my first test with a telecentric lens - daisies

[dbur]

My first test with a telecentric lens. This uses a micro nikkor 55mm base lens on a Canon mount (50D) and Melles Griot telecentric lens. Four frames portrait with horizontal panning on a focus rail. Preprocessed with PhotoAcute and stitched with Hugin.

Shot at about f18 with a hand held flash covered by a paper towel.

I want to work up to focus stacks and quad resolution enhancement with PhotoAcute combined with the telecentric lens setup as I can get to it.

Any comments or suggestions? Thanks.

[elf]

The results look promising. Can you post more details about the telecentric lens and how the lens combination is assembled?

[Bob^3]

Dbur, I have an Invaritar P/N 59 LGA 499 telecentric lens made by Melles Griot (I picked it up for $5 a local camera swap meet, a while back---neither the vendor or I knew what it was!). Is this similar to your model?

I haven't fully tested it yet, but I found some info on the MG site that it is intended for use on a 100mm base lens. Perhaps it's a coincidence, but it happens to have 52mm threads and screws right on to my 105mm Micro-Nikkors, at a perfect distance for optimum telecentric effect.

Initial tests show that it doesn't fully cover the FX sensor in my Nikon D700 (severely soft edges and corners), at least at lower mag ranges. But it seems to do well on my smaller D200 sensor (not critically tested,yet).

I have the same goal as you to stack and stitch 2x2 mosaics to achieve higher resolutions for certain images that I would like to print at large sizes. However, I'm concerned at the possible loss of image quality from adding the extra optics, which if too severe may actually result in lower resolution final images.

I’d be very interested in knowing your results as your tests progress; and I'll post mine. Or if anyone else here is familiar with the telecentric lenses from Melles Griot?

Bob

[dbur]

Dbur, I have an Invaritar P/N 59 LGA 499 telecentric lens made by Melles Griot (I picked it up for $5 a local camera swap meet, a while back---neither the vendor or I knew what it was!). Is this similar to your model?

Bob

Mine is a 59 LGH 416. These go for $685 new so you got an awesome deal, though I haven't found what a 59LGA499 is on their site. In my opinion the Melles Griot site sucks. It's a pain to find anything. Here's a data sheet I found though it doesn't have your #. Maybe you could post a picture of it and I could see how it compares to mine. (or just check the pdf on the site below)

http://www.cvimellesgriot.com/Products/ ... enses.aspx

Click on the downloads tab and get the pdf.

I also found this:

http://www.retrevo.com/samples/Navitar-manuals.html

If you didn't get a lens cap an 82mm works for mine for the front and a 42mm for the back (there are inside threads as well). I got these for about $2 ea on ebay.

[dbur]

The results look promising. Can you post more details about the telecentric lens and how the lens combination is assembled?

See the previous post for a link to the only data I have on the lens. Here is a photo of it attached to the base lens.

Well dang the picture is not there after I upload it.

Try this:

http://www.flickr.com/photos/47889673@N07/4732535550/

[rjlittlefield]

Well dang the picture is not there after I upload it.

dbur, the upload panel requires that you click "just so" in order to get the url of your uploaded image inserted into your posting. Typically you will have to scroll to the bottom of the upload panel and click on either "insert picture: standard" or "insert picture and upload another one". Otherwise you will have uploaded the image but the posting won't reference it so you won't see it.

See the Image Hosting Steps for more information.

--Rik

[dbur]

Well I did all that but each time I looked at the upload gallery my old uploads were there but not the new one, even though it did seem to respond as if the upload was successful. Maybe my isp just sucks too bad.

Note that though the upload window completed with 'done' status, it did not open up a preview window to the image. The image is just a simple 116kB jpg.


I just tried again and it still didn't work.

[Bob^3]

Bob^3 wrote:
Dbur, I have an Invaritar P/N 59 LGA 499 telecentric lens made by Melles Griot (I picked it up for $5 a local camera swap meet, a while back---neither the vendor or I knew what it was!). Is this similar to your model?

Bob

Mine is a 59 LGH 416. These go for $685 new so you got an awesome deal, though I haven't found what a 59LGA499 is on their site. In my opinion the Melles Griot site sucks. It's a pain to find anything. Here's a data sheet I found though it doesn't have your #. Maybe you could post a picture of it and I could see how it compares to mine. (or just check the pdf on the site below)

I actually gave the wrong PN. The one I gave is for the extension ring on the assembly. The PN on the optical section is 59 LGF 410. But you won’t find that on their terrible site either. Here’s a photo of one for sale (about half way down the page):

http://www.andrewsmachine.com/optical_lumonics.html

It was several months ago when I bought this lens and researched it. Am now recalling that the major issue for use on a DSLR is that they all seem to be intended for covering only machine vision (video) cameras that have very small sensor dimensions. If you look at the pdf you linked to, even with “wide field” units like your LGA 499, although the column heading states a 1” sensor (probably diagonal), the footnote states that the field sizes are based on a 9.2mm x 9.2mm Kodak sensor. And since I believe telecentric optics are restricted to parallel light rays passing through the lens system, there may not be any way to increase the sensor coverage on these units to match your Canon D50 or my D200. So I think we both need to do some more critical testing of the edges of the field---or we may need to get cameras with tiny, high-res sensors in order to effectively use these interesting lenses for stack and stitch!

