Some more questions from a rank amateur

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tevans9129
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Some more questions from a rank amateur

Post by tevans9129 »

Using a Nikon D800e, PB-6 bellows and an old 20mm f/2.8 lens reversed, and if, my calculations are close, 6X with bellows closed and 9X with bellows fully extended…would image quality be better with something like the Amscope 4X, 10X? At this point in time, I am not sure that I would be capable of using more than 10X. All opinions/suggestions are much appreciated. Cost is a factor.

Ted

ChrisR
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Post by ChrisR »

No answer...

My answer, "I don't know" :D

But it should be better. At 10x, even at full aperture, you're very much affected by diffraction. Not accounting for it being a retrofocus lens (which makes things a bit worse) your effective aperture is
(10 +1 ) x 2.8 =~f/31
if you have to close the aperture a couple of stops to make the lens do its best, you're at f/62 which means the smallest resolvable dot would cover an awful lot of pixels.

A 10x, NA 0.25 objective, would be effective
10/(2 x NA) = f/20 which is hugely better
We don't see them much in the UK, but I see many at <$50 in the US, so someone will have tried them.

At lower magnifications the math is less against you, but I'd still expect a noticeable difference.
Chris R

tevans9129
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Post by tevans9129 »

ChrisR wrote:No answer...

My answer, "I don't know" :D

But it should be better. At 10x, even at full aperture, you're very much affected by diffraction. Not accounting for it being a retrofocus lens (which makes things a bit worse) your effective aperture is
(10 +1 ) x 2.8 =~f/31
if you have to close the aperture a couple of stops to make the lens do its best, you're at f/62 which means the smallest resolvable dot would cover an awful lot of pixels.

A 10x, NA 0.25 objective, would be effective
10/(2 x NA) = f/20 which is hugely better
We don't see them much in the UK, but I see many at <$50 in the US, so someone will have tried them.

At lower magnifications the math is less against you, but I'd still expect a noticeable difference.
I very much appreciate your response CR. Being totally ignorant about microscope objective lens, it is confusing to me as to what components I would need to connect one to my bellows. Any suggestions for what would be needed for the connection? I have been reading on the subject but unfortunately, I am a slow learner. :(

tevans9129
Posts: 129
Joined: Thu Nov 30, 2017 8:03 am
Location: TN

Post by tevans9129 »

I have been looking at the objectives at the link below for a starting point using microscope objectives lens. Is this a reasonable path or should I look at something different? If, these are OK, what components will I need to connect to a Nikon PB-6 bellows? Thanks.

https://www.amazon.com/AmScope-4X-100X- ... C6SFKV00JN
Last edited by tevans9129 on Mon Dec 04, 2017 4:45 pm, edited 1 time in total.

mawyatt
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Post by mawyatt »

This is a very inexpensive finite objective that works well around 4X.

http://www.amscope.com/accessories/obje ... ens-1.html

Originally found by Robert OToole.

https://www.closeuphotography.com/seven ... objective/

https://www.closeuphotography.com/generic-objectives

You just need an RMS adapter and maybe an adapter for the PB6 bellows. To change magnification just change the bellows to adjust the lens to camera sensor distance, which is 160mm nominal for ~4X.

Another, but infinite object rather than finite objective, is the WeMacro 4X. This lens requires a tube lens of nominal 180mm for 4X, but works well with an old Nikon 200mm F4 "Q" (eBay for <$50) as a tube lens. This setup is a little more complex because of the extra "tube" lens, and changing magnification is more difficult because you much change the "tube" lens.

http://www.wemacro.com/?product=4x-infi ... ctive-lens


Best,

Mike

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Post by Deanimator »

mawyatt wrote:This is a very inexpensive finite objective that works well around 4X.

http://www.amscope.com/accessories/obje ... ens-1.html

Originally found by Robert OToole.

https://www.closeuphotography.com/seven ... objective/

https://www.closeuphotography.com/generic-objectives

You just need an RMS adapter and maybe an adapter for the PB6 bellows. To change magnification just change the bellows to adjust the lens to camera sensor distance, which is 160mm nominal for ~4X.
Let me heartily endorse this choice for a beginner on a budget.

I started using one a few weeks ago and have been extremely happy with it, especially for the investment required.

I've used mine both with tubes and with a bellows. I haven't settled on a method of killing reflection in the tubes, so I mostly use the bellows, which I think are a superior solution. I bought the tubes as a backup in case there were issues with the bellows.

I've got a 10x coming Wednesday. It was about twice as expensive as the 4x. It's cheap enough to take a chance on.

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Post by Pau »

tevans9129 wrote:I have been looking at the objectives at the link below for a starting point using microscope objectives lens. Is this a reasonable path or should I look at something different? If, these are OK, what components will I need to connect to a Nikon PB-6 bellows? Thanks.

https://www.amazon.com/AmScope-4X-100X- ... C6SFKV00JN
Don't buy this set, they are entry level achromats intended for school grade microscopes (not bad for this application). The 40X and 100X oil wont have any utility for macro.
The 4X Plan referenced seems an excellent option.
Pau

mawyatt
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Post by mawyatt »

Deanimator wrote:
mawyatt wrote:This is a very inexpensive finite objective that works well around 4X.

http://www.amscope.com/accessories/obje ... ens-1.html

Originally found by Robert OToole.

https://www.closeuphotography.com/seven ... objective/

https://www.closeuphotography.com/generic-objectives

You just need an RMS adapter and maybe an adapter for the PB6 bellows. To change magnification just change the bellows to adjust the lens to camera sensor distance, which is 160mm nominal for ~4X.
Let me heartily endorse this choice for a beginner on a budget.

