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

[ctron]

Hi Rik,

First off, I admire you for sticking with me on this. You certainly have patience, probably more than I do

The first thing I did today was carefully tear open one of the Vivitars while having the manual handy. Unfortunately, inconclusive results as to why they are behaving erratically, so I reassembled it while staying well clear of the capacitor. So... I'm going to order another Vivitar for cheap price plus one of the flashes that Lou recommended.

I've been researching constant lighting too, with people having apparent success with some small Ikea work lamps, ordered a couple of those but they won't be here for days.

I will definitely take a look at the inverted cone you suggest too, definitely have to do something I think. I also think I need to place flocking? paper inside of the tube extensions.

I have the DigiFlash 3000. It was specified for Nikon or Canon, but a built-in slave allows me to use off camera and it is triggered by the Pentax. I had hoped someone, somewhere had come up with a variable power mod for it, but googling turned up nothing. I may try it out again today, but I'll be returning it soon as I don't think it's going to last much longer.

[rjlittlefield]

Patience, yep, got that...

Continuous lighting works OK, assuming you can keep vibrations under control and don't have too much problem with warm pixels. Be sure to use mirror lockup if you can.

I can't find an online manual for the DigiFlash 3000. What documentation I can find suggests that it's designed to be controlled entirely by the camera. It seems odd that they included a built-in optical slave without also providing a power control. I'm having trouble thinking of a good use for that combination, and omitting the feature would have saved some pennies in fabrication cost.

--Rik

[ctron]

I'm attaching the image I took earlier today. Rik, I tried the lens hood, but it didn't seem to make any difference. What did make a difference was stopping down the aperture more. Unfortunately, with the Pentax kit lens in reverse, the only way to adjust is by moving the aperture lever on the same side as the reverse side of the lens, which is now the front of course. There's a space created as the lever is adjusted and I've been stacking toothpicks to increase/ decrease aperture. If anyone knows of a better way, please share. I plan to do as I saw in your other post Rik (the lens hood page where you did lens comparison at different apertures) to try and determine which aperture produces the best sharpness in this kit lens. Just by going from nearly wide open to maybe f/11? has increased sharpness. The last two days, I was actually getting blurry results nearly wide open and it certainly will profit to do the f tests.

For this image, I stopped down by removing one of the toothpicks. I still had the image away from the histogram ends on both sides, but it wasn't as bad as wide open and easier to process because the stacks were sharper. the is the "map" image from Zerene, the first time I've gotten a map with less distortion although obviously still present probably due to the rough background and still much dust on the CCD. I brought out another 4 lamp CFL assembly and placed one assembly on each side of the specimen. The light is already pretty soft due to the nature of the bulb, so happy about that. Exposures were 1/10 sec @ ISO100. Roughly 30 images stacked.

[ctron]

I believe I finally determined the lens "sweet spot" last night. Without any "toothpicks" in place, lens was fully open and as I would insert toothpicks, aperture would close slightly each time. I would then take an image after each insertion. This was a crude way to go about it, but I couldn't think of any other way. Anyway, I determined that stopping down just slightly (one toothpick... so I'm assuming f/7-8... on an /3.5-22 kit lens... 4 toothpicks meant fully closed f/22) produced the sharpest image, so this is where I will keep the camera. Thanks for the aperture check idea, Rik, wasn't thinking of this right away until I read your post on the flare cone, but surely will save me a lot of time in post processing.

One thing I'm now seeing is that I think my lens sharpness on the extension tubes with optimal aperture has reached its limit. I'll see if the flashes I have coming (all my Vivitars are now non-functional) will rule out any shakes I would have been getting under constant lighting, but I don't think I'll reach the level of sharpness I see in others images here and web-wide. So, I am thinking of another lens.

I've been debating between either a microscope objective or enlarger/ microfische lens as I can't afford both. The sizes of ant I've been posting are about where I want the magnification (where you can see quite a lot of details on the head/body but they aren't filling the frame). At first, microscope objective, but I wanted to be able to maybe head outdoors with the set up too. Just for reference, the Pentax 18-55mm kit lens is currently reversed on 55mm macro tubes and set at 18mm. The Otamat 20mm has been one I've been considering, but inconsistent reviews hold me back.

[rjlittlefield]

For getting a sharp photo of an ant head, I recommend going with a 10X objective. A new one with known good performance can be purchased for around $100 if you're willing to live with short working distance. That would be the Nikon CFI BE, part number MRN70100, WD 6.7 mm, as illustrated in the thread at http://www.photomacrography.net/forum/v ... hp?t=16348. There are other objectives with much larger working distances, but the price rises steeply. The "gold standard" is the Mitutoyo M Plan Apo, with 33.5 mm working distance and list price $885.

