Match Head Focus Stack: Questions

[cshahar]

Hi. This is my first focus stuck (100% crop in image) and I am getting some out of focus banding. It is a stack of about 40 images. This banding concerns me, and I am wondering if I should get a better (more accurate) focusing rail. My equipment:

10X microscope occular
105mm lens
novoflex focusing rack

It is quite an old style focusing rack but very rugged. An image of the identical model can be found here:
http://www.flickr.com/photos/eoorider/6337560180/

Okay so the issue is that I tried my best to take as many images as I could between the smallest hash marks. I guess I didn't get enough. Is that correct? Should I find a rail with even more differentiated hash marks? The manual doesn't say exactly what the separation is between the smallest hash marks.

Also the exposure times were very large (5 sec), as I have not set up adequate lighting just yet. But that shouldn't be a problem.

Before I start taking pictures of insects I need to figure this out! Any help would be appreciated.

Thanks,

-Charles

[rjlittlefield]

Charles,

Congratulations on your first high magnification focus stack!

As you've noticed, microscope objectives have very shallow depth of field. I gather that you're pushing a 10X infinity objective down to about 5.25X by using it on a 105mm tube lens. In this configuration there is less than 0.02 mm DOF.

It is very difficult to make such fine steps with anything except a screw driven rail or a microscope focus block. The forum thread FAQ: What's the best way to focus when stacking? has a lot of options. Note especially the list of links at http://www.photomacrography.net/forum/v ... 5311#55311.

On a side note, it looks like your image is too orange and has lost some contrast. For the color, be sure your camera is set on the correct white balance. For the contrast, if you are using Zerene Stacker then try removing the checkmark at Options > Preferences > Alignment > Brightness. That option tells the software to match contrast and brightness for all images in the stack. If your stack starts with an image that is low contrast because it's mostly out of focus, then having Brightness checkmarked may inappropriately reduce the contrast of all other images to match the low-contrast OOF one.

I hope this helps!

--Rik

[cshahar]

Rik:

Thank you very much. that is helpful! I am looking through some of the suggestions now. My problem is that I am not very techno adept. So I can't really build my own system as some of the contributors have. Some have adapted their set-up from microscope parts. Do you have any specific suggestions regarding "screw driven rails or a microscope focus block"? I have looked around on eBay for microscope parts but it is difficult to know whether models for sale can be disassembled for my purposes. Are there any specific rails you would recommend that allow for such pinpoint accuracy that can be purchased from manufacturers or 2nd hand on eBay?

Thanks!

-Charles

[spongepuppy]

Hi Charles,

As someone having no skill with tools (and no tools), I am intimately familiar with your situation. The StackShot servo rail from Cognisys is a product I can wholeheartedly recommend. I'm very much at the beginner stage myself, and going with a motorized rail has taken a lot of the frustration out of the learning process, and has also dramatically simplified workflow.

At around US$500, it's quite inexpensive, given the additional capability it provides.

[cshahar]

Hi Matt. I have been thinking seriously about the stackshot. But herein is my dilemma: I am experiencing a lot of trepidation regarding my ability to collect dead insects (I won't kill them), be able to mount them, and deal with just generally handling them. I would have liked to see whether I can do all of that before spending about $600+ (after taxes and duties). But I guess I will make up my mind soon and maybe take the plunge with the stackshot! After all, a Micrometer Positioning Stage will likely cost me more than half that.

Do you have any shots on flickr I can see?

-Charles

[spongepuppy]

Hi Charles,

Only a very few so far. I have a long way to go (especially in the area of specimen handling).

http://www.flickr.com/photos/spongepupp ... 112433624/

I grapple with the ethical implications of killing organisms for photography too. I generally find that putting them in the fridge, before immersing them in ethanol, seems to cause the smallest amount of suffering.

Edit: I also have a personal policy of only collecting insects that cross my path, so to speak - rather than to specifically gather them in quantity.

[rjlittlefield]

You can't beat the StackShot for self-contained "plug and play" capability. Everything else I can think of at this moment is either fairly expensive, requires fiddling with tools, or both.

One very cheap option to consider: if you can borrow a microscope with a movable stage from a friend or a local school, then with a popsicle stick and some rubber bands or tape you can fashion an extension on the stage. Stick a subject on the extension, let your camera hover over it on a tripod, and by turning the fine focus knob you'll be able to make very small movements.

--Rik

[cshahar]

Hi Rik:

That's a great idea about the microscope! I shall start looking around for one!!

-Charles