this comment is right on. I only have one Dandelion, on my BR-2A (the rest of my lenses including PN-11 I modified with Bjørn's chips), and it is always a bit tricky to mount an requires a lot of care both on insertion into the mount and twisting it into place. Even if I built up well with marine epoxy at the rear and the sides, images presented at NG before show that the plastic around the contacts on the front is very thin.

I also wonder about the long term durability of the type of plastic used in Dandelions. Certain plastics like the one used for buckles on my backpacks and bike panniers seem to break down with time (possibly due to UV exposure?), and then they start self destructing one after another (often several within a short time span) with almost no load at all.
The BR-2A can also be modified with one of Bjørn R's chips and an AF-S contact block.

Øivind Tøien

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Re: Dandelion lets me down
« Reply #23 on: March 24, 2017, 04:44:03 »
Good to know if the Dandelion breaks, I thought the AFS block would be too deep, but never really checked it.
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Marcus Rowland

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Re: Dandelion lets me down
« Reply #24 on: March 25, 2017, 22:24:41 »
On a related issue (which is what got me to join this forum - someone pointed me here from NikonForums.com); is there anyone making T2 mounts with Nikon AF confirm chips that are actually worth using?

The ones I've seen on eBay look like the chip will break off if you breathe on it. What I want to actually use this for is metering, not AF confirm, with a cheap but reasonably sharp 500mm F8 lens. I've used a round-about route to check that metering ought to work - I also own an Eos body and a focus-confirm M42 adapter, and used the lens on that with an M42 mount. The results were reasonably good for exposure, not wonderful for focus confirmation, but I know that's only supposed to work at f5.6 and below. All of the Nikon mounts on eBay seem to be made or sold by Pixco, but I can't find any reviews or additional information.

Anyone know Pixco, or a good alternative?

arthurking83

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Re: Dandelion lets me down
« Reply #25 on: March 26, 2017, 01:35:10 »
This is how mine started to deteriorate, then fail completely:

The start of the end is nigh:

fatigue on the leading edge corner.

coroners report:

Plastic corner collapsed inwards, and pin to the far right compressed and lost it's ability to return back out.

Once it broke in such a manner, curiosity got the better of me and I had to carefully prise it open to see it's inner workings.
(ie. the shell didn't break in half like this, just the one corner broke and made it easier to prise apart.

I do remember that in prising the shell apart, the plastic did break into smaller fragments rather than come apart in one 'half' piece.
Arthur

Bjørn Rørslett

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Re: Dandelion lets me down
« Reply #26 on: March 26, 2017, 09:57:32 »
Compare this to the "real thing";

robust contact block with sturdy metal guard, bespoke metal screws for mounting instead of glue, silver contact pins with lateral spring action (thus optimised for the situation of putting the lens to the camera)

Need I say more?

Marcus Rowland

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Re: Dandelion lets me down
« Reply #27 on: March 26, 2017, 21:35:43 »
Sounds like I should forget about dandelion chips for the Nikon - the Canon ones seem a lot more robust, but of course the spring contacts etc. are in the body, the chip just has flat contacts. Fortunately it isn't that big a deal, I'm reasonably good at guesstimating exposure with the 500mm lens, or I can use it on my Eos instead.

Are you salvaging contact blocks from Proneas? I see them around cheaply occasionally, it looks like the block is the same.

Bjørn Rørslett

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Re: Dandelion lets me down
« Reply #28 on: March 26, 2017, 22:07:55 »
No, these are factory parts ordered from Nikon.

The Pronea contact blocks were made all in plastic and had an inferior construction compared to the later version. This extends to the build and material of the silver pins as well.

Marcus Rowland

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Re: Dandelion lets me down
« Reply #29 on: March 27, 2017, 00:20:51 »
No, these are factory parts ordered from Nikon.

The Pronea contact blocks were made all in plastic and had an inferior construction compared to the later version. This extends to the build and material of the silver pins as well.

I obviously haven't looked at them closely enough. OK, thanks for your help, I think I'll leave this idea unless someone makes a much better chip.