I just want to give an update of my attempts to use a Nikon D70 DSLR on a
trinocular viewing body (see my previous posts regarding this subject).

Using objectives that are fully corrected for lateral chromatic aberration
(no CDM), I found the following:

1) At fast exposure settings, the mirror slap of the D70 (no mirror lockup
feature!) only contributes to the already existing vibration induced by the
mechanical shutter curtain. I assume a D100 or D2H will not save the day. I
might still get vibrations due to the mechanical shutter.

2) At slow exposure settings using bulb mode, I get excellent images. They
are sharp and, of course, free from vibrations. Fast moving subjects can
easily be photographed with a flashlight moved into the illumination path as
long as a collector lens is added in front of the flash for proper Koehler
illumination.

3) The D70 can be connected to a regular eyepiece (with a spacer in front of
the eyepiece). The necessary spacer is around 5mm in length. With this
setup, which is parfocal with the objectives, the D70 oversamples the image
(too many pixels!). A relay lens (photo eyepiece) with a magnification
factor of 0.5x is recommended but such a relay lens can be rather expensive.

4) The D70 works great when its CCD is positioned into plane holding the
real image. In this case, vignetting occurs, but the D70 provides enough
pixels so that after cropping away the effect of vignetting a well-sampled
image remains of 3 to 4 Mpixels.

The 12-bit RAW file format with the larger pixels of the D70, make this
camera an interesting solution for amateur photomicrography. The D70 is very
strong for low light exposures. Remember, it is possible to combine this
digital camera with a scope with only a couple of lens-less adapters that
cost around US$80 to 100. Of course, this solution makes only sense for
people who are already enjoying using the D70 for photography :-)

Gregor

From:	Richard J Kinch
Subject:	Re: Nikon D70 DSLR on microscope: Update
Date:	Sun, 26 Dec 2004 01:02:53 -0600

GTO writes:

> I just want to give an update of my attempts to use a Nikon D70 DSLR
> on a trinocular viewing body (see my previous posts regarding this
> subject).

Interesting report, thanks.

What scope, magnification, eyepieces, etc., are involved?

http://www.truetex.com/micad.htm

From:	GTO
Subject:	Re: Nikon D70 DSLR on microscope: Update
Date:	Mon, 27 Dec 2004 23:58:45 GMT

Setup using an ocular:

1) The setup consisted of a Nikon E400 with 2x, 4x, 10x, 40x and 100x/oil
lens. A Y-T TV tube was connected to a trinocular viewing body to provide an
ISO 38mm port for a 1x C-mount adapter (with no lens). The eyepiece was a
Nikon MDC lens for which I got a M28 to C-mount adapter. A C-mount to
T-mount converter with two gender-changer did the trick.

2) Since the Ortholux has an ISO port and the Periplan ocular has a M28
thread, the connection of the D70 to the Ortholux worked just fine and is
very similar to the one mentioned above.

Setup using direct projection of real image onto CCD:

1) Same Nikon scope as mentioned above except no Nikon MDC lens and no 10mm
t-mount spacer. Also 1x C-mount adapter got directly mounted on the trinoc
port without the Y-T TV tube.

2) Not recommended for the Ortholux, since all my objectives require a
compensating eyepiece (or relay lens) to complete the correction for lateral
chromatic aberration.

If time permits, I will write up an article about this.

Gregor

"Richard J Kinch" wrote in message
news:Xns95CB14D4D9E5someconundrum@216.196.97.131...
> GTO writes:
>
>> I just want to give an update of my attempts to use a Nikon D70 DSLR
>> on a trinocular viewing body (see my previous posts regarding this
>> subject).
>
> Interesting report, thanks.
>
> What scope, magnification, eyepieces, etc., are involved?
>
> http://www.truetex.com/micad.htm

From:	KBob
Subject:	Re: Nikon D70 DSLR on microscope: Update
Date:	Tue, 28 Dec 2004 16:57:10 GMT

On Sun, 26 Dec 2004 05:18:10 GMT, "GTO"
wrote:

