10x magnification with good image quality / croppability.

acroporas · Post by **acroporas** » Tue Apr 28, 2009 8:22 am

Currently I use a Canon 5D with Sigma 150mm Macro + Kenko 1.4x Teleconverter + Canon 500D diopter.

This combination at full close focus results in 1.9x magnification. Which is very fun, but I am looking to increase the magnification I can photograph. Ideally I would like to get to 10x. I will not be happy if the image quality is any worse than what I get now with my current setup.

Budget is $1500. I am pretty sure that my current tripod and lighting will be suitable for use at 10x, so if they will be needed, things like a focus rail or lighting will need to be included in this budget. If the budget is a problem, I would rather sacrifice magnification than image quality.

As far as technique required and difficulty of use, that is not important to me, so long as I can get all of the equipment needed and stay within my budget. Portability is also not an issue, I have no desire/need to photograph at this magnification in the field.

I would be happiest if the solution was a compound microscope, because it has the potential to achieve much greater magnifications, so if a microscope can fit my budget and meet my image quality expectations, that is my preference, but I am open to traditional camera equipment as well if that is what will get me the best image quality at 10x considering my budget.

______________

So here are my image quality expectations.

Here is an example of what I can achieve now at 1.9x. (this was hand held, with a single flash to the side, I'm sure I could get better contrast with more controlled lighting) So I want to be able to start at 10x and still have it hold up to this heavy of cropping.

Uncropped image:

With 100% crop: (fyi, units on scale are mm)

rjlittlefield · Post by **rjlittlefield** » Tue Apr 28, 2009 10:02 am

acroporas, welcome aboard with your first post!

To get that same level of cropped resolution at 10X on sensor, you will have to use a microscope objective. Conventional macro lenses will have too much diffraction blurring due to their smaller apertures.

There are two common ways to use the microscope objective. One of them is to couple a camera to a microscope. The other is to mount the objective on the end of a bellows or other extension, using it as if it were a macro lens with a wide fixed aperture.

Both approaches have advantages and disadvantages.

Coupling a camera to a microscope gives a smooth path to higher magnifications. It also plays nicely with condenser illumination and provides a built-in fine focus mechanism. However the "closed" layout of the microscope frame makes it more difficult to position and illuminate 3D opaque subjects.

Mounting the objective on bellows is exactly the opposite -- easier to position and illuminate 3D opaque subjects, but more difficult to fine focus, to control trans-illumination, and to grow into larger magnifications.

But this is not really an either-or situation. You can, for example, put most of your resources into a microscope, and pick up a bellows and mounting adapter on the side. The microscope is then available for use when it works well, and if you need the freedom of the open setup, you can use the microscope stage to provide fine focusing.

Focus stacking will be required for most subjects at 10X, so don't forget to account for computing resources. You may also want to consider flash illumination, particularly for the objective-on-bellows approach where vibration is more of an issue.

A lot of what's feasible for $1500 depends on your level of scrounging and do-it-yourself skills. Buying a turnkey system for that price will be challenging; putting it together with stuff from eBay should be no problem for the budget, but significantly more troublesome.

There has been a lot written in the forum about this general topic. I suggest to spend some time searching and reading, then ask again. Once we have a better idea of what you are thinking about, we can provide more specific pointers.

--Rik

acroporas · Post by **acroporas** » Tue Apr 28, 2009 1:09 pm

Thanks for the advise. Your post is very encouraging. I should be able to get the image quality I want with a microscope and stay within my budget. But before you send me off to do some more research on my own, can you give me a bit more?

From what I have gathered the microscope object magnification is not the same as the definition of magnification used in photography. Can you point me to a explanation of the two different "magnifications" and how to convert from one to the other? Or if it is easier, what magnification objective would I use to get an equivalent to a photography scale 10x magnification?

How can I figure out which microscope objectives are capable of meeting my image quality expectations? I understand the concepts that effect the image quality of of microscope objectives, but I do know how that translates into the right objective for me.

rjlittlefield · Post by **rjlittlefield** » Tue Apr 28, 2009 3:47 pm

William,

There are numerous definitions of magnification used in photography and microscopy.

The one I think you are using when you say "1.9x" is that the image on sensor is 1.9 times as large as the real subject.

What this means as a matter of practice is that your current setup will photograph a subject field down to as small as 12.6 mm x 18.9 mm, that is, 24 mm x 36 mm sensor size, divided by 1.9 magnification.

Assuming that you're using the same criterion for "10x", then what you're looking for is to photograph a subject size down to 2.4 mm x 3.6 mm.

In microscopy, a 10X objective will deliver an image to the eyepiece that is 10 times larger than the real subject. However, the field of the eyepiece is typically only about 25 mm wide, and it takes a good objective to fill that circle with high quality image. The corresponding field of a 10X objective is thus only about 2.5 mm diameter, somewhat less at high quality.

