5x with a budget rail and tripod?

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Chris C
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5x with a budget rail and tripod?

Post by Chris C »

Hi,

Thanks for allowing me into this forum, this is my first post here.

I currently use a Laowa 65mm 2x macro lens mounted on a canon m50 crop camera for macro images. Mostly I take my pictures handheld, but I've also done some stacks using a cheap manual rail and tripod. With 2x magnification and about 80um steps, stacking works well with this setup and I believe the cheapness of the rail and tripod do not really hamper the photo quality.

I would be cool to be able to do higher magnification images. I don't believe 10x or higher is possible without significantly upgrading more or less every aspect of my setup. But I figured 4x or 5x magnification at .12 to .15 NA could work with 30um step size on my rail and would resolve more details than I currently can. Probably the best way to achieve this would be to get a Laowa 25mm 5x with EFM adapter, but preferably I'd go for a cheaper option that's more in line with the rest of my setup.
There are some relatively inexpense microscope objectives that I could mount with some adapters onto the 55-200mm EFM telezoom I already have, like e.g. the one sold by wemacro. But I'm not sure if this is the right way to go to get more detailed images than crops of my 2x photo's. The point is of course not to only to have more work in stacking, but also to have a resulting image that is noticeably more detailed. Can anyone here make some recommendations? Is this a good way to go, and what would be a suitable objective?

Thanks!

lothman
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Re: 5x with a budget rail and tripod?

Post by lothman »

the Amscope 4x is a cheap and good point to start with. Have a look at Roberts review:

http://www.photomacrography.net/forum/v ... hp?t=36028
https://www.closeuphotography.com/seven ... -objective

If you have a bellows available or a tube set, you can find cheap adapters (RMS->M42) to mount the lens.

Chris S.
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Re: 5x with a budget rail and tripod?

Post by Chris S. »

Chris C, welcome aboard! :D

A 4x or 5x objective will not only be cheaper than the Laowa 25mm 5x, but also, at 4x or 5x, the objective is likely to be the better performer.

Lothman's points were well-taken if you want to use finite objectives, which mount on tubes or bellows of empty air. The WeMacro 5x you mentioned--an infinite objective designed for mounting on another lens focused at infinity--is likely a decent option for use on your zoom. (You will want to use your zoom at, or close to, its 200mm end to avoid getting dark corners)

If you have any confusion about the difference between finite and infinite objectives, or how to mount them in your setup, you might check out FAQ: How can I hook a microscope objective to my camera?

--Chris S.

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Scarodactyl
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Re: 5x with a budget rail and tripod?

Post by Scarodactyl »

I am not sure anyone has been able to replicate those good results after that batch of amscope objectives sold out. Amscope sources from multiple vendors and there are at least two basic designs that are put in near-identical shells, and even ones which look like they're the same design undernesth don't always perform well.

joshmacro
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Re: 5x with a budget rail and tripod?

Post by joshmacro »

Chris C - If you are doing studio work then invest in a good bellows (like a Canon Auto Bellows) and either a ~4x microscope objective (as mentioned in this thread) or enlarger lens (like the El-Nikkor 50mm F/2.8 N) to start with. I think starting off with an enlarger lens is better but that's just me. With a good bellows that allows the rear of the bellows to move you can use rear stepping and do not need to worry about a precision rail. The bellows and lens should be around $150. The solution would be different if you are doing work in the field.

Chris C
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Re: 5x with a budget rail and tripod?

Post by Chris C »

Thanks all for the useful answers. I never believed an objective under $20 could give decent image quality. So indeed using a microscope objective is probably the best way to go. I'm somewhat worried though that the resolution improvements that can be obtained with a 0.10 NA objective would be somewhat underwhelming when compared to my current 2x lens. See below image for a 100% crop I made with the 2x lens at f/4.

When using NA = M / (2*f *(M+1)) with M=2 and f=4 to estimate the NA, I find an NA of 0.083 which is pretty close to 0.10. This leads me to believe that the gain in sharpness of a 0.10 NA objective might be pretty small, and I'll mostly get an increase in magnification. With an NA closer to 0.15, I'd expect much better resolution. Does my reasoning make sense here, or are these fixed magnification objectives simply better optical performers?