>I just want to give an update of my attempts to use a Nikon D70 DSLR on a
>trinocular viewing body (see my previous posts regarding this subject).
>
>
>
>Using objectives that are fully corrected for lateral chromatic aberration
>(no CDM), I found the following:
>
>
>
>1) At fast exposure settings, the mirror slap of the D70 (no mirror lockup
>feature!) only contributes to the already existing vibration induced by the
>mechanical shutter curtain. I assume a D100 or D2H will not save the day. I
>might still get vibrations due to the mechanical shutter.
>
>2) At slow exposure settings using bulb mode, I get excellent images. They
>are sharp and, of course, free from vibrations. Fast moving subjects can
>easily be photographed with a flashlight moved into the illumination path as
>long as a collector lens is added in front of the flash for proper Koehler
>illumination.
>
>3) The D70 can be connected to a regular eyepiece (with a spacer in front of
>the eyepiece). The necessary spacer is around 5mm in length. With this
>setup, which is parfocal with the objectives, the D70 oversamples the image
>(too many pixels!). A relay lens (photo eyepiece) with a magnification
>factor of 0.5x is recommended but such a relay lens can be rather expensive.
>
>4) The D70 works great when its CCD is positioned into plane holding the
>real image. In this case, vignetting occurs, but the D70 provides enough
>pixels so that after cropping away the effect of vignetting a well-sampled
>image remains of 3 to 4 Mpixels.
>
>
>
>The 12-bit RAW file format with the larger pixels of the D70, make this
>camera an interesting solution for amateur photomicrography. The D70 is very
>strong for low light exposures. Remember, it is possible to combine this
>digital camera with a scope with only a couple of lens-less adapters that
>cost around US$80 to 100. Of course, this solution makes only sense for
>people who are already enjoying using the D70 for photography :-)
>
>
>Gregor

Here's another idea. Someone on eBay has been selling microscope
adapters that contain 10X WF eyepiece lenses and they come in both
23mm size (for standard microscopes) and 30mm sizes to fit binocular
microscopes. These have 28mm male threads intended to couple with
Nikon Coolpix cameras. All that's needed to make these work with
other cameras (such as the D100, D70, etc.) I'm told is a 52-28mm
stepdown ring, also readily available. I ordered these and will post
shots after testing.

I've been trying to use a Nikon microscope adapter (containing relay
lens) with a Zeiss Standard microscope, but thus far the results
haven't been all that great, at least with top-illuminated subjects.
Loads of glare and chromatic aberration, and the photos look far worse
than the objects appear visually. I'm trying to shoot the irregular
surface of a silver amalgam filling, and the specular highlights from
the mercury specks (or something) is making this task difficult. Has
anyone tried anything like this?
Thanks, kBob

From:	GTO
Subject:	Re: Nikon D70 DSLR on microscope: Update
Date:	Tue, 28 Dec 2004 21:41:23 GMT

The problem with adapters that include eyepieces or relay lenses is the
possible mismatch between objectives and adapter lens.

A Nikon CF-based scope (Labophot, Optiphot, Eclipse) requires CF relay
lenses (or eyepieces). These are fully corrected for lateral chromatic
aberration but not over-corrected.

A scope like the Leitz Ortholux with Fluor or APO lenses requires
compensating relay lenses (or eyepieces) that are over-corrected for lateral
chromatic aberration.

This is particularly important if most of the image is captured by the CCD
and not just the rays close to the optical main axis of the system. A
low-cost setup to connect a DSLR to a scope should include existing optical
components and not add new ones that might lead to a mismatch in optical
correction. After all, I want to use a DSLR to go beyond the performance
offered by a consumer grade digital camera, such as the Nikon Coolpix or
Canon Powershot digicams.