I think you will not be happy trying to photograph in the field with any lens as sharp as a 10X microscope objective. The DOF will be approximately 0.01 mm so trying to get it placed properly would be mostly luck, and even when you succeed, most of the ant's head will be barely recognizable blur. See the fruit fly head HERE to see what I mean. Shooting ants in the field calls for sacrificing sharpness in favor of DOF and single-shot live action.

On an APS-C size sensor, the Nikon CFI BE objective (and a few others) can be pushed down to around 5X by using them with a rear lens that is shorter than the 200 mm that gives to get the nominal 10X. If you need lower magnification than that, then the next step down would be to 4-5X in microscope objectives, or a microfiche lens. The big difficulty with microfiche lenses is that some of them work really well, others not so much, and it's hard to find an exact model that has been tested. For microscope objectives and other lenses in the 4-5X range, there is some useful information at Lenses for use at 4-5X on an APS-sized sensor.

I don't recall what camera you're using. If it's full frame, then you have a lot less opportunity to push down the magnification of a microscope objective, because of coverage issues.

--Rik

[ctron]

Hi Rik,

Read your response here and to the other threads with interest. First off, I'd like to determine the actual mag ratio of my Pentax set up: reversed kit lens at 18mm estimate f/9 with 2.25" macro tubes. I'll measure it if I have to if cannot get an estimate mathematically.

I *really* like the idea of the Nikon objective with tube lens. Is it still available from SEO? What sort of mag could I expect with the two telephoto primes I have: 200mm f/4 SMC takumar and 135mm f/3.5 Zeiss Jenna?

I think the Nikon will be great for supplementing what I am already composing in the home here, but I'd like to set up something for "on the go" outdoors too. A week ago, I briefly tried out the 200mm Tak with a 50mm 1:2 Minolta reversed on front of it. I was able to capture a few ants through handheld and flash; results not great due to too high of f ratio, but then again I didn't think I'd get a reasonably clear ant at all so was surprised. Most insects I'd capture outdoors would probably be a lot larger than ants. Maybe I could find the sweet spot for this set up as well, or use a better outdoor lens to begin with.

[rjlittlefield]

I'll measure it if I have to if cannot get an estimate mathematically.

Just measure it. Photograph a ruler and do the arithmetic: sensor width divided by field width.

Calculations with a reversed and extended zoom lens are notoriously inaccurate. They can be made accurate, but only by carefully measuring a couple of cases first and then using those numbers to calculate for other cases.

I *really* like the idea of the Nikon objective with tube lens. Is it still available from SEO? What sort of mag could I expect with the two telephoto primes I have: 200mm f/4 SMC takumar and 135mm f/3.5 Zeiss Jenna?

All of the 10X lenses that I routinely recommend are available new. The 10X MRN70100 and MRL00102 (discussed HERE) are both available from SEO. They give rated magnification when used with a 200 mm rear lens. For shorter and longer rear lenses, the final magnification scales in proportion to the focal length of the rear lens, so a 135 mm rear lens will give 6.75X.

--Rik

[ctron]

Rik,

Ok, measurements confirm 7.5:1. I suspected somewhere around this, but unsure. I can now get an idea of image sizes with, for example, the microscope objectives and resize existing images to get a rough idea of how they'll appear. I started reading quite a bit of the discussion concerning the MRN70100 and MRL00102, but ran out of time and somehow I missed seeing the differences between the two you mentioned.

Edit: Never mind the question about Lightroom.

Thanks!

[ChrisR]

when in Photoshop, "0" feathering means the softest application of a tool

???

You're not thinking of Hardness??

[ctron]

when in Photoshop, "0" feathering means the softest application of a tool

???

You're not thinking of Hardness??

In my version of Lightroom, it seems I have to set feathering beyond 0 to get softer results, which is the opposite from Photoshop where the most feathering occurs at 0. I didn't realize this when I was trying Rik's suggested healing method, and then I was trying to go back, select all the healing spots I had created and then universally re-feather to 100. I decided to abandon doing it this way, just easier for me to use the "map" version Zerene produces and then heal/ clone the spots out on the final stack.

[ctron]

Allright, some more experimentation with my new Yongnuo flash today. As I feared, the center of lens flare (which I understand is called veil flare) returned, no matter where placed or what power. So, after already having the lens hood in place, it was time to remove the lens/ extension tube combination and I just wanted to see if placing a rolled up black paper cylinder inside the tubes as flush as possible to the lens would help. To my surprise, it did! The prominent center of lens flare with flash is gone BUT there is still a big lack of contrast throughout the images. I'm wondering if the paper is maybe the reason. All I had available was the large, black shiny sheets like you see at Walmart near the posterboards. I've just been cutting that and using it because it was handy. If it is the paper, what might work better? If I can source locally, that would be great, but if not, I'll order it.

