just starting out in insect macro with ok results, but....

ctron · Post by **ctron** » Fri Jan 29, 2016 2:48 am

I currently use the Pentax K-x DSLR with an M42 200mm SMC Tak and a reversed Minolta MD 50mm 1:2 lens on front of the 200mm. This is what I had available and close at hand, but no cost because I already had them.

Initial indoor shooting quickly showed that I was going to have to use flash, so I brought out some old Wein peanut slaves (which I still had in storage from my hummingbird days), and some Vivitar 283 flashes, also each equipped with a Wein peanut (the flashes are set at 1/16 power). Results so far have been ok, but lack contrast.

About the only thing inside this time of year are the small, black house ants. With this set up, I am able to get about 3/4 of an ant across the field, but the result seems soft. I don't think it's a focus issue as I tried all sorts of manual micro adjusting of the subject/ lens-- more of a contrast issue I would guess. I have the lens aperture almost closed on the Minolta, which allows great DOF, but I just can't seem to get the sharpness I want and I would appreciate any suggestions. I can partially compensate for softness in Photoshop with unsharp masking, etc, but still not as sharp as I'd like.

I do have a Raynox DCR-250 on the way as I write, but I'm not sure how much difference this will make in front of the 200mm lens versus the Minolta, or even across the front of the Minolta because if I'm already having softness in the system, all the '250 will do is amplify it. The goal is for greater than lifesize. In a small, black ant for example, I'd like to fill at least half the Pentax FOV with the head only.

Appreciate any help and advice.

Thanks,
C

rjlittlefield · Post by **rjlittlefield** » Fri Jan 29, 2016 11:40 am

ctron, welcome aboard.

The combination of high magnification, closed aperture, great DOF, and soft result indicates a problem called "diffraction blur".

It is a fundamental limitation due to the wave nature of light, shared by all lenses no matter how expensive.

One result of diffraction is a strict tradeoff between DOF and sharpness.

To get a sharp picture of an ant head, there is no substitute for "focus stacking". This means shooting a large number of exposures, each with slightly different focus point, then running the whole collection of images through some computer software that rummages around, finds all the sharp bits, and puts those together to produce a single image that is in focus everywhere. This technique allows you to use a wide aperture lens that can be sharp but necessarily has shallow DOF in any single exposure.

Again, there is no way around the DOF/sharpness tradeoff just by throwing money at lenses. The way to get a sharp image of an ant head is to use a microscope objective -- which does not need to be expensive -- combined with focus stacking. See our FAQ: How can I hook a microscope objective to my camera? for more information.

--Rik

ctron · Post by **ctron** » Fri Jan 29, 2016 2:03 pm

Hi Rik,

First off, thanks for your fast response. While waiting for a response, I decided to investigate a bit further and I sort of realized that the microscope objective may be key. I actually have two telephotos I'd like to use, a Zeiss jenna 135mm and a SMC Tak 200 mm. As for softness, I'm not sure if it's the lens(es) or the diffraction blur. The Minolta 50mm is currently reversed on top of the 200mm Tak. At first, I stopped down the Minolta almost completely, but maybe I should leave that alone and stop down the Tak instead (?).

I have some other questions at some point, but for now I'll just stick to the task at hand. When the Raynox DCR-250 arrives, I had planned to place it in front of the Tak/ Minolta combination first. Would this simply multiply the 4x I get with the Tak/ Minolta now to 10X (I am guessing that the Raynox is now multiplying the combination)? If so, I don't even think I'm going to try this combination, but will switch out the Tak for the Zeiss. The Zeiss is very sharp and I have used it for astronomy. I've used the Tak too, but I *think* it is softer.

At some point, I'll have more questions on the microscope objective/ telephoto set up, but for now I'm just going to try and see if I can improve on this existing system for better sharpness.

thanks,
C

Charles Krebs · Post by **Charles Krebs** » Fri Jan 29, 2016 4:02 pm

I have the lens aperture almost closed on the Minolta,

This is your current primary problem... diffraction. It usually is best to use the aperture on the front lens, but you can't stop down that much. Do some simple testing starting with the aperture starting "wide-open" and then gradually closing down by a stop (or half stop if the lens has those indentations). Find the aperture that provides the best "sharpness". Don't look at the DOF. You are (at lowest) working at 4X (200/50). As Rik mentions, at these magnifications the DOF (at an acceptably sharp aperture) will almost surely be "too shallow" for your needs and you will need to do some image stacking.

rjlittlefield · Post by **rjlittlefield** » Fri Jan 29, 2016 4:08 pm

ctron wrote:As for softness, I'm not sure if it's the lens(es) or the diffraction blur. The Minolta 50mm is currently reversed on top of the 200mm Tak. At first, I stopped down the Minolta almost completely,

Diffraction blur is surely a huge part of the problem. Reversing a 50mm in front of a 200mm gives at least 4X magnification. Your 50mm probably stops down to f/16, but combined with the 4X magnification that turns into effective f/64 on the camera side. With an APS-C sensor, that is far into diffraction territory.