Gregor

"KBob" wrote in message
news:0o33t09r3h5vkd7vtd5dk555jt9egdjhvq@4ax.com...
> On Sun, 26 Dec 2004 05:18:10 GMT, "GTO"
> wrote:
>
>>I just want to give an update of my attempts to use a Nikon D70 DSLR on a
>>trinocular viewing body (see my previous posts regarding this subject).
>>
>>
>>
>>Using objectives that are fully corrected for lateral chromatic aberration
>>(no CDM), I found the following:
>>
>>
>>
>>1) At fast exposure settings, the mirror slap of the D70 (no mirror lockup
>>feature!) only contributes to the already existing vibration induced by
>>the
>>mechanical shutter curtain. I assume a D100 or D2H will not save the day.
>>I
>>might still get vibrations due to the mechanical shutter.
>>
>>2) At slow exposure settings using bulb mode, I get excellent images. They
>>are sharp and, of course, free from vibrations. Fast moving subjects can
>>easily be photographed with a flashlight moved into the illumination path
>>as
>>long as a collector lens is added in front of the flash for proper Koehler
>>illumination.
>>
>>3) The D70 can be connected to a regular eyepiece (with a spacer in front
>>of
>>the eyepiece). The necessary spacer is around 5mm in length. With this
>>setup, which is parfocal with the objectives, the D70 oversamples the
>>image
>>(too many pixels!). A relay lens (photo eyepiece) with a magnification
>>factor of 0.5x is recommended but such a relay lens can be rather
>>expensive.
>>
>>4) The D70 works great when its CCD is positioned into plane holding the
>>real image. In this case, vignetting occurs, but the D70 provides enough
>>pixels so that after cropping away the effect of vignetting a well-sampled
>>image remains of 3 to 4 Mpixels.
>>
>>
>>
>>The 12-bit RAW file format with the larger pixels of the D70, make this
>>camera an interesting solution for amateur photomicrography. The D70 is
>>very
>>strong for low light exposures. Remember, it is possible to combine this
>>digital camera with a scope with only a couple of lens-less adapters that
>>cost around US$80 to 100. Of course, this solution makes only sense for
>>people who are already enjoying using the D70 for photography :-)
>>
>>
>>Gregor
>
> Here's another idea. Someone on eBay has been selling microscope
> adapters that contain 10X WF eyepiece lenses and they come in both
> 23mm size (for standard microscopes) and 30mm sizes to fit binocular
> microscopes. These have 28mm male threads intended to couple with
> Nikon Coolpix cameras. All that's needed to make these work with
> other cameras (such as the D100, D70, etc.) I'm told is a 52-28mm
> stepdown ring, also readily available. I ordered these and will post
> shots after testing.
>
> I've been trying to use a Nikon microscope adapter (containing relay
> lens) with a Zeiss Standard microscope, but thus far the results
> haven't been all that great, at least with top-illuminated subjects.
> Loads of glare and chromatic aberration, and the photos look far worse
> than the objects appear visually. I'm trying to shoot the irregular
> surface of a silver amalgam filling, and the specular highlights from
> the mercury specks (or something) is making this task difficult. Has
> anyone tried anything like this?
> Thanks, kBob
>
>

From:	Richard J Kinch
Subject:	Re: Nikon D70 DSLR on microscope: Update
Date:	Wed, 29 Dec 2004 00:34:03 -0600

KBob writes:

> Here's another idea. Someone on eBay has been selling microscope
> adapters that contain 10X WF eyepiece lenses and they come in both
> 23mm size (for standard microscopes) and 30mm sizes to fit binocular
> microscopes.

Can you post a link or item number for an example?

From:	Richard J Kinch
Subject:	Re: Nikon D70 DSLR on microscope: Update
Date:	Wed, 29 Dec 2004 00:33:13 -0600

KBob writes:

> I'm trying to shoot the irregular
> surface of a silver amalgam filling, and the specular highlights from
> the mercury specks (or something) is making this task difficult.

All digital cameras have very, very narrow dynamic range, compared to film.
Highly dynamic scenes like yours are a problem. You have groups of
entirely washed-out pixels, and surrounded by more pixels that are color-
aberrated.

This would seem to require some kind of non-linear optical filter to
correct (does that exist?).

