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 Replies: 8 / Views: 1,994 |
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Pillar of the Community
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4132 Posts |
Just got this (and necessary adapters) off of ebay:   Cheapo Nikon 4x/0.1 Objective by CaptainFwiffo, on Flickr The listing described it as a Nikon Brightfield KHC Series. With a cone RMS-M42 adapter, I end up having almost exactly the right amount of extension with my bellows at minimum, which will make it easy to use 160mm tube length objectives (which actually need 150mm of total extension because 160 includes space for a telescope eyepiece). Unfortunately, this particular objective has an very small usable image circle. It's also got a lot of chromatic aberration, so I assume it was intended for a microscope that corrects for that in the eyepiece.  Cheapo Nikon 4x/0.1 Obj. Stack Test by CaptainFwiffo, on Flickr  Center Crop by CaptainFwiffo, on Flickr  Mintmark Crop by CaptainFwiffo, on Flickr It does have some resolution in the center of the image. I tried increasing the magnification to see if I could use just the middle of the image circle, but for some reason it didn't seem to help the vignetting at all? At least my Lego rig is still holding up. I've got a couple of the Cnscope objectives on the way, so hopefully those will do better. |
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Pillar of the Community
 United States
4038 Posts |
Increasing magnification should eliminate vignetting if it's the objective causing the problem. The vignetting must be happening between the objective and the sensor. That will also mess up resolution due to diffraction. None of the objectives I own vignette at anywhere near rated magnification, and most can go to half or less and still do OK. Might you have something in the system that is causing the vignetting? I suppose there could be something very wrong with the objective but I am not sure what it could be that increasing magnification would not change it.
EDIT: I looked through my objectives and found the exact objective you bought....and it also vignettes a bit at rated mag. The Nikon 4 Plan that I usually use doesn't vignette at all even at 2x, so this "4 0.1" Nikon seems to have an issue. I'll take a pic with it and post the result.
Edited by rmpsrpms
01/11/2013 10:35 am
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Pillar of the Community
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4132 Posts |
I think it must be the objective, because there isn't anything else in the light path, as far as I can tell. The components are:
Camera
EF-M42 adapter
14mm M42 tube
Bellows
M42-RMS Cone Adapter
Objective
I've never had vignetting like this before from this setup with other lenses. I don't know why it didn't seem to improve with additional magnification either, that doesn't make sense. I'm going to give it another try with more extension, maybe I was seeing things. But if it has to be used at like 6-8x to fill the sensor with a quality image, 0.1 NA is too low for a sharp image and I'd be better off with a different objective.
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Pillar of the Community
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4038 Posts |
I set up the objective with 160mm tube length (not 150, but doesn't make a huge difference) and shot a stack on my 56-D test coin. I'm seeing vignetting but not as dramatic as you show above. Here is the overall shot and the detail around the mintmark:   So I agree, this objective is not the best. It should not vignette at all at its rated magnification...Ray Edited by rmpsrpms
01/11/2013 11:40 am
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Pillar of the Community
United States
4038 Posts |
BTW, for folks interested in figuring out the nomenclature on objectives, here is a good link that explains Nikon's approach. Other manufacturers are similar, though that "LPL" objective is an odd one. On the Nikon page they do say that an "L" indicates long working distance, hence my assumption that LPL means LWD Plan. Anyway, here is the link: http://www.microscopyu.com/articles...vespecs.htmlContact me for photographic equipment or visit my home page at: http://macrocoins.com |
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Pillar of the Community
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4132 Posts |
The Cnscope seller did say that the LPL stood for LWD plan - 16.5mm working distance. The metallurgical one was also 16.5mm working distance, so I'm not sure what the real difference is. They are a different shape and the LPL one is few dollars more expensive, so there is something different about the two... The metallurgical one seems to be better shaped for lighting based on the pictures.
I ordered both the metallurgical 4x/0.1 and the cheapest achromat 4x/0.1 (only $19.99 and free shipping!), so I'll do a mini-shoot-out when I get them. Posts on photomacrography.net suggest they may be decent performers, and if so, they would be an easily available, el-cheapo, "known quantity" option.
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Pillar of the Community
United States
4132 Posts |
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Pillar of the Community
United States
4038 Posts |
Is the first image the full frame or a crop? If full frame, then that is quite a lot of magnification, maybe around 10x? Way beyond what that lens is optimized for with NA of 0.1.
I found a second example of the objective in my bag of tricks and it performs about the same as the earlier one, with only a small amount of vignetting compared with your example. I think you got a bum copy, and I apologize for recommending the objective in the first place. Luckily it was not too expensive.
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Pillar of the Community
United States
4132 Posts |
Yeah, that's the full frame. That's how much I had to extend it to eliminate the vignetting. I could probably do an in-between position and eliminate the vignetting in the raw processor, but the image quality still would be poor.
Don't worry about the recommendation - you're always taking a chance when you get an optic that cheap, and I just wanted something to experiment with.
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Replies: 8 / Views: 1,994 |
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Posted 01/11/2013 10:57 am
