Trying to start with macro... need some advice

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gk80
Posts: 2
Joined: Mon Apr 01, 2013 4:01 pm

Trying to start with macro... need some advice

Post by gk80 »

Hello, this is my first post here. I decided to write because I need some advice.

I'm trying to take some macro photos using available equipment but I'm not getting good results.

My camera is a Nikon D200 and I've the following objectives:

Nikon 18-200 f3.5-5.6
Nikon 50mm f1.4
Tokina 11-16 f2.8
Vivitar 28mm f2.8 (Pentax mount)
Takumar 135mm f2.5 (Pentax mount)
I've an adapter to mount Pentax lenses on my D200 camera (just adapter, with no glass).
I've lens reversal rings to mount any of the objectives inverted.
I also have a set of extension tubes (no AF).

When taking the shots I'm mounting the camera on top of a Manfrotto 055XPROB tripod and 808RC4 head.
The camera is left still on the tripod and I'm using a micrometer head to move the subject in small increments to be able to focus. It's very annoying and slow process but before buying some expensive dedicated macro rail I would like to know the possibilities of my current setup.
I'm shooting at 1/250 with an external old flash triggered with the on-cameara flash.
Camera is set to mirror lock up + delayed shutter release (0.4s).

I'm not yet considering stacking until I can get a good image quality... so... here is the results using different lenses combination.
I'm not showing single lense shots because I'm interested in going beyond that (more magnification).

Images are JPG as they came out of the camera, with no editing and no sharpening. Full sized images were resampled by photobucket so I also included small crops from the center of each photo. Subject is a small screw. Each thread is about 0.35mm (0.014").

First example, using extension tubes + 135mm takumar wide open at f2.5 + inverted 28mm stoped down to f5.6 (stopping down the 135mm instead of the 28 gives very poor results)...
Image

Crop from the center:
Image



Second example, using the "bazooka": extension tubes + 135mm takumar + inverted Nikon 18-200 set at 18mm and stoped down
Image

Crop from the center:
Image




What do you think? Why am I getting that poor quality and unsharp images?
What are your suggestions to improve this images?
I'm ok with this magnification, but I really want to improve image quality and sharpness.

Thank you very much for taking the time to read my post.

Chris S.
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Joined: Sun Apr 05, 2009 9:55 pm
Location: Ohio, USA

Post by Chris S. »

Welcome to the forum, gk80!

First of all, I think you're getting pretty good results for the equipment you're using. Combinations of camera lenses (long lens on camera, reversed short lens mounted in front) such as you're using, are hit or miss affairs, with a lot of misses.

You'll probably see a big improvement if you add a microscope objective to your arsenal. In your situation, you already have most of the things you need, so adding a microscope objective to your system need not be expensive.

You are shooting a camera with an APS-C sensor, which has a size that is ideal for many microscope objectives. Since you already have 135mm and 18-200mm lenses, you will want to look at "infinite" objectives, which can be mounted on the front of those lenses. Given the magnifications you've shown in your post, you'd probably be happy starting with a 10x microscope objective, which will deliver about 7x if mounted on the 135mm lens, and 10x if mounted on the 18-200mm lens at 200mm. (Note that with a microscope objective mounted on your zoom, the corners of the image will start to go dark at shorter zoom settings--just where this happens, I can't predict.)

For good recommendations on microscope objectives for your use, see Rik Littlefield's post here, fourth paragraph down. Be warned that many microscope objectives will not work for your application, so you probably don't want to purchase any that are not recommended at this forum, without first posting a question here.

You'll also want to look at FAQ: How can I hook a microscope objective to my camera?

On a side note, the subject you've shown here--shiny metal--has some surprisingly tricky behavior when photographed under light that is not highly diffused. With this subject, you may see a big improvement if you add considerably more diffusion to your lighting approach. (There is a long and very technical thread discussing this here, but all you need from it now can be summarized: "For shiny metal subjects, diffuse your light.")

Cheers,

--Chris

gk80
Posts: 2
Joined: Mon Apr 01, 2013 4:01 pm

Post by gk80 »

Thank you very much for your reply..

Is it possible to use a microscope objective with my Nikon 18-200 zoom?