From:	GTO
Subject:	Re: Nikon D70 DSLR on microscope: Update
Date:	Wed, 29 Dec 2004 07:29:09 GMT

The dynamic range of digital vs. film needs some clarification. A dedicated
microscopy camera with a 14 or even 16-bit A/D offers a comparable dynamic
range to the one of color negative film (up to 9 f-stops). The 12-bit A/D of
most digital cameras offers at least as much dynamic range as color slide
film (5 to 6 f-stops).

If an image feature causes bright reflections, proper episcopic illumination
with a polarizer can help a lot. I used a Nikon CF BD Plan 50x objective
with episcopic illumination to look at metal surfaces (such as coins)
without any problems even with a digital recording device with only 10-bit
A/D (http://geocities.com/gregor_o/USCoin03.jpg).

Gregor

"Richard J Kinch" wrote in message
news:Xns95CEFCBA5E41someconundrum@216.196.97.131...
> KBob writes:
>
>> I'm trying to shoot the irregular
>> surface of a silver amalgam filling, and the specular highlights from
>> the mercury specks (or something) is making this task difficult.
>
> All digital cameras have very, very narrow dynamic range, compared to
> film.
> Highly dynamic scenes like yours are a problem. You have groups of
> entirely washed-out pixels, and surrounded by more pixels that are color-
> aberrated.
>
> This would seem to require some kind of non-linear optical filter to
> correct (does that exist?).

From:	Richard J Kinch
Subject:	Re: Nikon D70 DSLR on microscope: Update
Date:	Wed, 29 Dec 2004 05:00:38 -0600

GTO writes:

> The dynamic range of digital vs. film needs some clarification. A
> dedicated microscopy camera with a 14 or even 16-bit A/D offers a
> comparable dynamic range to the one of color negative film (up to 9
> f-stops). The 12-bit A/D of most digital cameras offers at least as
> much dynamic range as color slide film (5 to 6 f-stops).

I don't follow this. Camera images are typically 24-bit RGB pixels, only 8
bits per color, and a simple inspection shows that is hardly resolved.

From:	GTO
Subject:	Re: Nikon D70 DSLR on microscope: Update
Date:	Thu, 30 Dec 2004 00:52:13 GMT

As Mikhail has already pointed out, one of the TIFF file format uses 8 bit
per color channel, or 24 bit per pixel. Independent of the file format, a
digital camera stores the image in an internal format that has no direct
color information stored. Depending on the way color is actually measured, a
digital camera could use a Bayer filter or three image sensors with a
splitter that separates different wavelengths accordingly. In either case,
information is stored as digitized values that have been read from analog
input. With a Bayer filter and 12-bit A/D, a digital camera would then
provide a pixel array of values from 0 to 4095. Its firmware would then
recreate color information based on intensity variations of neighboring
pixels. In this case, the color resolution across the image is less than the
spatial resolution given by the amount of active pixels in the image sensor.
If you now save this so called RAW image format to disk, it can be post
processed in much more sophisticated ways than a 24-bit TIFF file. Usually,
people save such files in 48-bit TIFF (16-bit per color channel) or a format
suitable to handle the increased amount of information. With the D70, I save
images in compressed NEF (NEF = Nikon Electronic Format). Remember, when I
save an image in compressed NEF, almost the originally obtained information
from the image sensor together with many settings, which were used when
capturing the image, are saved. It is also not too large since a 6 MPixel
NEF file is just about 5 to 6 MBytes in size.

Gregor

"Richard J Kinch" wrote in message
news:Xns95CE3D225759Fsomeconundrum@216.196.97.131...
> GTO writes:
>
>> The dynamic range of digital vs. film needs some clarification. A
>> dedicated microscopy camera with a 14 or even 16-bit A/D offers a
>> comparable dynamic range to the one of color negative film (up to 9
>> f-stops). The 12-bit A/D of most digital cameras offers at least as
>> much dynamic range as color slide film (5 to 6 f-stops).
>
> I don't follow this. Camera images are typically 24-bit RGB pixels, only 8
> bits per color, and a simple inspection shows that is hardly resolved.

