Canon 200mm Prime as a Rail.

[jsp]

I did some measurements, and I thought I would put them up here in case they are of interest to anyone else coming along behind me.

Here's what I found.

I set up the camera with the Canon 200mm prime lens, and a mity objective, looking at a stage micrometer. I set the stage micrometer at 45 degrees to the lens so that I could sort of measure depth of field of the lens combination.

I took a photo of the stage micrometer with the focus ring of the 200mm prime lens turned as far as it would go in one direction. I then turned the ring as far as it would go in the other direction. As I was turning, I counted how many lines on the stage micrometer came into focus. The stage micrometer is marked in hundredths of a centimeter, so this test gave me an indication of how much depth of focus I could get from a full stack with the given lens combination measured in hundredths of a centimeter.

I have attached two images. One is a single slice image of the stage micrometer, and the other is a full stack.

Here are the measurements that I got:

Canon 200mm prime + 50x Mity: Only one black line on the micrometer can be brought into focus. Working distance (WD) is 12.5mm.

Canon 200mm prime + 20x Mity: Two black lines could be brought into focus, so stack DOF was 1/100th cm. WD 15mm.

Canon 200mm prime + 10x Mity: Five black lines could be brought into focus, so stack DOF was 4/100th cm. WD 32mm.

Canon 200mm prime + 5x Mity: Stack DOF was 17/100th cm. WD 34mm. The width of this image, measured with the stage micrometer was 70/100ths of a centimeter.

I then tried adding the Canon Extender EF 2x III to the 200mm prime and 5x mity combination: stack DOF was still 17/100th cm. WD 32mm. The image was 35/100th cm wide.

I think it's interesting that I can double the magnification without losing any depth of field using the Canon Extender EF 2x III.

I also tried my Zuiko manual focus lens but it is no good for this because the front of the lens moves back and forth when I focus.

[jsp]

I just pushed the boat right out and made up this combination:

Canon 5D MkII + Canon extension tube EF12 + Canon extension tube EF25 + Canon Extender EF 2x II + Canon 200mm f/2.8 prime lens + 5x Mitutoyo lens.

The DOF for a full stack from that combination is still 17 hundreths of a centimetre. The width of the image is 26 hundredths of a cm, and the working distance is about 34mm.

[Pau]

This seems a crazy setup! (although experimenting can be fun )

With the extension tubes you put the lens very far away o the ideal infinite focus, the tele extender alone with the lens will work but you will get 400mm, way too long

Don't expect good quality, do you?

[Lou Jost]

What's the point of using the extension tubes? I don't think this will help anything. The teleconverter by itself can be helpful with lower power objectives.

[jsp]

It just gave me more magnification and I didn't see any degradation in quality. I will try experimenting with more detailed subjects.

[jsp]

These are my tests for today.

Not sure what I think of them yet.

I used my ring as a subject because it is translucent like the ferns so presents similar challenges in lighting.

I took these by turning the focus ring by hand and pressing the shutter button on the camera by hand. There were two flashes.

[jsp]

This is the x5 cropped better so it give an impression of what I'd get by using this lens and then cropping, rather than using the x10 lens.

[jsp]

This is the same photo taken with the Canon 100mm Macro lens and the 10x Mity. The focus ring needs to be turned in much smaller increments to avoid stripes.
This was lit with a torch pointing a the ring rather than flashes with a difuser.

[jsp]

This is my bit of photography for today.

I tried the 100mm prime with the 20x Mity. The photo did not turn out well and I'm not sure why, because Rik got the 50x to work, so it should be possible with the 20x. I did two stacks and both were really quite bad.

The image was taken again by turning the ring by hand and pressing the shutter button on the camera. The image was lit by flashed, with a polystyrene cup as a diffuser.

One thing that I notice is that the 100mm prime is less stable when I turn the focus ring by hand, because the 100mm is quite a light lens compared to the 200mm which is very very heavy and stable. It's possible that the the 100mm is shifting a tiny bit as I turn the ring.

The stack DOF for this lens combination, measured with my stage micrometer is 10/100ths cm. The working distance is 20mm and the image is 25/100ths cm wide. In an individual slice the DOF is only 1/100th cm.

From my experiments so far, I am getting the best results with the 200mm prime + 5x Mity + extensions.

I'm pleased with my setup of turning the focus ring by hand and using the camera shutter button to trigger the shutter because it means that I could do photography outside, using outside light. I think that might be better for my fern subjects which are very sensitive to camera flashes. I will need to wait until the ferns grow to see if that will actually work.

[jsp]

This is a leaf, photographed outside with only daylight and no diffuser. The base was a wooden board. The camera was just laid on the board, and the leaf was bluetacked to the top of my conference mic, which happens to be about the right height. I turned the focus knob by hand and triggered the flash by hand using the camera button.

As luck would have it, the 200mm prime lens is just the right width at the front that if I lay it on the board, the lens is parallel to the floor, so no propping is required.

The day was cloudy so no diffusing was required, but the light was not bright enough for good settings, and I had to use 1000 ISO.

The lens combination Canon Extender EF 2x II then Canon 200mm prime and the 5x Mity.

The image is not terrible but there is clearly some movement in the camera when I am turning the knob and firing the shutter as I can see the movement on the live view screen. Thsi problem is then visibible in the stack where the image is just not great.

I'm not sure why I am getting that movement when I work outside, as the set up is identical to the setup I used indoors where that movement was not a problem. Will have to think about that.

This setup is great for being quick (total 8 minutes from start to finish) and for being lit only with daylight.

[jsp]

This is the same subject photographed indoors with flashes and a diffuser. With the extra light I was able to change the settings to faster shutter speed (1/160th) and lower ISO (100).

This photo is better, so possibly outside would work fine if I just wait until later in the year when the sunshine is brighter. Not sure if it is sharp enough though.

[Lou Jost]

I don't remember if this has been discussed before in your threads, but you may not need to turn the focus by hand. The Magic Lantern software for Canon cameras will do that for you.

[dolmadis]

I don't remember if this has been discussed before in your threads, but you may not need to turn the focus by hand. The Magic Lantern software for Canon cameras will do that for you.

I think that Jennifer has mentioned Helicon Remote before. Thoughts?

John

[jsp]

Hi,

Thanks for commenting. I was just thinking the very same myself. :-)

I went back to helicon remote and fought harder with the user interface. This photo was taken with the camera under the control of Helicon remote and without me touching it at all during the shoot.

The lens was Canon 200mm + 5x Mity. The photo was taken indoors with two flashes and a polystyrene cup as a diffuser. (The same one I've been using since I started in 2018 - it's looking a bit bashed up now.)

I focused the lens to the opposite of infinity (whatever that's called) and set it to take 1000 photos at intervals of "5" I'm not sure what the units are.

[jsp]

This morning I took a couple of photos of a lichen. The lenses used are noted under the images.

I took the stacks indoors, with two flashes and the polystyrene cup as a diffuser. The camera was driven by Helicon Remote.

I ran the stack for 100 shots working towards infinity, with 4 steps between shots.

I figured out that the steps are just the smallest steps that the lens can take, which is presumably to do with the programming in the camera that contols the stepper motor in the lens.

It seems to me that the x10 lens stack is sharper, but clearly with less depth of field in the stack, while the x5x2 achieves greater depth of field with the downside that we lose sharpness.

I won't know which is the better combination for my subjects until they have grown big enough to try.