New Mineral Named After GIA’s John Koivula
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 Post subject: Re: NA - R - DOF
PostPosted: Thu Oct 21, 2010 4:56 pm 
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Another hyper-realTM photographer! Conny, it'd be interesting to see that "Negative crystal in Quartz from Herkimer County filled with fluid and gas" shoot again under the more tedious scheme I suggest. Of course, that crystal might be too big to use max magnification. But the calculations are already set up... we can figure out what you need to do for whatever magnification and NA you are working with.


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 Post subject: Re: NA - R - DOF
PostPosted: Thu Oct 21, 2010 10:29 pm 
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FYI, pixels on a camera mean nothing anymore aside from a selling point. In reality the APS-C sensor topped out at about 8-10MP for optimal quality of the pixels on the sensor, talking common used Bayer sensor. As they increase them they actually lose quality in the pixels. The reason your Oly was a smaller sensor as it is a 4/3 sensor, not an APS-C, as most standard dSLRs are. The only time more pixels is a good thing now is if you step up to a FF(full frame) sensor or a MF(medium format) sensor cameras. I am anxiously awaiting the new Sigma SD1 46MP camera, it is supposed to be along the lines of a MF in image quality and DR, and if so and a reasonable price it will be my next camera; The Pentax MF digital was going to be, but I am not spending $10K on a camera body, lmao. At that price my K10D Pentax and Sigma SD9 & SD14(equivalent in resolution and image quality to a FF sensor camera like the Canon 5D) do the job just fine.

Tim, on your M42 adapter, I hope you made sure to get the one that allows for infinity focusing, some of the cheaper models do not allow it, I found that out the hard way when I bought my first one for my Canon. :(. Also be on the watch for the dreaded ERR 99. Canon has been having issues with this lately, it is a catch all error code. But it typically means one of three things in order of most common first.. 1. Contacts to lens on lens or body need cleaned(use an eraser)... 2. Shutter curtain failure(been having pre-mature shutter failures since the 40D... started with the 300D but then fixed.. but resurfaced since the 40D and has been problematic since)... 3. Lens malfunction. If cleaning contacts don't work get it into Canon service ASAP, not sure over the pond which one is best, over here in USA the California center is probably the best with the one on the east coast being horribly bad! You should like the video on it, AF can be a bit finicky at times, but VQ is quite nice.

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 Post subject: Re: NA - R - DOF
PostPosted: Fri Oct 22, 2010 1:28 am 
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Really good points Swishman. Even if Tim, Conny, and I are the only ones paying attention. Anyways, just more reason for Conny to not go out and spend the big bucks on a new camera.


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 Post subject: Re: NA - R - DOF
PostPosted: Sat Oct 23, 2010 4:34 am 
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Swish, I use the cheapest m42 lens mount adapter ring possible to hook up the bare camera body to the scope. I don't get your advice on making sure it allows me infinity focussing. I just shoot in manual mode, and all the focussing is done by the scope...


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 Post subject: Re: NA - R - DOF
PostPosted: Sat Oct 23, 2010 5:25 am 
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Hi Dr. Brian,

Brian wrote:
Even if Tim, Conny, and I are the only ones paying attention.


The fact that no one else posted here doesn't mean there's no folks lurking and reading..... i for me really enjoyed the exchanges of very useful infos.......i'm just in learning mode here....... :D The only thing i found weird Gene didn't jumped in, for what i know he should have more than a word to add to the discussion...... :roll:
thank you to everyone for the insights.
ciao
alberto

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 Post subject: Re: NA - R - DOF
PostPosted: Sat Oct 23, 2010 9:49 am 
Alberto wrote:
Hi Dr. Brian,

Brian wrote:
Even if Tim, Conny, and I are the only ones paying attention.


The fact that no one else posted here doesn't mean there's no folks lurking and reading..... i for me really enjoyed the exchanges of very useful infos.......i'm just in learning mode here....... :D The only thing i found weird Gene didn't jumped in, for what i know he should have more than a word to add to the discussion...... :roll:
thank you to everyone for the insights.
ciao
alberto


Yep, here's another lurker.....

All very good stuff even if of only academic interest to me for the time being. For the present, the problems I wrestle with are:

- A camera with insufficient dynamic range.
- A camera mounting which is non-rigid, meaning that there always some rotational displacement between similar shots.
- A manual shutter release with no forseeable chance to upgrade it with a remote release.
- Focussing has to be on a 3x4 in TFT screen that (in addition to the camera's poor dynamic range) seems to have too few pixels to allow for simple and quick critical focussing.

As I keep muttering to myself under my breath, 'It's a poor workman who blamed his tools'. And indeed, used within its limitations, this sub-300 buck camera does produce some quite acceptable results. However, for as long as I continue to use this camera, the stacking software that is stored on my hard drive must remain unpacked. To attempt to experimennt with it now could only be a waste of time I think.

However, I do find time spent lurking here to be thought-provoking and eventually it will prove useful I am sure. I also stored a link the other day to a paper that suggests that 10um resolution is within the reach when using an old Nikon CoolPix 990 camera for photo micrography. So hope springs eternal.


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 Post subject: Re: NA - R - DOF
PostPosted: Mon Nov 01, 2010 10:11 pm 
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I guess I am slipping. I only just noticed this thread today.

Back in the day, the microscopers' rule of thumb was to try and get something like
500 to 1000 times the numerical aperture magnification onto the film. So for
an M400 ApoZoom with the proper Apo 2x objective that is a magnification of 230x

Any more than that just results in so called "empty magnification" where no new detail is revealed. This thread has touched on many of the issues that come into play such as depth of field versus resolution (and now stacking) We used to consider whether we wanted to shoot it onto 4x5 film or 2 1/4x3 1/4 (6x9cm) 0r 35mm. The answer depended on whether it was color or black and white and whether it was for publication in a Journal or for enlargement say for a poster session. The bigger the film the longer the exposure had to be which made a difference on the ninth floor of a hospital that had train tracks in the basement. You considered how much additional enlargement might be made and made sure the film was fine grain enough to support that.


