First attempts show serious vignetting

[NewForestTel]

I am a newbie to photomicrography although I have been learning on the site regularly for about 2 months.
I have just organised a photomicrography setup similar to setups that I have seen on this site.
I am using a Canon Eos 1DS Mk3 (Full frame) with a Canon EF 100mm f2.8 USM Macro lens (not the latest version) and a Nikon Plan 10x/0.25, Infinity objective.
To test the system with an "insect size" test piece I am trying to photgraph a small Rawlplug - end on.
Whatever I do I get a substantial vignetting effect. I have tried using a Canon EF12 extension tube but to no effect. I do not have any more extension tubes.
I am aware that a Full frame camera can cause this but I thought that it could be overcome.
What is the solution? Do I need bellows to extend the distance from sensor plane to objective to about 200mm or should I buy a straightforward 200mm lens.
Any advice and suggestions would be gratefully received.
Many thanks

[rjlittlefield]

NewForestTel, welcome aboard!

Short answer, you need to get a 200 mm lens. If this is just for macro use, then I recommend going with a repurposed Raynox DCR-150 "closeup lens" as discussed HERE, using a simple setup such as extension tubes as illustrated HERE, the bottom option using larger diameter tubes near the camera. Be sure to flock the tubes. This combination is known to work well and is relatively inexpensive (a couple hundred dollars for the lens, tubes, and adapter rings). Some 200 mm telephoto lenses will also work well, but it depends on the model so if you want to go that route some further research will be required.

The longer explanation is that you currently have two problems. The first problem is that because of the 100 mm rear lens, you're actually running that 10X objective at around 5X. At 5X, your 43 mm diagonal sensor would image an area on the subject with diagonal 8.6 mm, and that is significantly wider than the 10X objective will cover with good quality. So, nothing that you do with a 100 mm rear lens will be very successful unless you commit to cropping away the edges and using just the center of the frame. The second problem is vignetting. Those dark corners occur because the entrance pupil of that 100 mm lens is located too far back to pass light rays at the edges of the field. Using a different type of 100 mm lens could work around that problem, but still the corners would be low quality because of the first problem. The combination of that objective and a 100 mm rear lens can work splendidly on an APS-C sensor, but not on full frame.

--Rik

[NewForestTel]

Many thanks for your prompt reply to what must seem a naive question from a newbie.
I will follow up your suggestions and report back. My first port of call is to try my son's APS C Camera and see what results I get there.

Another follow on question - if you don't mind?
I have a Lumix GX7 camera (Micro 4/3) together with a Lumix G Vario 35-100mm F2.8 lens (58mm lens cap) and a Lumix G Vario 100-300mm F4.0-5.6 (67mm lens cap). Could this camera and one of the lenses be used for photomicrography and if so what would the camera setup need to be?
Once again many thanks for your patience and understanding

[ChrisR]

Hi Terry

The GX7 will almost certainly "work" with one or the other or both lenses.
As Rik explained, the Focal Length part, is in range. The position of the Entrance Pupil WILL probably be an issue, though.
Your cereal box and some electrical insulating tape should tell you enough about whether it's going to be good or not. (That tape comes off metalwork ok, in my experience). You can probably tape the adapter you have, to your Lumix lens(es).
Is the adapter conical or flat? Flat would be better to minimise vignetting (applies to the Canon too).

You should be able to get both cameras working pretty well. One difference is that ( I think) the GX7 won't have a vibration-free shutter mode ("EFSC") and I don't know about its flash connections - though you can always use a slave.

[NewForestTel]

Thanks Chris for your prompt and valued reply. Despite having enjoyed general photography for many years I can see that I am on a very steep learning curve with photomacrography and will have to research some of the optical terms used.
I do appreciate the patience given to my enquiry and will now go away and experiment as suggested.
Regards and best wishes

[NewForestTel]

Thanks for all the help I have received to date. I am now gathering all the bits and pieces recommended HERE and am just waiting for one item.