Bob

[rjlittlefield]

Well I did all that but each time I looked at the upload gallery my old uploads were there but not the new one, even though it did seem to respond as if the upload was successful. Maybe my isp just sucks too bad

I doubt that your isp could cause that problem, but our hosting isp has done it a couple of times lately. I now suspect that you got caught by one of the incidents discussed HERE.

--Rik

[rjlittlefield]

And since I believe telecentric optics are restricted to parallel light rays passing through the lens system, there may not be any way to increase the sensor coverage on these units to match your Canon D50 or my D200. So I think we both need to do some more critical testing of the edges of the field---or we may need to get cameras with tiny, high-res sensors in order to effectively use these interesting lenses for stack and stitch!

It's more like "parallel cones" than "parallel light rays". A telecentric lens admits cones of light just like a regular lens does. The difference is that with a normal lens, the central axes of the cones diverge radially from the center of the entrance pupil, while with a telecentric lens the central axes of the cones are all parallel to each other. This is equivalent to saying that "the entrance pupil is at infinity".

In order for the entrance cones to be parallel, the front lens element must be as large as the subject field plus the diameter of each cone as it enters the lens.

As a result, telecentric lenses cannot have a large field of view unless their front element is correspondingly large.

The meaningful sensor size is only as big as the field of view times the magnification, so the natural pairing is for small sensors at low magnification with reasonably sized lenses.

If you put the lens on some extension to get more magnification, then it will cover a larger sensor, but the size of the telecentric field will stubbornly stay fixed by lens diameter and cone width. Trying to cover a larger field results in losing telecentricity away from image center. See http://www.edmundoptics.com/technical-s ... ic-lenses/ for some illustration of this.

--Rik

[dbur]

I have a few extension sections that go between the lenses. I tried some but it seems the best is with no extensions using my micro nikkor 55mm base lens. I do get a full image on the 1.6 crop factor lens in my Canon 50D. How close to telecentric over than span it is probably needs more testing.

Here is a test shot: I have two identical bolts and a penny on edge. The right bolt is at 2.625" from the front of the lens, the penny is at 4.125" and the left bolt is at 6.125". I focused on the penny and set the f to 32. The base lens focus setting is at 1.25 ft. This is the full frame, no cropping. Still not quite enough depth for that range, but I guess that's not what we're looking for here, and it is good enough to see the effect. Both bolts look ~ the same size.



Hey, the upload is working again!

[Bob^3]

I tried some but it seems the best is with no extensions using my micro nikkor 55mm base lens.

That's what I'm finding too with longer extensions between the lenses using my 105mm Micro-nikkor. However, my Invaritar had a short (15mm) extension tube on the mounting side when purchased. It will mount to the 105mm with or without this. But the combo works better with the tube.

Still not quite enough depth for that range, but I guess that's not what we're looking for here, and it is good enough to see the effect. Both bolts look ~ the same size.

I've also verified near perfect telecentric behavior in the same way as you have. However, I'm looking for more than this capability. I also need corner-to-corner sharpness similar to my 105mm used without the telecentric. If telecentricity comes at the cost of poor resolution, either at the edges or center of the frame or both, for my purposes it defeats the benefits of stack and stitch. Why go through the extra time and effort to capture multiple focus stacks and more post processing, if the final image has the same or less image quality as a single stack? My goal is having the option to make very large prints and to have extra (sharp) pixels for cropping the frame, if needed. But I realize your goals may be different.

I do get a full image on the 1.6 crop factor lens in my Canon 50D.

I also get a full 'image' on both full frame and cropped frame sensors (as in no vignetting). However, the image is clearly unusable at the edges of the D700 FX sensor with my combo---I can clearly see this by just looking through the viewfinder or with Live View. Visually, it’s appears much better in the D200 (DX) viewfinder. But I still need to compare images from the 105mm Micro-nikkor made both with and without the Invaritar to determine how much IQ is lost. I would certainly expect there is some loss in IQ at both the center and edges of the frame. Whether or not this trade-off is acceptable, I think depends on your intended application and your particular optical configuration. The comparison (with and without the Invaritar) is made more difficult by the fact that the Invaritar acts like adding a strong diopter added to the 105mm base lens, resulting in increased magnification and shorter working distance. I may compare it with one of my other flat-field lenses optimized for a similar magnification range.

If your intention is to obtain more usable image data in the final image by using stack and stitch, I think you should also take a critical look for possible image degradation from adding the Invaritar to your D50/55mm---if you haven’t already done so.

Bob

[dbur]

Good points.

I haven't done much more than you see here yet.

[Bob^3]

Understood dbur, neither have I. Please post any results with your optics combo and I'll do the same. My problem is I've got way too many hobbies. Someone in this forum posted a statement awhile back saying something like, when I started this project, I didn't realize my life expectancy might be a limiting factor!

[Bob^3]

It's more like "parallel cones" than "parallel light rays".

Will you never tire of correcting me Professor Littlefield? By that I mean please do not stop correcting me. As someone else stated recently, you are an outstanding teacher, sir. And in my brand of philosophy, truth trumps ego every time. I've met many people who have never learned that fact.

Thanks for the clarification on telecentric lenses. I've got more questions on this, as time permits.

Bob