Why You Need To Diffuse Jansjos

Sorry but this is just not axial. Axial lighting comes straight down onto the coin, perpendicular to the coin and parallel to the axis of the lens, which is why it is called "axial". A common way to do axial lighting in microscope systems is to have the prism or beamsplitter between the lens and camera (or eyepieces) and shine light down through the lens. This guarantees perfect axial alignment.

What you are showing, which is similar to what I showed in my beamsplitter-illuminated Lincoln Cent image, is a combination of axial and non-axial lighting. There is light hitting the coin that is coming from non-axial angles.

Separately, I am concerned about the cup you are using to ensure no direct light hits from the LED panel. I see that you have carefully black-out the rest of your setup, but not the inside of the cup! Light that reflects from the coin or hits the inner surfaces of the cup will re-reflect back onto the coin and cause light to hit the coin from very low angles. If this is your intent, then no worries, but it is another indicator of non-axial lighting.

To show you what "true" axial lighting looks like, I took a picture of the same coin as before but with the light only coming from the axis of the lens. Only the flat surfaces are reflected back to the lens with true axial technique. Any angled surface reflects the light away from the lens, and appears dark.

Laid up with Gout has given me the time to carry out some work to show my shots are Axial lighting. rmpsrmps seems to think they are not but he hasn't stated why he believes they are not. Assuming his hypothesis is right all I have to do to disprove my claim is to eliminate all extraneous light sources. The first possible fault in my last set of photos is the blue cup I used as a Shroud theres a chance( very slim IMHO) it might have been acting as a diffuser. So I covered it inside and out with black insulation tape. As below:




Now how to control the ambient light in the room and prove its been controlled? Some more black insulation tape and some surgery on a cardboard box!




Now perhaps when using the "shroud" I was mounting the coin too high so lets get rid of that Microscope objective tube. I just place the coin on the copy stand base board




Then we need a reference shot. Here is a quick photograph ( I blew it slightly as the coin is sitting on that objective tube). This is what the Prager Groschen looks like under direct lighting:




NOw before the first axial coin shot place the Shroud over the coin. You can't see the coin is this shot but you can see how well that shroud blocks light from getting down to the base board:




Then put the beam splitter in place then the modified cardboard box To make sure I didn't damage the beam splitter I changed to a "longer" lens; Olympus Zuiko 135mm F 4.5 bellows lens.




The first result that prager Groschen.....



looks different in comparison to the reference shot....but pretty much like the other two shots I claim are axial. Now what about the shadows on the left hand side of the field....the shroud is conical in shape and slightly higher on that side....those shadows are cast from the narrow part of the shroud. There were similar shadows on the right hand side but they weren't in the lenses field of view

Not every one will know what a 500-600 year old coin looks like under axial lighting. So lets return to that Liberty $20.00( like the prager Groschen its sitting on the base board of the copy stand:



Looks like axial lighting to me. It is actually a much better shot than the first one. I does prove that Rmpsrmps was partially right it wasn' 100% axial the first time. Perhaps I read him wrong but I was pretty sure he thought axial lighting was the minimum component.....I disagree axial lighting in the first shot was probably greater than 60% of all the light involved in the shot. In a Home studio situation its a bit hard to get only axial light. There will always be some reflection from else where but to claim the pictures weren't axial just stunned me!

I collect larger sized coins I don't have much copper and rmpsrmps is most familiar with copper( from what I have seen( I could be wrong) so how about a copper coin and one more reference shot.....I turrned off the Led Light source and left the beam splitter in place. I was surprised to get an image:



Yep with even all that work and the card board box some light is still getting in but turn on the LED light and:




At a guesstimate around 90 % axial lighting

Now go back to rmpsrmps's penny shots.....look at the dark rims......that why I don't think axial lighting and Janscos go together...the lighting source is just too small

Now you know why I recommend small bulbs or small mirrors for axial lighting. Maybe a circular cutout in black construction paper. Any light which does not hit the beamsplitter directly above the coin is a potential problem.

You could use a very distant light source to get perfectly axial light, but the point isn't to get a "perfect" axial lighting setup. It's to get attractive coin pictures.

rmpsrmps. You sell macro photography rigs so to improve your credibility you must seem more technical.... My impression is now that rather than admit you were wrong you are now going to use every argument in the book to prove your right no matter what was done. Your diagram is a perfect example of that. It is only half the story. You know very well you need to draw in the light path that travels through the beam splitter, passes through the lens and hits the sensor. That missing part of the diagram makes what you saying a half truth. Add in the missing light path and it is clear much more of the true axial light gets to the camera sensor while more of the diverging light does not.

You haven't looked clearly at my set up and no matter what I do You will have to make comment to show you are right. In my usual axial set up with out the shrouding there is no way diverging light from the light source can get to the subject. The only way it can get to the subject is via the beam splitter. The shroud just proved it it didn't enhance the system. you claim you have an axial light set up lets see how perfect it is Other wise don't call it axial lighting (Your words not mine) I will leave you and your cronies in this forum to it I will now get my advice from the photomacrography website. At least there I get proper explanations in plain language ( that quite often contradict what is said here SSuperdave You will be glad I have bowed out as now you can just form your opinions with out always taking the opposite view to mine( yes that is very much the impression I have gained. Neither of you have tried the type of light source I have been talking about and you only appeare to use Janscos..I a light I find useless for any coin of half dollear size or greater( the lagest medal I want to image is 105mm SSuper dave how in the world would a Jansco work for that?

Janco's usually produce a focused light ( hence the image at the start of the thread) and it has to be defocused by use of a diffuser. The other way round that( my method is to use multiple unfocused point sources) Its not perfect every so often I will get an overlaid image of the individual LEDs forming on the beam splitter...I usually just have to dim the LED panel( it has a dimmer control or move it backwards so the light doesn't focus on the beam splitter. RMPS I leave you to your sales pitches

I wouldn't use a Janso for axial lighting. Too small and too weak. I use 100w incandescents for axial. It presents a much larger light front which I can then use as much of as I need by the amount I allow to hit the beamsplitter, whether that means directing it through a paper aperture the size of the coin or not.

In any other usage all you have to do is increase the distance between bulb and subject. Jansjos throw a conical pattern. Make the cone the right size.

But the important thing - at least it's seemed intuitively obvious to me all along - is to inhibit any light beside that which directly contacts the coin.