I started using one a few weeks ago and have been extremely happy with it, especially for the investment required.

I've used mine both with tubes and with a bellows. I haven't settled on a method of killing reflection in the tubes, so I mostly use the bellows, which I think are a superior solution. I bought the tubes as a backup in case there were issues with the bellows.

I've got a 10x coming Wednesday. It was about twice as expensive as the 4x. It's cheap enough to take a chance on.
Let us know how the AmScope 10X behaves, I suspect it's not going to be the jewel the 4X is....but we might get lucky again :D

On APC/DX sensors you can just roll up a tube of Protostar or 1898 Beetle Black card stock to help squash internal reflections in the M42mm extension tubes. This might not work on full frame sensors, which is why I went with M52mm tubes long ago with more interior diameter to work with for flocking without interfering with the optical path. Evidently these 52mm tubes are difficult to find, and expensive on eBay. I've used these (See below for Nikon) in place of the 52mm tubes with the appropriate adapters. They are about 60mm diameter and very easy to flock. Get a few extra sets to make up a really tight fitting extension tube set. I use these on my permanent extension setups like with the Raynox 150 & 250 tube lenses and for the PN105 extension.

https://www.ebay.com/itm/Macro-Extensio ... xyP4dTdJoE
Best,

Mike

tevans9129
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Post by tevans9129 »

Many thanks to all for the comments, they were very helpful...I have ordered the Amscope 4x and 10x to begin with. Ted
Last edited by tevans9129 on Tue Dec 05, 2017 1:19 pm, edited 1 time in total.

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Post by Deanimator »

mawyatt wrote:Let us know how the AmScope 10X behaves, I suspect it's not going to be the jewel the 4X is....but we might get lucky again :D
I figured for as cheap as it was, it was worth a try.
mawyatt wrote:On APC/DX sensors you can just roll up a tube of Protostar or 1898 Beetle Black card stock to help squash internal reflections in the M42mm extension tubes. This might not work on full frame sensors, which is why I went with M52mm tubes long ago with more interior diameter to work with for flocking without interfering with the optical path. Evidently these 52mm tubes are difficult to find, and expensive on eBay. I've used these (See below for Nikon) in place of the 52mm tubes with the appropriate adapters. They are about 60mm diameter and very easy to flock. Get a few extra sets to make up a really tight fitting extension tube set. I use these on my permanent extension setups like with the Raynox 150 & 250 tube lenses and for the PN105 extension.

https://www.ebay.com/itm/Macro-Extensio ... xyP4dTdJoE
Best,

Mike
I've got some flat black spray paint which I used when making a lens hood for my 500mm mirror lenses. I may give that a try.

I've got a very similar set of manual extension tubes which I bought when I was first getting started in macro. They worked, albeit with the expected limitations. I later bought a set of automated tubes, which were a good combination with my Tokina 100mm macro lens. Lately, I've combined the two sets of tubes with my Minolta 50mm manual reversed onto them. I got quite respectable results at a about 3.5x.

mawyatt
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Post by mawyatt »

Long ago I tried the flat black spray paint, couple types, and results were not as good as flocking material like Protostar. With the flat paint you could easily see a reflection inside a long tube set when looking at an off-angle bright source. The reflection was much less noticeable with Protostar and the Beetle Black card stock is even better, almost no reflection at any angle. Think someone (Charles, Rik or Lou maybe) did a simple test awhile back and showed the Protostar and Beetle Black results.

mawyatt
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Post by mawyatt »

tevans9129 wrote:Many thanks to all for the comments, they were very helpful...I have ordered the Amscope 4x and 10x to begin with. Ted
Ted,

Let us know how the AmScope 10X works out, the 4X is quite good (I know I've had one since Robert posted about it, and did some chip images with it)...probably the best value for the $ around for an objective.

Best,

Mike

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Post by Deanimator »

mawyatt wrote:Let us know how the AmScope 10X behaves, I suspect it's not going to be the jewel the 4X is....but we might get lucky again :D
I just got my Amscope 10x and it looks very promising.

I haven't even taken an image with it, but through live view, it looks pretty good.

At max extension on the bellows, you can just squeeze 1/16" on a ruler into frame.

I have to get ready for work, but in between, I'm going to try to photograph something with good texture.

For what I paid for it, it seems like a good value.
Last edited by Deanimator on Wed Dec 06, 2017 5:35 pm, edited 1 time in total.

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Post by Deanimator »

I did a stack with the 10x this evening.

The objective seems more than good enough.

The stack however was unusable because the step size was too big.

I'll do some more stacks tomorrow at a smaller step size.

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Post by ChrisR »

The smallest steps you might need with a 10x NA0.25, an APS sensor and 24MP, would be about 7 microns.
Chris R

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