The diagonal of a 2.4mm x 3.6mm rectangle is about 4.33 mm. So, to fit that size subject into the field of a microscope objective, you would really need an objective rated around 25/4.33 = 5.8X. In standard powers, 5X would work well and would give you some leeway to crop off degraded image at the outside of the field.

Once you have that 5X objective, the next challenge becomes how to transfer the image onto the sensor of your camera. On a microscope, the best approach is to use what's called a "projection eyepiece" that is specifically made to do this job. With the 5D's 24 mm x 36 mm sensor, any projection eyepiece made for 35 mm film should be a good match. With objective on bellows, you can simply increase the extension if needed to fill the frame. This will work OK with low power objectives (5X and 10X). With higher power objectives, adding extension can degrade the image quality somewhat.

Thinking through these numbers again, I notice that I'm now talking about a 5X objective, not a 10X objective. The optical quality of a 5X objective can be matched by very good macro lenses. So if you were absolutely sure that your target magnification range would extend only down to 10X on sensor, then a very good short macro lens might be a reasonable option. But given your stated interest in growing to higher magnifications, it still seems to me that microscope would be the better way to go.

There are other members who know more about coupling cameras to microscopes than I do. Hopefully one of them will drop by to correct any errors or omissions in what I have written.

In the meantime, take a look at http://www.photomacrography.net/forum/v ... c.php?t=12 and chain through the links that it gives, to see one very good scheme for coupling a DSLR to a microscope.

--Rik

acroporas · Post by **acroporas** » Tue Apr 28, 2009 5:23 pm

Thanks, let me see if I follow.

A 10X objective projects a 25 mm diameter image of a 2.5 mm subject.

But if I want to make the image fill the sensor, I must enlarge the image either by optics or by increasing the lens to sensor distance so that the image will to fill my 43mm sensor.

So after enlarging the image, I have a 2.5mm subject, projected as 43mm image. 43/2.5 = 17.3.

So a 10x objective will result in 17.3x magnification.

So I can say that the magnification = 43 * objective magnification / 25
Or desired objective magnification = magnification *25/43

So to get 10x I would need a 5.8x objective.

Perfect.

So now to part two: how do I figure out which objectives, and thus which microscopes are capable of giving me the resolution I am after.

g4lab · Post by **g4lab** » Tue Apr 28, 2009 8:31 pm

William
In order to do that which you are trying to do, there are some principles to keep in mind.

The first is surely "There are many ways to skin a cat" Easily three or four ways in this case.

The second would then need to be, "The devil is in the details"

As Rik noted if you are willing to shop on ebay and fuss a bit the budget you mentioned is plenty. If you want to buy all new stuff and have it be plug and play then it probably is not enough.

You really should study the archives of this forum because just about everything you need to know has been plowed over several times.

A third thing you should keep in mind is that whenever you adapt a camera and a microscope or microscope optic to one another there are two aspects, mechanical and optical. The microscope, or copy stand or bellows arrangement has to stably hold the scope and camera together and also the optical arrangement has to be able to bring the image to focus where it needs to be. Therefore see rules one and two.

I would say that most members of this forum fall into the "buy it on ebay and adapt it yourself" category.

A shortened answer to which objective to get would be to get one of the Nikon Chromatic Aberration free series CFN objectives of 10x or less initial magnification. These have the advantage that they don't mind being used without an ocular lens (as in the case of using them on a bellows).
This recommendation refers to the 160 tube length lenses and maybe to the 210 series but NOT to the infinity corrected series.

In that characteristic they are rather similar to so called true macro lenses like Zeiss Luminars and similar competitive lenses. But testing by some of our members have shown them to be superior in performance. There are also similar objectives in the range 1x to 10x. (True macro lenses run from about 12.5mm to 200mm focal lengths)

There are many aspects to microscope purchase, more than can be given in a single post.

You should mention to us 1) whether you are ready willing and able to make modifications to things and fit them together even if they were not made for a particular purpose. 2) what specimens are you interested in photographing.

I would advise against just running out and buying stuff because it is very easy to make expensive mistakes. There are probably many here on the forum that would offer guidance. Once you have a better idea of what you want and need very good buys can be made on ebay, and a few other spots , very regularly.

Gene

Charles Krebs · Post by **Charles Krebs** » Tue Apr 28, 2009 11:25 pm

William,

You might get a few pointers here:
http://www.krebsmicro.com/obj_bellows/index.html

acroporas · Post by **acroporas** » Tue Jul 21, 2009 9:28 pm

Thanks for the advise. Particularly with the recomendation of the Nikon CFN objectives. That is exactly the kind of advise I was looking for.

I ended up deciding that even though 10x was/is my target magnification, it is probably unwise(from a learning curve POV) to jump from 1.9x to 10x.

So I ordered the MP-E 65 and a RSS focus rail. Once I have conquered 5x I can move on to my quest for 10x.