[rjlittlefield]

The term I hear most often is "veiling glare". That refers to stray light that is so uniformly spread across the sensor that it's mostly perceived as a lack of contrast. See http://www.imatest.com/docs/veilingglare/ for further discussion.

The main difference between veiling glare and ordinary lens flare is just in the distribution of stray light. If the stray light remains as a recognizable though typically distorted ghost of a bright source, then it's usually not called "veiling", but if it's spread all over it is.

In addition to affecting the labeling, the distribution of stray light can give some strong clues about where it's coming from. Sharply defined ghosts are usually due to reflections between polished lens elements. There's not much you can do about those except to keep very bright lights from shining directly onto the front of the lens. The more spread out and fuzzy the stray light is, the more likely that it's reflecting from a less polished surface such as a lens mount or the inside of a tube. Those can be addressed by flocking and baffles. The central fuzzy hot spot you showed earlier is typical of reflections from tubes or mounts, which is why people mentioned to check that.

As for good flocking material, most paper is actually pretty shiny when viewed at glancing angles, which may be the situation inside your tubes. To get around that problem, standard flocking materials have a surface that is rough at the microscopic scale, so that most of the light that hits them is not at glancing angles.

One very popular material is "Protostar flocked light trap material". That stuff is known good and always available. If you're lucky, you may be able to locally source something similar or even better. For some hints about what to look for, see "Doodlebug cardstock is blacker than Protostar", which unfortunately describes a material that is no longer being manufactured.

--Rik

[ctron]

I think I'm going to go ahead on one of the Nikon objectives and work "backwards" from there. Rik, which would be the best out of the two you mentioned for 5-10x with either my 135 or 200mm standard telephoto lenses? It looks like I'd need an adapter in addition to the objective, any suggestions?

How useful would the objective be outside of the studio? Is the aperture adjustable at all (via the telephoto it would be but I don't know if that counts)? That might help with outdoor bugs and natural lighting at 5x on a mono or tripod (maybe I'm just dreaming here too).

Thanks!

[rjlittlefield]

Rik, which would be the best out of the two you mentioned for 5-10x with either my 135 or 200mm standard telephoto lenses?

It all depends on your budget.

If you can afford the Mitutoyo M Plan Apo than that's usually best because it has much less longitudinal color aberration (color shifts in out-of-focus regions). See http://www.photomacrography.net/forum/v ... 672#147672 and compare rows 2, 3, and 4 (different objectives, same tube lens).

If that's too rich, then between the two Nikons it is mostly a difference in working distance, 6.7 mm versus 10.5 mm. But both are quite short compared to what you're used to working with, and the difference in shape means that the extra WD does not make such a big different in lighting.

If you're strapped for cash, going with the cheaper Nikon CFI BE MRN70100 is a good decision. You can see at that URL given above that compared to the more expensive MRL00102, there's no significant loss in image quality. (Actually I think contrast is a bit better with the MRN70100. Its internal barrel design seems to be more resistant to reflections that can cause veiling glare.)

It looks like I'd need an adapter in addition to the objective, any suggestions?

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.

How useful would the objective be outside of the studio?

In my opinion, not very. Despite my legendary patience, I don't have nearly enough of it to mess with the framing and focusing requirements of a 10X objective in the field.

Is the aperture adjustable at all (via the telephoto it would be but I don't know if that counts)?

It doesn't work to stop down the telephoto. That just gives you vignetting.

Using a 10X NA 0.25 objective at rated magnification is already stopping down the rear lens to f/20. That's why images shot through an objective will not look as sharp as say a landscape shot at f/8.

It is possible to stop down an objective by interposing an iris between the objective and the rear lens. That is occasionally useful in bench work when focus stacking, mainly for the purpose of producing more recognizable though still very blurred background, while shooting most of the stack wide open to make the focused subject as sharp as possible. For non-stacked applications, its major effect is to reduce the resolution of the image to what you would get with more convenient optics.

--Rik

[ChrisR]

HA! Glad you finally tried and seen the problem!:D
It's a common one.
Often black paper from an Art materials shop is adequate. Another route to stop reflections getting to the sensor is to put one or more rings/discs (black paper, again) between lens and sensor. Exactly where, depends on the setup. If you make the hole in the middle only just big enough to pass the rays you need, the disc will stop ones which glance off the sides of the tube.