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

Lou Jost · Post by **Lou Jost** » Sun Feb 07, 2016 5:34 pm

Just a wild thought- polarizing the light with a cheap polarizer might reduce some of those internal reflections.

rjlittlefield · Post by **rjlittlefield** » Sun Feb 07, 2016 6:20 pm

Lou Jost wrote:Just a wild thought- polarizing the light with a cheap polarizer might reduce some of those internal reflections.

It can make a small improvement, but there are two reasons why a newbie should not pursue this line of attack.

The first reason is that it's not very effective. Polarizers work great if you have polarized illumination or planar surfaces to cross axes against. But with non-polarized illumination and curved surfaces, they don't do much. See HERE, panel #2, left column, for an illustration of what happens with non-polarized illumination and a curved subject. In that case the reflective surfaces are in front of the polarizer, but reflections behind it will be similarly unaffected.

In the second place, trying to kill the reflections by polarizing the light distracts attention and effort from other more general and effective ways to kill them: flocking and baffling.

If flocking and baffling were dead simple, perhaps that would not be a problem. But they're not. Sometimes even finding the problem can be tough. To directly observe the reflections you may have to get your eye exactly where the sensor would be, and for some reason that I don't understand, that seems to be a tough concept to really absorb. I've seen very experienced people look into the back of a bellows, say "I don't see any reflections", and not realize that the offending reflection was just being blocked from view given exactly where their eye happened to be. (There's a trick using a cell phone camera that can help here, but that's a topic for its own thread.)

Anyway, sorry for the long reply to your wild thought. I'm just interested in getting ctron out of the weeds as quickly as possible.

--Rik

Lou Jost · Post by **Lou Jost** » Sun Feb 07, 2016 7:11 pm

Thanks Rik, those were very interesting links.

ctron · Post by **ctron** » Mon Feb 08, 2016 4:29 am

Rik, thanks again for your response. My budget is limited, so I'll be looking at the cheaper objectives and tests with interest. If all goes as planned, an objective should be here in the next few days.

Chris, yes, the flare/ veil was quite significant and the black shiny paper has tamed it somewhat. I took a ride by my local Walmart yesterday and they had velvet, which I read that some folks were using with success, but the type they had was even more shiny than the paper. There were two items of interest though that I didn't pick up, but wondered if they might be suitable:

1) Black sandpaper found in the auto section. When someone earlier, and I think it was Rik, said that the better flockers had a rough surface, I kept this in mind and it seemed the sandpaper did not reflect as much as the other things I came across.

2) Walmart does have effective 100% light blocking curtains. They are totally black and I actually use a couple in my photography dark room. I just didn't feel like spending $15 to cut away a tiny section for testing.

I'll keep the art shops in mind. Somewhat close are Michael's and a Hobby Lobby.

It's a real pity that I haven't been able to use the flashes since I'm getting the most flare from them, but I am having much more success with controlled constant lighting. Until the Ikea lights arrive, I've been using some CFL's with aluminum reflectors.

ChrisR · Post by **ChrisR** » Mon Feb 08, 2016 5:55 am

The stuff you're looking at in the picture
here http://photomacrography.net/forum/viewt ... 830#184830
is sticky-backed "velour", or something, from a range called "Fablon" inthe UK, which has wood grain etc. It's designed for the bottoms of abrasive posts and so on. It's not specifically designed for killing reflections. It's not as good as Protostar, but not bad. For this sort of "indirect" light reflection killing, it seems to be fine.
Searching on "black velour sticky" will find it.

"Sand" paper isn't something I'd be keen to put anywhere near the inside of a camera, and wouldn't individual grains be reflective?

I don't see why flash should be more inclined to cause flare than other light - it's what you do with it!

Again,, black paper baffles can be very effective.
You want the yellow light, you don't want the red rays
the blue baffles stop it.
Strictly the holes should be rounded rectangles, more circular near the lens, and a rectangle near the sensor, but a circle will help.

ctron · Post by **ctron** » Mon Feb 08, 2016 7:56 am

Chris, Thanks. I think you're referring to the internal macro tubes with your diagram. I may give it a try. Are there any set rules, or is it more just experimenting to find the baffle size and spacing?

ChrisR · Post by **ChrisR** » Mon Feb 08, 2016 9:39 am

I'd eyeball the rear of the assembly to look for reflections off sides, and then see where I could manage to get a ring to stay. You may only need one.

ctron · Post by **ctron** » Mon Feb 08, 2016 2:43 pm

rjlittlefield wrote:Adapters are sold by several sources on eBay. Mainly be aware that the threads are different for each of those objectives. For the CFI BE, you'll need an RMS adapter such as http://www.ebay.com/itm/New-8-X-36tpi-R ... 1209539132 or http://www.ebay.com/itm/RMS-8-microscop ... 0750438193, combined with an ordinary step ring to do 52mm-to-whatever as needed to fit each rear lens.

