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Is it possible to get 20-40:1 macro @ home?
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PostPosted: Sun Mar 02, 2014 5:11 am    Post subject: Reply with quote
Does register distance for reverse mounted lens affects anything?

I have some nice RF glass available, so idea is to permanently integrate it into assembly.


PostPosted: Sun Mar 02, 2014 5:22 am    Post subject: Reply with quote
CuriousOne wrote:
Does register distance for reverse mounted lens affects anything?

I have some nice RF glass available, so idea is to permanently integrate it into assembly.


The register distance actually turns out to be your working distance to the subject. This should make sense because if you focus a lens at infinity, it projects the image onto film/sensor plane. Conversely, if you use the lens as a reversed objective focused at infinity, the subject will be at the film/sensor plan working distance. Because of this, there is little penalty paid in working distance to get higher magnification by using shorter lenses. But a corollary to this is you want to use lenses from camera mounts that have the longest register distance in order to have the longest working distance. This will make RF lenses less suitable than SLR lenses.


PostPosted: Mon Mar 03, 2014 5:22 pm    Post subject: Reply with quote
Any problems using CCTV lens for reverse mounting, besides vignetting?


PostPosted: Mon Mar 03, 2014 6:02 pm    Post subject: Reply with quote
CuriousOne wrote:
Any problems using CCTV lens for reverse mounting, besides vignetting?


Short answer, there shouldn't be. I've shot a 15/2.5 Cine Ektar reversed at 29:1, don't recommend it, and a 25/1.9 Cine Ektar II reversed at f/2.8 @ 1:26, recommend it highly.

Question: since the image circle grows with magnification, why are you worried about vignetting?


PostPosted: Mon Mar 03, 2014 8:06 pm    Post subject: Reply with quote
Rarely anyone understands the optics of macro photography, so be gentle Dan! Wink


PostPosted: Mon Mar 03, 2014 8:25 pm    Post subject: Reply with quote
CuriousOne wrote:
Any problems using CCTV lens for reverse mounting, besides vignetting?


Vignetting is more an issue with the tube lens than the objective.


PostPosted: Mon Mar 03, 2014 11:19 pm    Post subject: Reply with quote
Ray Parkhurst wrote:
CuriousOne wrote:
Any problems using CCTV lens for reverse mounting, besides vignetting?


Vignetting is more an issue with the tube lens than the objective.


Tube lens? What tube lens? I used the lenses I mentioned with a single stage of magnification, i.e., at the end of a string of LTM extension tubes filled with air. Special air, of course, that the uninformed will mistakenly take for ordinary air.


PostPosted: Tue Mar 04, 2014 12:08 am    Post subject: Reply with quote
danfromm wrote:
Ray Parkhurst wrote:
CuriousOne wrote:
Any problems using CCTV lens for reverse mounting, besides vignetting?


Vignetting is more an issue with the tube lens than the objective.


Tube lens? What tube lens? I used the lenses I mentioned with a single stage of magnification, i.e., at the end of a string of LTM extension tubes filled with air. Special air, of course, that the uninformed will mistakenly take for ordinary air.


I think the OP is planning to stack the cine lens reversed on his 210mm or 400mm.


PostPosted: Tue Mar 04, 2014 2:46 am    Post subject: Reply with quote
Ray Parkhurst wrote:
danfromm wrote:
Ray Parkhurst wrote:
CuriousOne wrote:
Any problems using CCTV lens for reverse mounting, besides vignetting?


Vignetting is more an issue with the tube lens than the objective.


Tube lens? What tube lens? I used the lenses I mentioned with a single stage of magnification, i.e., at the end of a string of LTM extension tubes filled with air. Special air, of course, that the uninformed will mistakenly take for ordinary air.


I think the OP is planning to stack the cine lens reversed on his 210mm or 400mm.


Interesting if true.

Why on earth would he do that? When we don't use real macro lenses and devices to get extension, we use reversed C-mount lenses and devices to get extension. I first learned about stacking lenses to get the magnification nearly 40 years ago, saw it as something people who had no resources at all did because it was better than nothing.

There's much to be said for inexpensive better than nothing, especially when resources are scarce. But nowadays all the old crap I bought for dimes costs pennies so I can't understand not going for at least second best.

Of course, I am spoiled. I mean, I've had heaps of LTM tubes and adapters for decades.