... but maybe I should leave that alone and stop down the Tak instead (?).

At image center it doesn't make any difference which one you stop down. They have exactly the same effect on the optical image. Away from center, it's probably better to stop down the front lens (for you, the Minolta), but that's a matter of other aberrations. See FAQ: Stopping down a lens combo for more discussion.

When the Raynox DCR-250 arrives, I had planned to place it in front of the Tak/ Minolta combination first. Would this simply multiply the 4x I get with the Tak/ Minolta now to 10X (I am guessing that the Raynox is now multiplying the combination)?

No, lenses used like that don't come even close to multiplying. The Raynox DCR-250 is just another 125mm lens, corrected to be used in a certain way. So what you'd be doing is stacking a 125 in front of a 50 in front of a 200. In unrealistic theory, assuming "thin" lenses, that might bump you up to 5.6X. Realistically, because of the thickness of the lenses it will probably be a lot less than that. In the worst case you may not be able to focus at all.

will switch out the Tak for the Zeiss. The Zeiss is very sharp and I have used it for astronomy. I've used the Tak too, but I *think* it is softer.

Swapping in the 135mm Zeiss in place of the Tak 200mm will reduce your magnification by roughly a factor of 135/200. This will result in an image that is sharper on sensor. However, for resolution on subject, mostly what matters is the short lens in front. The long lens in rear effectively gets stopped down by the short lens in front. If you had that front lens stopped down to its sharpest aperture, say f/2.8 on an f/2 lens, then that 200 mm in rear would effectively be stopped to f/11 (=4*2.8 ).

for now I'm just going to try and see if I can improve on this existing system for better sharpness.

Given the equipment that you're using, the most valuable next step would be to run a test sequence, varying aperture of the front lens from wide open to full closed. Assuming that you use a flash to avoid issues with vibration, you'll probably find that the sharpest aperture is a stop or two down from wide open on the front lens.

Edit: I see that Charles Krebs posted while I was typing. No problem -- it's the same content. I just use more words.

--Rik

ctron · Post by **ctron** » Fri Jan 29, 2016 6:16 pm

Thanks, guys. Taking a closer look at the Minolta lens, f/2-22, so I had it at either f/16 or f/22 which, as mentioned, is most likely the cause of the softness. Ok, will retry while adjusting the stop, probably focusing on an inanimate object tomorrow. Quick question on focus stacking: is it possible to do it on a live insect, like an ant? I would guess much better to have something dead or at least somewhat paralyzed from the freezer while taking images.

ChrisR · Post by **ChrisR** » Fri Jan 29, 2016 6:44 pm

Quick question on focus stacking: is it possible to do it on a live insect,

QUICK answer, is no.

Moth wings are good. Glass slide, double sided sticky tape, works, and is fairly flat.
So is fine "wet and dry" abrasive paper, but it doesn't have the appearance of a real object.
Keep the light more diffuse than you'd think necessary, eg by surrounding the subject in a tube of white paper, or strange things happen.

NikonUser · Post by **NikonUser** » Sat Jan 30, 2016 8:35 am

ctron wrote:Quick question on focus stacking: is it possible to do it on a live insect, like an ant?

Yes! Perhaps the question would be better rephrased `.....on a moving insect.'

Then No!

I frequently focus stack live bugs. The `trick`is to contain then in an arena.
Give them some water (damp paper) and maybe a tiny bit of sugar.
They will be very active for the 1st several hours but will eventually settle down (insects have to sleep).

Any slight movement during exposures will be readily taken care of with Zerene Stacker.

ctron · Post by **ctron** » Sat Jan 30, 2016 9:12 am

Thanks for your kind and informative responses so far, all. Well, today's update= not good! I manipulated Minolta lens aperture from open all the way to f/22. When nearly open, I was having a lot of trouble with light control and there's just a VERY small area of the ant that may be in focus. When looked at full size, even wide open, I think the image still seems soft but hard to tell.

I then decided to swap out telephotos from the 200mm Mak to the Zeiss Sonnar 135mm with the Pentax 18-55 mm "kit" lens reversed in front. The best shots seem to be when the aperture is about f/8-10, but full size is still showing softness despite using a tripod. At 18mm, the ant head is definitely larger and I can even focus to see hairs, but still soft.