Objective on the way, but the real kicker is the RMS adapter as it looks like a China only item, so it may take a while to arrive. Isn't there a way I could just drill a hole in a lens cap and use that? Ideally, I'd thread the hole for the same size as the objective, but I'd probably have difficulty finding that size and pitch tap locally.

ChrisR · Post by **ChrisR** » Mon Feb 08, 2016 3:09 pm

It's been done! Rubber "O" rings each side of a cap can hold a lens.
Hot-melt glue is usable too. Blobs will hold, though they peel away from metal without leaving a mark

ctron · Post by **ctron** » Tue Feb 09, 2016 7:42 am

Well, after a LOT of searching, I managed to locate some workaround adapters found here in the US. I'm amazed that no one US based seems to carry the native RMS to 52mm adapters! The closest I could find was RMS to M42 (and even that took some searching to find at a *reasonable* price) and then an adapter to step up from M42 to 58mm lens size. I still could NOT find an M42 to M49 US based adapter, however.

I'm not trying to knock China, but the last time I ordered something it took 6-8 weeks to arrive and that was not long ago. I even had to inquire to the company to put a tracer on the item.

So... still looking to step up the male M42 threads to male M49, so if anyone knows a US based firm carrying one at good price, please share (technically, this would be female M42 to male M49)!

ChrisR · Post by **ChrisR** » Tue Feb 09, 2016 11:29 am

It's always camera first, so that would be called a Step-DOWN.

If you buy from Hong Kong rather than mainland China, things are often quicker (to the UK anyway).

ctron · Post by **ctron** » Tue Feb 09, 2016 12:44 pm

Thanks for that useful info, Chris. Well, assuming I used US suppliers that currently have the adapters in stock, and I'm pretty sure that they do from my research, I should be set up to go for 10x with my one telephoto by week's end. The other smaller telephoto I had hope to start with with 49mm threaded end I guess will have to wait for the adapters to arrive (had no choice but to go with China). I thought about the lens cap idea, but I don't have a press and could easily drill the holes with misalignment. I get the feeling that the objective alignment with main telephoto has to be quite precise.

Pau · Post by **Pau** » Tue Feb 09, 2016 1:33 pm

Many Chinese sellers offer faster post paying, the free post is really slow, I also think that Hong Kong is usually faster than continental China

ctron · Post by **ctron** » Tue Feb 09, 2016 7:54 pm

Attached are my latest results for earlier today. I'm also posting the set up. There's the red Pentax KX DSLR with reversed 18-55mm kit lens set at 18mm on 215mm macro tubes. This gives roughly 7.5:1 according to direct measurment.

Despite all efforts and using research from here and other sources, I still seem to still have contrast/ sharpness difficulties with this lens. I'm beginning to think that the lens itself, being a "kit" zoom lens with a lot of internal elements, might just not be up to the macro task at this 7.5:1 level.

Today's diffuser consisted of two styrofoam bowels, one inverted on top of the other, with a cutout for the lens on the one side as shown. The flashes were then placed as shown, nearly touching the bowls. I still had to use nearly 3/4 power on one flash and 1/2 on the other to get a decent histogram to show on the camera, and even then the part of the ant I really want to stand out, the face, which is perpendicular to the lens, still ends up darker than the rest of the body. I really try to stay at 100ISO, and more than that and I'm seeing noise after stacking.

The stacked result shows some errors and I see smoothness on the ant's underside. I think it has something to do with less light reaching that area, but not sure how to compensate with the flashes as they are.

I see people using a single flash for macro as shown in a couple of example images last week. I tried the flash aimed at a styrofoam plate overhead and then directed so the light bounced onto the ant, but the result was so dim I couldn't get it to work. I tried having the aperture fully open today and this did ease the stress on the flashes somewhat, but not nearly as sharp as where I currently have the lens stopped down (which I estimate is f/8-10).

The two bowls are about as close as I can get to the "tennis ball" diffuser at the moment, but I still don't think I have things working too well with so much flash power being used.

Anyway, once the objective arrives, I'm curious to see how many of these issues become irrelevant with the objective being so much sharper and no apparent contrast difficulties.

Invite comments/ suggestions as you have been doing all along, along with other things I could try with the set up.

rjlittlefield · Post by **rjlittlefield** » Tue Feb 09, 2016 8:09 pm

If your lens is sharpest when set at f/8-10, then that lens sucks for this application. At 7.5X achieved by extension, a nominal setting of f/8-10 on the lens will be f/68-85 on the camera side. (Effective = (mag+1)*nominal.)

On an APS-C sensor, that is so deep into diffraction territory that nothing you do will make the image look sharp, short of downsizing it by 5X or so.

It looks to me like you're still getting a central hot spot. What are you currently using to control stray reflections?

--Rik