Similar considerations exist when trying to graft digital cameras onto microscopes. The camera makers like to have pixel count wars but we already know from spectroscopy that smaller pixels are not necessarily better. And there are some cameras as Jamey points out that can sample each pixel location in all three colors. To equal the performance of such cameras you essentially need to double the pixel count. That is a six megapixel camera that samples each color should equal a 12 megapixel Bayer pattern camera.


I have always told anyone who asked me that although there are many formulae that one can apply to try and get a first approximation of what will happen, ultimately you have to get your hands on the parts and assemble them and see what you get.

There are also some decisions that are difficult to make until you see them on your screen.

The main one of these is the following choice:

If you imagine the image circle that the M400 throws (Tim there is no optic above the prism. There Is a projective for each film format.) it is about 23 mm in diameter. If you project it without further magnification onto the sensor of your Full Format camera you will have a circular image and will have vignetting at the two long ends of the frame. You will capture the whole image that the scope throws and if you have enough pixels you may get all the resolution that the scope has available but you will be wasting some of the camera pixels and capacity.

So you can use a different projective and make the image circle larger than the chip. Or use a smaller chip (which might have smaller pixels) Imagine a larger image circle with the cameras' rectangle inscribed in it. So now the camera frame is filled but you are throwing away some of the microscopes field of view in order to light all the pixels to the edge.(of the cameras frame)

This is analogous to to the film size question we used to have to decide the answer to ,only it it goes in the other direction. Since bigger pixels have a better signal to noise ratio than smaller pixels, I would want a three shot camera with as big pixels as possible and as large a chip size as possible.

People usually have some camera they want to use, and a scope they want to use it with. The trick then is to get them mechanically mated together (ie. with a T mount or M42 mount or some other variant) and then also simultaneously optically mated by managing to get the correct projective into place. That part is often very difficult and tricky and I have not found a better more predictive way than to try it. The difference in the power of the projective lens is not much for the two examples above. One might be a 0.32x and another 0.70X So its nice to have a selection of projectives available.;

http://www.spotimaging.com/iq/couplercalculations.html
http://www.spotimaging.com/iq/couplercalculations2.html
http://www.spotimaging.com/techforum/Ju ... /index.htm
http://www.spotimaging.com/techforum/May_2002/index.htm
http://www.spotimaging.com/techforum/Sp ... sSep06.pdf
http://www.spotimaging.com/techforum/Ad ... rticle.pdf

The above articles have one of the most accurate description of the number of pixels needed and why, that I have run across on the web. It is better to over sample than to under sample. If you have too many pixels, or they are too small, you may be able to bin them either in the camera or in PhotoShop.


Last edited by G4Lab on Tue Nov 02, 2010 12:17 am, edited 4 times in total.

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 Post subject: Re: NA - R - DOF
PostPosted: Tue Nov 02, 2010 12:04 am 
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Jeez, I pretty much followed the first part of that (most of the things you guys discuss here goes right over my head but is intriguing just the same) but the second half was beyond me. Such a steep learning curve for an old silver nitrate buff.

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 Post subject: Re: NA - R - DOF
PostPosted: Tue Nov 02, 2010 1:12 am 
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So how useful would it be to have a "yardstick" to measure distance on the microscopic scale? That is to say, some microscopic material whose shape and size is known to very good precision, and that could be laid out on a microscope slide.


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 Post subject: Re: NA - R - DOF
PostPosted: Tue Nov 02, 2010 6:18 am 
Brian wrote:
So how useful would it be to have a "yardstick" to measure distance on the microscopic scale? That is to say, some microscopic material whose shape and size is known to very good precision, and that could be laid out on a microscope slide.


This the sort of thing you have in mind (0.01mm graduation)? Stage micrometer from Zarf Enterprises. USD 50.00. Sold for the purpose of eyepiece reticle calibration. Reticles also sold by Zarf.
Attachment:
3145stage%20micrometer.jpg
3145stage%20micrometer.jpg [ 34.84 KiB | Viewed 2507 times ]


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 Post subject: Re: NA - R - DOF
PostPosted: Tue Nov 02, 2010 9:48 am 
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Well, 1 mm is a bit larger than what I had in mind. And a flat lithographic image is not going to help much with depth of field.


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 Post subject: Re: NA - R - DOF
PostPosted: Tue Nov 02, 2010 10:33 am 
Brian wrote:
Well, 1 mm is a bit larger than what I had in mind. And a flat lithographic image is not going to help much with depth of field.


0.01mm? Two dimensional only, granted, and thus only useful for determination of resolution. Might a holographic image suit better with its inherently better resolution?


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 Post subject: Re: NA - R - DOF
PostPosted: Tue Nov 02, 2010 11:55 am 
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Kerensky wrote:
0.01mm?


Oh, it says 0.01 mm. I thought the 0.0 was two eyes and a nose. Yes, that is the size I had in mind.

Kerensky wrote:
Might a holographic image suit better with its inherently better resolution?


That statement is silly and nonsensical. I think you tossed out that made-up bit of pseudoscience as an intentional provocation.


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 Post subject: Re: NA - R - DOF
PostPosted: Tue Nov 02, 2010 12:06 pm 
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Light erasable PROM cheeps are used for that purpose all the time.


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 Post subject: Re: NA - R - DOF
PostPosted: Tue Nov 02, 2010 12:12 pm 
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que?


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