What would be the benefit of getting an auto bellows vs using a rail? These bellows systems seem to be difficult to come by for my mount, and also generally a bit less common than rails. Indeed I'm not looking for a system to use in the field.
stack_crop.jpg
Edit: Originally, an outdated NA equation was used: NA = M / sqrt(4*f^2 *(M+1)^2 + M ^2), which is now corrected so future readers will use the correct equation.
Last edited by Chris C on Mon Oct 03, 2022 12:32 am, edited 1 time in total.

lothman
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Re: 5x with a budget rail and tripod?

Post by lothman »

this is a stack of a silicon waver with finest details I made with a LOMO 3,7x at Sony A7r4 Full frame before I sold it here in the forum.
http://www.lolux.de/Lothar/For_Igor.jpg
you can see that such a lens even at full frame offers sharp edges.

I'm not sure what you mean with "auto bellows". Usually this is meant for a bellows which can transmit aperture from the lens to the camera. With a microscope lens such a feature would be useless since microscope lenses usually have no aperture to be set and if so, then manually. An automated rail would offer you more comfort when taking the image stack but until 5x this can be done by hand.

rjlittlefield
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Re: 5x with a budget rail and tripod?

Post by rjlittlefield »

Chris C wrote:
Wed Sep 28, 2022 12:46 am
I'm somewhat worried though that the resolution improvements that can be obtained with a 0.10 NA objective would be somewhat underwhelming when compared to my current 2x lens.
...
When using NA = M / sqrt(4*f^2 *(M+1)^2 + M ^2) with M=2 and f=4 to estimate the NA, I find an NA of 0.083 which is pretty close to 0.10. This leads me to believe that the gain in sharpness of a 0.10 NA objective might be pretty small, and I'll mostly get an increase in magnification. With an NA closer to 0.15, I'd expect much better resolution. Does my reasoning make sense here, or are these fixed magnification objectives simply better optical performers?
Your reasoning is generally sound. Inexpensive microscope objectives at NA 0.10 would offer little improvement over your current setup.

I notice that the formula you're using for NA is oddly complicated and is not strictly correct, though in this case it does produce quite close to the correct number. The correct formula, for a lens with pupil factor 1, is simply that NA = M / (2*f*(M+1)) . Your formula would reduce to that, except for the additional term of M^2 inside the sqrt, which is so small in comparison to the other term that it makes essentially no difference. The correct formula calculates 0.083333; yours gives 0.083045.

But I am curious: where did your formula come from?

--Rik

Chris C
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Re: 5x with a budget rail and tripod?

Post by Chris C »

lothman wrote:
Wed Sep 28, 2022 4:25 am
this is a stack of a silicon waver with finest details I made with a LOMO 3,7x at Sony A7r4 Full frame before I sold it here in the forum.
http://www.lolux.de/Lothar/For_Igor.jpg
you can see that such a lens even at full frame offers sharp edges.

I'm not sure what you mean with "auto bellows". Usually this is meant for a bellows which can transmit aperture from the lens to the camera. With a microscope lens such a feature would be useless since microscope lenses usually have no aperture to be set and if so, then manually. An automated rail would offer you more comfort when taking the image stack but until 5x this can be done by hand.
Thanks for the sample image! The "auto bellows" were suggested by joshmacro in response to the question in my topic opening. I'm still not quite sure what the major benefit of this would be.

rjlittlefield wrote:
Wed Sep 28, 2022 9:51 am
Your reasoning is generally sound. Inexpensive microscope objectives at NA 0.10 would offer little improvement over your current setup.

I notice that the formula you're using for NA is oddly complicated and is not strictly correct, though in this case it does produce quite close to the correct number. The correct formula, for a lens with pupil factor 1, is simply that NA = M / (2*f*(M+1)) . Your formula would reduce to that, except for the additional term of M^2 inside the sqrt, which is so small in comparison to the other term that it makes essentially no difference. The correct formula calculates 0.083333; yours gives 0.083045.

But I am curious: where did your formula come from?

--Rik
Thanks for your clear reply! I'll be on the lookout for an affordable higher NA objective then. They all seem to be quite a bit more expensive though.