The general consensus is that I should flock the extension tubes and I have found Black flocking paper at Edmund Optics. However there are several grades and a choice of adhesive and non adhesive Is one version better than another and should I flock each of the extension tubes individually and screw together or should I chose the optimal length of extension tube and flock the whole as one piece?

Many thanks for the anticipated help

Terry

PS In the preview it does not look as though I have treated the url included in the correct way

AdminCS edited to format URL

[NewForestTel]

Another question if I may.
The setup I have almost assembled is the one using the Raynox 150 as outlined in Riks article
I am using a full frame camera (Canon EOS 1D Mk4 and a Nikon Plan 10x/0.25 infinite objective. What is the optimum lethgth of extension tubes I should make from sensor to Raynox or from sensor to objective. I have seen figures ranging from 160mm to 208mm.?
Thanks to all
Terry

[Pau]

I am using a full frame camera (Canon EOS 1D Mk4 and a Nikon Plan 10x/0.25 infinite objective. What is the optimum lethgth of extension tubes I should make from sensor to Raynox or from sensor to objective. I have seen figures ranging from 160mm to 208mm.?

The optimum is when the tube lens (your Raynox) without the microscope objective is actually focussed to infinite. Easy to test focusing a far subject like the house at the opposite side of your road

[Chris S.]

. . .I have found Black flocking paper at Edmund Optics. However there are several grades and a choice of adhesive and non adhesive Is one version better than another and should I flock each of the extension tubes individually and screw together or should I chose the optimal length of extension tube and flock the whole as one piece?

Terry,

I don't recall seeing any user reports on the Edmund Optics flocking products. But I've bought quite a few things from Edmund, and each has been very good at what it does--so their flocking materials are likely to work pretty well. (If you use them, you can inform the rest of us. )

For the light-trapping products I see at Edmund Optics, only the Light Absorbing Black-Out Material seems reasonably priced for a photomacrographer. The Acktar Light Absorbent Foil products are frightfully expensive, and might not actually work very well for our use.

As to adhesive vs. non-adhesive, I'd suggest getting the adhesive version. If you don't want adhesion for a particular application, simply leave the protective backing on the flocking material.

BTW, what I and quite a few others use for flocking is Protostar Hi-tack flocked light trap material. This has a fuzzy, felt-like surface, and works very well.

Whatever you go with, I suggest you order extra, because glare is an enemy of the macro photographer, and this will probably not be the last time you want to flock something.

Whether to flock components individually or with one long tube is a matter of convenience and practicality--do whichever works best for you. The key is that when an assembly is properly flocked, you can look through it with where the camera goes, not be able to induce shine or glare off of any internal surface. Do this test while moving the assembly with a bright light source just outside of view. Also try it with a directional light source aimed into the assembly, but not directly into your eye. Try hard to make glare form during this sort of test--if you can't, you've done a good job flocking. Anything less is asking for trouble.

(For completeness, there is also the option of adding a flare cut stop near the camera, though you probably won't need it.)

--Chris

[NewForestTel]

Thanks Chris and Thanks Pau for your help. As always, it is much appreciated.
I will report back when I have resolved these items.
Thanks again
Terry

[ChrisR]

Have a look for the material which Blue Peter used to call "Sticky backed Plastic", often "Fablon" make, which does come in a felt black.
I've had some for many years. It's is OK for most purposes though not quite as dead as Protostar.
I see one can buy 45cm x 5m for £25 - a lifetime's supply, but it would be worth checking a sample first in case they made it shiny.
1m lengths seem to be about £9.

Artists' Black paper, is often "good enough".

The Aktar material reminds me of looking at graphene - a totally black thing!

[NewForestTel]

Thanks Chris

I have now ordered some Black flocking paper (adhesive) from Edmund Optics - not too expensive £15 for two large sheets (20" x 30").
When I have fitted it to my extension tubes I will report back and let everyone know how it functions.
Thanks for your patience with me.
Terry