The Perfect Test Target

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RobertOToole
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The Perfect Test Target

Post by RobertOToole »

One factor thats tends to keep me from shooting lens tests is the target.
I've tried using natural targets like butterfly wings but they only meet one requirement from my list, details. Microscope targets like some from Thorlabs look great but cost hundreds of dollars. Used resolution targets on Ebay cost about $100 or less but the quality is unknown, some look pretty poor.

I few things I am looking for in a target:

-Target should be flat as possible.
-Clean and free from dirt, new would be ideal or at least easy to clean.
-Varied details with lots of fine level detail.
-Target should be able to last without degrading.
-Low cost.

I stumbled on a Silicon wafer on Ebay and took a chance.

Flat. Super fine details. New looking. Easy to clean. Lasts forever. $7.

Image

Wafer at just over 1X

Image

100% center crop
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100% lower right extreme corner

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100% lower left extreme corner

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100% upper left extreme corner

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100% upper right extreme corner

Image

Single image. Nikon D810. Scanner Nikkor lens 1.1X. Single Nikon SB-R200 flash. ISO 64. Nikon MM-11 stand.

Wafer source: Ebay item 262635273324

Let me know if you decide to try one and share an example.

Thanks for looking.

Robert

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Post by rjlittlefield »

The images look great! (Thanks for reminding me that nobody bought me any of these for Christmas last year like I asked for. Sniffle... But problem solved, I just now ordered some for myself.)

We've discussed these for targets in the past, mostly in the context of some sort of standardized target that could be used by different people at different places. The eBay offerings are not so great for that because it's a bit challenging to get the same thing twice.

The other issue is that mirrorlike surfaces tend to make illumination critical. See for example the discussion at http://www.photomacrography.net/forum/v ... 881#204881 and in the surrounding thread. I notice that your description here says "Single Nikon SB-R200 flash". I'm thinking there was quite a bit of diffusion involved, and I'm curious whether the appearance of this target changes much depending on how you light it. Have you run any experiments about that?

--Rik

Lou Jost
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Post by Lou Jost »

That's an attractive idea. I still have a soft spot for butterfly wings, though, particularly those with lots of long white scales on their margins, because these show the presence of LoCA. A perfectly flat target doesn't do that very well. My preferred standard is a wing of Vanessa cardui or its close relatives-- cosmopolitan, repeatable, free, and probably flying around in everybody's yards at least during the summer.

RobertOToole
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Post by RobertOToole »

Lou Jost wrote:That's an attractive idea. I still have a soft spot for butterfly wings, though, particularly those with lots of long white scales on their margins, because these show the presence of LoCA. A perfectly flat target doesn't do that very well. My preferred standard is a wing of Vanessa cardui or its close relatives-- cosmopolitan, repeatable, free, and probably flying around in everybody's yards at least during the summer.
Hi Lou,

B-fly wings are best for aesthetics but they can make a frustrating target. A few weeks ago I was going through a comparison of three lenses and about half-way through the second lens and without touching the wing once, it curled just a little but enough to make the comparison, not so much of a comparison.

I can only guess it warmed up?

Robert

RobertOToole
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Post by RobertOToole »

rjlittlefield wrote:The images look great! (Thanks for reminding me that nobody bought me any of these for Christmas last year like I asked for. Sniffle... But problem solved, I just now ordered some for myself.)

We've discussed these for targets in the past, mostly in the context of some sort of standardized target that could be used by different people at different places. The eBay offerings are not so great for that because it's a bit challenging to get the same thing twice.
I was just talking about that today with someone, that would be a really useful!
rjlittlefield wrote:The other issue is that mirrorlike surfaces tend to make illumination critical. See for example the discussion at http://www.photomacrography.net/forum/v ... 881#204881 and in the surrounding thread.
I did catch that thread, that was interesting.
rjlittlefield wrote:I notice that your description here says "Single Nikon SB-R200 flash". I'm thinking there was quite a bit of diffusion involved, and I'm curious whether the appearance of this target changes much depending on how you light it. Have you run any experiments about that?
Yes and I am still working trying to see what looks best for two goals in mind.

One for consistency like the test images above and second to bring out the most colorful reflections possible.

Seems like so far a well diffused single light source has less reflections and tonal changes.