If I understant what you wrote, using the 135mm + microscope objective will provide about 7x magnification with no vignetting. At the same time, using 18-200mm at 200mm end + microscope objective will produce about 10x magnification with no vignetting. But if I zoom the 18-200 to 135mm it might produce vignetting. Is this correct?

Is it any way to find out (before buying the microscope objective) if it will produce vignetting on the 18-200 at 200mm end?

About my subject, I choose it only for testing purposes. I'm not going to shoot screw threads. I thought it might be an easy subject to focus on and test for sharpness.
Right now I've my other computer processing my first stacked shots of an insect's head... I'll see if it ends up better than the screw threads.

Once again, thank you very much for your time and quick reply.

Chris S.
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Joined: Sun Apr 05, 2009 9:55 pm
Location: Ohio, USA

Post by Chris S. »

gk80 wrote:Is it possible to use a microscope objective with my Nikon 18-200 zoom?
Probably. To be absolutely sure, we’d need a report from someone who has already tried using the Nikon 18-200mm lens in this way [that is, as a “converging lens” (a term I prefer), or “tube lens” (a term that seems not quite accurate to me in this specific use, but is widely used)]. In a quick search just now, I didn’t come up with anyone definitively saying that the Nikon 18-200mm has been shown to work as a converging lens on an APS-C sensor. However, most zooms that have been tested as converging lenses do work at 200mm. Of course, if there were going to be an unhappy outlier, the 18-200mm, with its exceptionally wide zoom range, might be it.
If I understand what you wrote, using the 135mm + microscope objective will provide about 7x magnification with no vignetting. At the same time, using 18-200mm at 200mm end + microscope objective will produce about 10x magnification with no vignetting. But if I zoom the 18-200 to 135mm it might produce vignetting. Is this correct?
Yes, you understand correctly. I should add the caveat that, as with the 18-200mm zoom, nothing is every quite certain until someone tests it. I have no experience with the Takumar 135mm, but prime lenses around this focal length routinely work very well as converging lenses with certain microscope objectives on APS-C, so I’d be pretty surprised if yours does not.

Right—with zoom lenses used at much under 200mm, vignetting has been a problem with all zoom lenses we so far know about. This is due to the inner workings of the zoom lenses (specifically, the “location of the entrance pupil.”) I suspect that a 100mm-200mm zoom converging lens could be made, but so far as is known at this forum, no such animal has yet been found (other than lenses that only cover much smaller sensors, such as those used for machine vision).
Is it any way to find out (before buying the microscope objective) if it will produce vignetting on the 18-200 at 200mm end?
It would be easiest if someone who has a specimen of the 18-200mm zoom and an appropriate microscope objective would try them together and report back. Or perhaps this has already been done, and someone will point out a link. Barring that, you could perhaps cut a round hole the size of the candidate objective’s exit pupil in piece of dark paper, place it immediately in front of your lens—zoomed to 200mm and focused at infinity—and take a picture. But I’m not certain that this would be perfectly predictive, and don’t know the size of the exit pupils for the lenses recommended in the link above. (My objectives are different from these, so I can’t measure one for you.)

That said, you might just want to order the objective without worrying about the zoom lens question. A good microscope objective on your Takumar 135mm will likely do yeoman’s work, and if it also performs well on your 18-200mm, so much the better. In time, if you like, you might get an inexpensive, oldish 100 or 105mm prime lens, which would give you 5x magnification. And if the 18-200mm zoom does vignette, you pick up an inexpensive older 200mm prime to give you 10x magnification. Given your interest in macro work, a microscope objective seems like a very solid next step for you, regardless of whether or not it vignettes on your zoom lens.

Good luck!

--Chris

ChrisR
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Post by ChrisR »

I tried a Nikkor 28 - 300 on full frame, and it "worked" but was instantly unimpressive. The quality wasn't good, AND it vignetted when zoomed away from the long end, which, I believe, all the zooms anyone has reported, also do at some point. Yours at least starts at the right length!

Another vote for trying the 135.
With a 10x objective it'll give you
135/200 *10 = 6.75x magnification
and with a 4x objective it'll be
135/200 *4 = 2.7x magnification.
(because the magnification number on the objective assumes it'll be used with a 200mm "tube" lens.)

The 4x on 135 is less mag than you'll get with your 28mm on 135, but the qualilty should be better. 28mm camera lenses vary a lot, but they all have to be "retrofocus".

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