The equation I found on this forum:
rjlittlefield wrote:
Wed Feb 21, 2007 11:54 pm
NA = M / square root (4 f squared (M+1)squared + M squared)
This appears to be the exact formula for a thin lens approximation, where f = focal length / aperture diameter, that is, the lens's f-number not corrected for magnification.
...
--Rik

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Re: 5x with a budget rail and tripod?

Post by rjlittlefield »

Chris C wrote:
Thu Sep 29, 2022 6:56 am
The equation I found on this forum:
rjlittlefield wrote:
Wed Feb 21, 2007 11:54 pm
NA = M / square root (4 f squared (M+1)squared + M squared)
This appears to be the exact formula for a thin lens approximation, where f = focal length / aperture diameter, that is, the lens's f-number not corrected for magnification.
...
--Rik
Thanks for the source!

First, let me congratulate you on finding that 15-year old thread at https://www.photomacrography.net/forum/ ... f=8&t=1856 . I suppose it turned up in some search.

I have reviewed that thread, and I believe that it correctly reflects technical understanding at the time it was written.

Unfortunately that understanding was not quite right, as explained in detail at https://www.photomacrography.net/forum/ ... 11#p196511 and the links therein to https://www.photomacrography.net/forum/ ... 4964#44964 .

So, this is the rare situation where you should forget the complicated formula and remember only the simple one.

--Rik

joshmacro
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Re: 5x with a budget rail and tripod?

Post by joshmacro »

Chris C wrote:
Thu Sep 29, 2022 6:56 am
Thanks for the sample image! The "auto bellows" were suggested by joshmacro in response to the question in my topic opening. I'm still not quite sure what the major benefit of this would be.
Chris - the "auto bellows" I referred to are not automatic. That's just the name. Good bellows to get are Canon FD Bellows and Olympus OM Bellows. Good bellows have three knobs: One that moves the entire bellows back and forth; One that moves the front bellows element back and forth; One that moves the rear bellows element back and forth. Not all bellows have a rear element that moves back and forth so I would avoid those. The benefit of a good bellows is what I mention below: "With a good bellows that allows the rear of the bellows to move you can use rear stepping and do not need to worry about a precision rail." Rear stepping is moving the rear element of the bellows closer to the subject for each frame of the focus stack rather than moving the entire bellows closer to the subject. Rear stepping allows longer turns of the bellows knobs and is easy to achieve with magnifications of at least up to 5x.

Chris C
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Re: 5x with a budget rail and tripod?

Post by Chris C »

joshmacro wrote:
Thu Sep 29, 2022 5:26 pm
Chris C wrote:
Thu Sep 29, 2022 6:56 am
Thanks for the sample image! The "auto bellows" were suggested by joshmacro in response to the question in my topic opening. I'm still not quite sure what the major benefit of this would be.
Chris - the "auto bellows" I referred to are not automatic. That's just the name. Good bellows to get are Canon FD Bellows and Olympus OM Bellows. Good bellows have three knobs: One that moves the entire bellows back and forth; One that moves the front bellows element back and forth; One that moves the rear bellows element back and forth. Not all bellows have a rear element that moves back and forth so I would avoid those. The benefit of a good bellows is what I mention below: "With a good bellows that allows the rear of the bellows to move you can use rear stepping and do not need to worry about a precision rail." Rear stepping is moving the rear element of the bellows closer to the subject for each frame of the focus stack rather than moving the entire bellows closer to the subject. Rear stepping allows longer turns of the bellows knobs and is easy to achieve with magnifications of at least up to 5x.
Thanks for clarifying! If I understand correctly now, the benefit of using such bellows would be that you can make the adjustments at the image side. When using 5x magnification, the adjustments at the image side are 5x bigger than at the object side and therefore much easier to do manually. This would require a setup that actually uses such bellows, so e.g. a finite objective on an empty tube with bellows or a reverse mounted lens on bellows as you suggested. When using a 5x lens or putting a 5x infinite objective to the front of my 200mm lens there would be no place for such bellows, right?

rjlittlefield wrote:
Thu Sep 29, 2022 3:08 pm

Thanks for the source!