PostPosted: Tue Mar 04, 2014 3:19 am    Post subject: Reply with quote
danfromm wrote:
Ray Parkhurst wrote:
danfromm wrote:
Ray Parkhurst wrote:
CuriousOne wrote:
Any problems using CCTV lens for reverse mounting, besides vignetting?


Vignetting is more an issue with the tube lens than the objective.


Tube lens? What tube lens? I used the lenses I mentioned with a single stage of magnification, i.e., at the end of a string of LTM extension tubes filled with air. Special air, of course, that the uninformed will mistakenly take for ordinary air.


I think the OP is planning to stack the cine lens reversed on his 210mm or 400mm.


Interesting if true.

Why on earth would he do that? When we don't use real macro lenses and devices to get extension, we use reversed C-mount lenses and devices to get extension. I first learned about stacking lenses to get the magnification nearly 40 years ago, saw it as something people who had no resources at all did because it was better than nothing.

There's much to be said for inexpensive better than nothing, especially when resources are scarce. But nowadays all the old crap I bought for dimes costs pennies so I can't understand not going for at least second best.

Of course, I am spoiled. I mean, I've had heaps of LTM tubes and adapters for decades.


For many objectives, the results with a decent tube lens can be as good or better than using the same objective with extensions. That said, it is not my preference either, but not due to quality concerns. Stacked lenses don't give any flexibility, since the magnifications are fixed ratios. You can use a zoom lens, but most of them don't give the best quality as a tube lens and are tough to keep at a particular zoom setting. For the application the OP is targeting, I still feel the best method is a good long working distance, finite microscope objective on extensions or bellows...Ray


PostPosted: Tue Mar 04, 2014 1:14 pm    Post subject: Reply with quote
Ray Parkhurst wrote:


For many objectives, the results with a decent tube lens can be as good or better than using the same objective with extensions.


Interesting, but still worse than second best. Most of the people on this board cry poverty a lot, but still ...

Ray Parkhurst wrote:
That said, it is not my preference either, but not due to quality concerns. Stacked lenses don't give any flexibility, since the magnifications are fixed ratios. You can use a zoom lens, but most of them don't give the best quality as a tube lens and are tough to keep at a particular zoom setting. For the application the OP is targeting, I still feel the best method is a good long working distance, finite microscope objective on extensions or bellows...Ray


Agree completely on the lack of flexibility. Even though I have a couple of decent microscope objectives -- none LWD -- I think that something like a reversed 25/1.9 CE II would be more cost-effective. But I'm quibbling about a very minor point.

OP, please don't take any of my comments in this discussion as opposition to trying things out.


PostPosted: Tue Mar 04, 2014 4:51 pm    Post subject: Reply with quote
Ray Parkhurst wrote:
danfromm wrote:
Ray Parkhurst wrote:
danfromm wrote:
Ray Parkhurst wrote:
CuriousOne wrote:
Any problems using CCTV lens for reverse mounting, besides vignetting?


Vignetting is more an issue with the tube lens than the objective.


Tube lens? What tube lens? I used the lenses I mentioned with a single stage of magnification, i.e., at the end of a string of LTM extension tubes filled with air. Special air, of course, that the uninformed will mistakenly take for ordinary air.


I think the OP is planning to stack the cine lens reversed on his 210mm or 400mm.


Interesting if true.

Why on earth would he do that? When we don't use real macro lenses and devices to get extension, we use reversed C-mount lenses and devices to get extension. I first learned about stacking lenses to get the magnification nearly 40 years ago, saw it as something people who had no resources at all did because it was better than nothing.

There's much to be said for inexpensive better than nothing, especially when resources are scarce. But nowadays all the old crap I bought for dimes costs pennies so I can't understand not going for at least second best.

Of course, I am spoiled. I mean, I've had heaps of LTM tubes and adapters for decades.


For many objectives, the results with a decent tube lens can be as good or better than using the same objective with extensions. That said, it is not my preference either, but not due to quality concerns. Stacked lenses don't give any flexibility, since the magnifications are fixed ratios. You can use a zoom lens, but most of them don't give the best quality as a tube lens and are tough to keep at a particular zoom setting. For the application the OP is targeting, I still feel the best method is a good long working distance, finite microscope objective on extensions or bellows...Ray


Actually you can zoom and change magnification also with stacked prime lenses by using their focusing helicoids.
In some setups I found that stacked lenses (in that particular case reversed Hexanon 40/1.8 and Minolta MD 100/4 Macro, resulting into about 2:1 to 5:1 magnification if I remember correctly) gave better results than from reversed front-lens itself btw.