From:	Richard J Kinch
Subject:	Re: Nikon D70 DSLR on microscope: Update
Date:	Thu, 30 Dec 2004 01:16:50 -0600

GTO writes:

> With a Bayer filter and 12-bit A/D, a digital camera would then
> provide a pixel array of values from 0 to 4095.

Yeah, I know they'll transmit data in 12 bits, but is the chip truly
resolving 12 bits? It seems like even 8 bits has a lot of noise.

From:	GTO
Subject:	Re: Nikon D70 DSLR on microscope: Update
Date:	Thu, 30 Dec 2004 07:42:53 GMT

Yes, I am pretty sure that the Nikon D70 provides true 12-bit imaging.

Do you mean digital noise? Digital noise comes in at least three flavors,
bias noise, read noise and thermal noise. While the first two are associated
with the camera electronics, thermal noise comes from the image sensor. Now,
digital noise is not directly related to the A/D's bit depth. You can get a
lot of noise on a 12-bit device, while enjoying less noise with a different
10-bit device.

Today, 12-bit imaging at high quality (low noise) can be obtained.
Especially the Nikon D70 is far superior to the cheaper digicams with regard
to digital noise. Have you tried the D70? It's an amazing piece of
equipment. Digital photography with affordable cameras has come a long way
over the last twelve months.

Gregor

"Richard J Kinch" wrote in message
news:Xns95CF173347504someconundrum@216.196.97.131...
> GTO writes:
>
>> With a Bayer filter and 12-bit A/D, a digital camera would then
>> provide a pixel array of values from 0 to 4095.
>
> Yeah, I know they'll transmit data in 12 bits, but is the chip truly
> resolving 12 bits? It seems like even 8 bits has a lot of noise.

From:	Richard J Kinch
Subject:	Re: Nikon D70 DSLR on microscope: Update
Date:	Sat, 01 Jan 2005 17:01:02 -0600

GTO writes:

> Do you mean digital noise? Digital noise comes in at least three
> flavors, bias noise, read noise and thermal noise. While the first two
> are associated with the camera electronics, thermal noise comes from
> the image sensor. Now, digital noise is not directly related to the
> A/D's bit depth. You can get a lot of noise on a 12-bit device, while
> enjoying less noise with a different 10-bit device.

I mean any kind of noise.

A 12-bits/color pixel is not truly resolving 12 bits if, say, the 4 least
significant bits are just noise. It is only resolving 8 bits.

> I am pretty sure that the Nikon D70 provides true 12-bit imaging.

Then I'd like to see a test image of, say, a gradient target that showed a
smooth gradient in all 12 bits.

I don't really know how today's cameras perform in this regard. I just
know that in the past, the resolution figures (both spatial and depth) have
typically been exaggerated. Also the case with scanners.

From:	GTO
Subject:	Re: Nikon D70 DSLR on microscope: Update
Date:	Sat, 01 Jan 2005 23:39:51 GMT

Try the tools from http://www.imatest.com/. The same company also wrote an
interesting PowerPoint presentation about digital versus film imaging. As
pointed out in their paper, the Shannon information capacity (a measure for
image quality) cannot easily be calculated but many features can be
experimentally determined. Although, there is no direct functional relation
between analog to digital conversion and tonal range (in f-stops), the tonal
range of a D70 covers close to six f-stops while the Coolpix 990 is limited
to a little more than four. A good example is to take images from blood
cells in brightfield. The Coolpix 990 shows a rather poor performance while
the D70 performs significantly better.

Do you know of the new FUJI S3 Pro? This new camera is announced to support
a 14-bit sampling by providing two different photo sensors in place of just
one. Or did you try cameras for astrophotography, such as the SBIG cameras
using 16-bit? With the SBIG, the dynamic range is huge and my tests of
stained white blood cells show very clear contrast differences, which are
mostly washed out with other cameras. Unfortunately, the Peltier cooled SBIG
camera forces me to reduce the brightfield illumination with a rather large
stack of grey filters. It's ideal for fluorescence microscopy but a complete
overkill for bightfield. Again, increased A/D offers a dramatically
increased tonal range.