I'm beginning to wonder if I should approach this another way, perhaps with an enlarger lens reversed at the ends of bellows (or even just the Minolta reversed at end of bellows). I'm pretty much set on the microscope objective for the head only when the times comes, but these in between sizes from full ant in frame to partial ant with the lenses and method I'm using are, so far, not panning out.

ctron · Post by **ctron** » Sat Jan 30, 2016 1:41 pm

Ok, another update. I completely swapped out the telephoto lenses and, using some spare macro tubes, I mounted the 18-55mm kit lens in reverse with a couple of inches of macro tubing for more magnification. As a result, the ant I'm seeing is actually a little larger than the telephoto/ lens combo (at the 18mm setting), but I'm still not getting things right. I have the aperture set about halfway and still don't have much DOF.

I found a fresh ant and placed it on a "bridge" inside of a Dixie cup. Unfortunately, it kept falling off of the bridge and climbing out the side. I tried using Vics vapor rub as a barrier, but it climbed right over it.

I think for these larger ant images, I'm definitely going to have to look into image stacking as well as cooling the ant so it doesn't move for a while. However, the biggest challenge is going to be implementing a macro focus rail. I do have some in the x-y plane that I used for another purpose several years back. They were modified with motors and I hope I can adjust focus in small enough steps.

To be honest, I'm getting frustrated here. I would have never thought it would be this difficult to get a reasonable ant image that was in focus and had the right lighting, so any more suggestions would be welcome. I'm an amateur astronomer and know well how important focus is to getting that desired starry result, but I'm finding this process even more difficult!

ChrisR · Post by **ChrisR** » Sat Jan 30, 2016 3:05 pm

There's current thread with fairly similar considerations, here: http://photomacrography.net/forum/viewtopic.php?t=29840

Have a look at Paul Bertner's close-ups of ants, eg here, second post.
http://photomacrography.net/forum/viewt ... 566#175566

He generally uses something around f/11, no stacking.
(See his blog for more details.)

No you won't get much in focus. Much less than 1 millimetre. The bigger the image, the more obvious that becomes.

ALMOST every time I've stacked anything which is still alive, there's been an antenna or something moving. One antenna you can "put back". Six legs, no!

ctron · Post by **ctron** » Sun Jan 31, 2016 3:55 am

My results, so far, are here based on yesterday's experiments and a day before:

http://www.photomacrography.net/forum/v ... 275#184275

I'm finding that the kit lens in reverse is producing a sharper result, even though the lighting is poorer this time. I think I'll put away the telephotos and stick with just the reversed kit lens for now.

Both images had to have some Photoshop treatment to offset softness, although far less in the larger ant image (in fact, I could probably get away with no treatment if I start stacking).

First ever macro images.

ctron · Post by **ctron** » Mon Feb 01, 2016 6:20 am

Further experiments, this time with the demo version of Zerene stacker. I can really see the potential here, but trying it out has also revealed the weaknesses of my set up

.

Looks like I'm going to have to ditch the multicolored toothpicks in favor of a much more uniform background.... what would be recommended for ants? Something reusable that the ants can walk on and sugar feed while I snap images.

I seem to be getting a glare right about in the center of the ant images I'm taking. Not severe, but still have to Photoshop it out. At first I used no diffusers on the Vivitar 283's, but then I placed a latex glove over the end. I don't think this helped too much. Could the glare still be caused by improper flash placement or lack of diffusion or ?

Finally, the CMOS/CCD of my DSLR has so many dust spots that they are a problem. When I snapped single images, I could get by by using Photoshop's healing tool, but Zerene greatly increases the number of unstacked spots. This may be OT, but can anyone recommend a home method for cleaning camera CCD?

Sorry, forgot a bit of good news.... at least it appears that my motorized macro rail appears to be working! The motor has fast/ slow movement, so I can really go slow with the focus. Now if I can find the remote for my camera so I don't have to touch it each time I want to take an image, I'll be in business in that aspect (unfortunately the KX only has wireless IR remote for the shutter).

ChrisR · Post by **ChrisR** » Mon Feb 01, 2016 7:26 am

How about a leaf background?

Your reversed kit lens will need a lenshood because it's not coated to resist side light at the normally unexposed end.

Also you will get problems if there's anything reflective between the lens and the camera.
Remove any filter, but also look out for shiny adapters, tubes etc. Usually black tape or black paper is adequate to "kill" them.

ctron · Post by **ctron** » Mon Feb 01, 2016 11:01 am

Chris, here is my recent attempt:

http://www.photomacrography.net/forum/v ... 409#184409

You can see the glare/flare coming from the ant's center, numerous CCD dirt that I didn't try to remove, and the ant is still too dark. Will try to fashion some sort of lens hood later today.