First, let me congratulate you on finding that 15-year old thread at https://www.photomacrography.net/forum/ ... f=8&t=1856 . I suppose it turned up in some search.

I have reviewed that thread, and I believe that it correctly reflects technical understanding at the time it was written.

Unfortunately that understanding was not quite right, as explained in detail at https://www.photomacrography.net/forum/ ... 11#p196511 and the links therein to https://www.photomacrography.net/forum/ ... 4964#44964 .

So, this is the rare situation where you should forget the complicated formula and remember only the simple one.
Thanks for the elaborate clarification! I edited my original post a bit to prevent that someone will repeat my mistake in 15 years time.

rjlittlefield
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Re: 5x with a budget rail and tripod?

Post by rjlittlefield »

Chris C wrote:
Mon Oct 03, 2022 12:47 am
joshmacro wrote:
Thu Sep 29, 2022 5:26 pm
"With a good bellows that allows the rear of the bellows to move you can use rear stepping and do not need to worry about a precision rail." Rear stepping is moving the rear element of the bellows closer to the subject for each frame of the focus stack rather than moving the entire bellows closer to the subject. Rear stepping allows longer turns of the bellows knobs and is easy to achieve with magnifications of at least up to 5x.
Thanks for clarifying! If I understand correctly now, the benefit of using such bellows would be that you can make the adjustments at the image side. When using 5x magnification, the adjustments at the image side are 5x bigger than at the object side and therefore much easier to do manually
An important correction: rear steps are larger than front steps by a factor of magnification squared. So, at 5X magnification, image-side steps are 25 times larger than object-side steps.

There are several ways to look at this.

One of them is that optical magnification stretches the aspect ratio of the image, as well as making it larger laterally. The stretching factor is equal to the magnification factor, so combining the factors gives magnification squared along the optical axis.

Another way, very helpful for thinking about diffraction, is that image-side steps are determined entirely by the effective f-number on the image side. Using the usual criterion of 1/4-lambda wavefront error for green light with lambda=550 nm, this means that effective f/20 can use an image-side step of 0.88 mm, independent of magnification.

There are tradeoffs in using rear bellows focusing. At low magnification it works wonderfully, with the additional benefit that because the lens entrance pupil does not move, there are no changes in perspective that can degrade the stacked result. However, at higher magnification you'll find that rear bellows focusing introduces changes in magnification and image brightness that can limit the usable stack depth to be less than you might like. Depending on personal preferences it may still work well at 5X, but looking forward, do not expect rear bellows focusing to scale well to higher magnifications.

--Rik

joshmacro
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Re: 5x with a budget rail and tripod?

Post by joshmacro »

rjlittlefield wrote:
Mon Oct 03, 2022 10:31 am
There are tradeoffs in using rear bellows focusing. At low magnification it works wonderfully, with the additional benefit that because the lens entrance pupil does not move, there are no changes in perspective that can degrade the stacked result. However, at higher magnification you'll find that rear bellows focusing introduces changes in magnification and image brightness that can limit the usable stack depth to be less than you might like. Depending on personal preferences it may still work well at 5X, but looking forward, do not expect rear bellows focusing to scale well to higher magnifications.
In practice I have found that rear bellows focusing works fine in the 4-5x range. If there are any tests or comparisons out there it would be great to see. I have also tried closer to and at 10x and it presents problems as Rik mentions.

Chris C: This post also may be of interest:
https://www.photomacrography.net/forum/ ... 25&t=42661

Chris C
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Re: 5x with a budget rail and tripod?

Post by Chris C »

Af
joshmacro wrote:
Mon Oct 03, 2022 2:27 pm
Chris C: This post also may be of interest:
https://www.photomacrography.net/forum/ ... 25&t=42661
Thanks for linking to this!! If I understand correctly, using the rear bellows would enable 25x larger step size at 5x magnification.
I expect that for my particular case though, it then makes no net difference. My rail gives a 1mm step per rotation and the bellows a 25mm step according to the linked post, which is again a 25x ratio. This exactly cancels the advantage of the bellows, so with my rail I would be similarly capable of doing the necessary small steps in focus.

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