Also I did see a hot spot in the center of the frame with one lens, even though the lens had a deep hood. I grabbed two strips of flocking material and laid them along the frame edge. My guess worked, flare was gone. I am thinking of making a 5-6 inch disc with a rectangle cut out to use as a shroud if I have more problems with flare.

I suspect I will be experimenting with lights for awhile, I even tried a ringlight with a sheet of diffusion material, it was terrible!

Thanks for the comments guys.

Robert

Smokedaddy
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Post by Smokedaddy »

I've been messing with them as well. Also here's a Intel 80486DX2 CPU.

Image

Image

-JW:
Last edited by Smokedaddy on Thu Sep 07, 2017 9:45 am, edited 1 time in total.

mjkzz
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Post by mjkzz »

wow, awesome!

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Post by enricosavazzi »

For lower magnification, the photomasks used to make ICs are an alternative to wafers. Typically, photomasks contain one or a few chip patterns, and the image is stepped and projected multiple times on a semiconductor wafer. Also, photomasks are usually chrome-on-glass, and therefore more similar than finished wafers to standard resolution targets, and can be placed on a back-illuminated diffusing sheet (e.g. a paper sheet) for use as high-contrast test targets. One photomask is used at each fabrication step, so the pattern on a photomask is usually simpler than those visible on a typical finished wafer.

I can see only one photomask from the US and one set of 6 photomasks from Israel on eBay at the moment, but there might be alternative search expressions that I have missed.
Edit: searching for photomask -photo in Business, Office and Industrial gives several more hits, but most of them unrealistically expensive.

Also with photomasks, the problem remains that they are largely one-of-a-kind.

For multiple copies of the same chip to distribute to multiple users, you can look for diced wafers, where the wafer has been scored and broken into individual chips (usually still attached to an adhesive plastic backing). In most cases, the dies that are tested good are removed from the tape backing, while the defective ones are left. I can see a few diced wafers on eBay at the moment. Non-diced wafers are problematic to cut by manual scoring, and may easily shatter.

There are plenty of silicon wafers available from Russian sellers, but probably they are just plain wafers without any pattern, useless for this purpose.
--ES

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Post by ray_parkhurst »

During photolitho processing, the photoresist is exposed by stepping across the wafer and lighting one field at a time. Each field is typically 20x20mm, though this size is design dependent. This would be a nice size for our purposes...not quite large enough for use at 1:1, but fine for 2:1 on FF. A wafer could be sawn such that full fields are singulated, giving many identical examples. Two fields, or a 2x2 array, could also be sawn to give a larger target, but with fewer yielded per wafer.

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Post by Harald »

Hi there Robert,
What a great idea. Thanks for sharing!

Ebay, here I come 8)

Edit: Just spent 15$ on a silicon wafer... Looking forward to get it :D
Last edited by Harald on Thu Sep 07, 2017 1:00 pm, edited 2 times in total.
Kind Regards
Harald

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RobertOToole
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Post by RobertOToole »

Smokedaddy wrote:I've been messing with them as well. Also here's a Intel 80486DX2 CPU.

Image

Image

-JW:
Pretty awesome James, thanks for sharing that one.

Nice depth to the 'steps' in the circuits.

What are the very faint white streaks?

Robert

RobertOToole
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Post by RobertOToole »

Harald wrote:Hi there Robert,
What a great idea. Thanks for sharing!

Ebay, here I come 8)
Glad to help Harold.

There is a good seller in France you should look at, very easy to work with and has some very interesting items:

http://www.ebay.com/usr/aberco?_trksid=p2060353

Harald
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Post by Harald »

Just bought from him 8)
Kind Regards
Harald

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RobertOToole
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Post by RobertOToole »

Harald wrote:Just bought from him 8)
Hi Harold,

FYI. Just got a second shipment from the seller Aberco and one of the wafers, the best one of course, is scratched over the entire wafer, I couldn't find one clean spot to photograph.

He is trying to deny I have a case by saying he states "minor scratches due to handling possible" in the auction so I opened a not as described case with Ebay. He claims the wafers are "pristine" in the auction and the other disks be sent are spotless so I hope he will send a replacement. The damaged wafer is a really good one!

Anyway I hope your wafers arrive in good shape!

Robert

mawyatt
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Post by mawyatt »

Robert,

The wafer I got from Tim in Huntsville seems OK, although I've only eyeballed it with a magnifying glass. He did ship in a small box with a balsa wood plank and regular foam wrapping, so certainly possible to get some damage during shipping.

Best,

Mike

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