PostPosted: Tue Mar 04, 2014 8:28 pm    Post subject: Reply with quote
I have large stock of microscope objectives, but none are LWD. Most are CZJ Apo planar type, starting 10x and ending with 100x ones.


PostPosted: Wed Mar 05, 2014 8:13 pm    Post subject: Reply with quote
Here is cat's brain slice from binocular microscope included samples:


catbrain by agudzera, on Flickr

The image really looks 3D in binocular scope. I've tried to show both foreground and background of image, so had to close aperture down to 16. This is why vignetting arised.

The lens are Vivitar 70-210/4.5+ Petri 35/2.8 (reverse mounted).


PostPosted: Thu Mar 06, 2014 12:14 am    Post subject: Reply with quote
CuriousOne wrote:
I have large stock of microscope objectives, but none are LWD. Most are CZJ Apo planar type, starting 10x and ending with 100x ones.


Hmm, something fishy here.
You started the thread with the question "whether it's possible ............ " and then you came up with the quoted sentence.
What's the catch?


PostPosted: Thu Mar 06, 2014 5:27 am    Post subject: Reply with quote
I initially mentioned that I have microscope objectives, but non LWD, as tread started to go again into that direction, I've again mentioned the situation.


PostPosted: Thu Mar 06, 2014 5:33 pm    Post subject: Reply with quote
Just won Samyang 18-28/4-4.5 lens on ebay, let's see how it will perform reverse mounted.


PostPosted: Tue Mar 11, 2014 2:43 am    Post subject: Reply with quote
CuriousOne wrote:
Just won Samyang 18-28/4-4.5 lens on ebay, let's see how it will perform reverse mounted.


I tried reversing a Nikon 18-55 kit lens once, and the result was interesting. While you get some benefit from the retrofocus designs on reverse lenses, you also pay the penalty of large lens diameter limiting your lighting angles. I went so far as to build some LEDs into a lens cap so I could get the lights in at a reasonable angle, and also tried axial technique, which worked very well but is a bit finicky. Only other issue with the zoom objective was the same problem that happens with a zoom tube lens...they tend to extend to their maximum focal lengths when mounted vertically. If you're going horizontal, no worries, but if vertical (as I do for coins) they need to be taped to keep them from extending, if you're using them at minimum FL...Ray


PostPosted: Tue Mar 11, 2014 5:21 am    Post subject: Reply with quote
Since I'm going to permanently fix the installation once results will be satisfactory, creep won't be an issue in my case. For the illumination purposes, I'm using matte lens cap, attached to reverse side of lens being photographed, and being illuminated by external flash, mounted on extension cord.


PostPosted: Mon Mar 17, 2014 4:09 am    Post subject: Reply with quote
I've recently aquired Vivitar 35-105/3.2-4 lens. For curiosity, I've tried to mount it in reverse to my 300mm Tokina and it worked way better than other lens:

1. With other lens I had "curvature" sharpness - i.e. I can have center spot sharp and edges unsharp, or edges sharp and center blurry. With this lens, this is gone.

2. With other lenses, if I close down aperture on reverse mounted lens, I've got vignetting, with this lens, I just get better sharpness/dof when closing aperture down!

Here's example:


Cat brain sample by agudzera, on Flickr


PostPosted: Mon Mar 17, 2014 4:02 pm    Post subject: Reply with quote
A question regarding the macro magnification.

The shot above is meant to roughly have 300/35=8.5x magnification.

I've put the same sample onto various microscopes, starting from cheap $50 ones, ending with high end $10k ones.

The same magnification (area of coverage) is achieved around 80x magnification set on microscope. Microscope give a bit better detail, but lower contrast. I've tried to increase magnification, and significally more details appear at 150x and above (400x was the maximum magnification available). So I can't wait when my samyang 18mm arrives, so I can try to get 300/18 combo, which should yeld 160x in microscope "X"-es.

So how these microscope "X"-s can be converted into my setup "X" -s ? according to my observations, I should roughly multiply my results by 10, to get the corresponding "X" reading of microscope?
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