You need to compare different cameras and draw your own conclusions based on
your experiments. A test image that got converted into a JPEG image or a
24-bit TIFF is no longer capable to show you objectively a difference. The
information by Imatest should give you enough to conduct your own and
hopefully objective measurments.

Gregor

"Richard J Kinch" wrote in message
news:Xns95D1B746EB401someconundrum@216.196.97.131...
> GTO writes:
>
>> Do you mean digital noise? Digital noise comes in at least three
>> flavors, bias noise, read noise and thermal noise. While the first two
>> are associated with the camera electronics, thermal noise comes from
>> the image sensor. Now, digital noise is not directly related to the
>> A/D's bit depth. You can get a lot of noise on a 12-bit device, while
>> enjoying less noise with a different 10-bit device.
>
> I mean any kind of noise.
>
> A 12-bits/color pixel is not truly resolving 12 bits if, say, the 4 least
> significant bits are just noise. It is only resolving 8 bits.
>
>> I am pretty sure that the Nikon D70 provides true 12-bit imaging.
>
> Then I'd like to see a test image of, say, a gradient target that showed a
> smooth gradient in all 12 bits.
>
> I don't really know how today's cameras perform in this regard. I just
> know that in the past, the resolution figures (both spatial and depth)
> have
> typically been exaggerated. Also the case with scanners.

From:	Richard J Kinch
Subject:	Re: Nikon D70 DSLR on microscope: Update
Date:	Mon, 03 Jan 2005 16:52:17 -0600

GTO writes:

> You need to compare different cameras and draw your own conclusions
> based on your experiments.

Well, yes, but I was hoping someone else had already done all that work.

From:	Gordon Couger
Subject:	Re: Nikon D70 DSLR on microscope: Update
Date:	Tue, 04 Jan 2005 04:16:36 -0600

GTO writes:
>
>
>>You need to compare different cameras and draw your own conclusions
>>based on your experiments.
>
It would be nice if we could develop a simple set test that
could be standardized so you can preform it on your stuff and I
on mine and with out any subjective evaluations demonstrated
the performance of any imaging system to the extreme limits.

I have no idea how to design it. Even finding a way to test one
element would be a great start. The performance of cameras in
low light is one that is puzzling me at the moment.

Gordon

From:	Gordon Couger
Subject:	Re: Nikon D70 DSLR on microscope: Update
Date:	Tue, 04 Jan 2005 04:36:38 -0600

GTO wrote:
> Try the tools from http://www.imatest.com/. The same company also wrote an
> interesting PowerPoint presentation about digital versus film imaging. As
> pointed out in their paper, the Shannon information capacity (a measure for
> image quality) cannot easily be calculated but many features can be
> experimentally determined. Although, there is no direct functional relation
> between analog to digital conversion and tonal range (in f-stops), the tonal
> range of a D70 covers close to six f-stops while the Coolpix 990 is limited
> to a little more than four. A good example is to take images from blood
> cells in brightfield. The Coolpix 990 shows a rather poor performance while
> the D70 performs significantly better.
>
> Do you know of the new FUJI S3 Pro? This new camera is announced to support
> a 14-bit sampling by providing two different photo sensors in place of just
> one. Or did you try cameras for astrophotography, such as the SBIG cameras
> using 16-bit? With the SBIG, the dynamic range is huge and my tests of
> stained white blood cells show very clear contrast differences, which are
> mostly washed out with other cameras. Unfortunately, the Peltier cooled SBIG
> camera forces me to reduce the brightfield illumination with a rather large
> stack of grey filters. It's ideal for fluorescence microscopy but a complete
> overkill for bightfield. Again, increased A/D offers a dramatically
> increased tonal range.
>
> You need to compare different cameras and draw your own conclusions based on
> your experiments. A test image that got converted into a JPEG image or a
> 24-bit TIFF is no longer capable to show you objectively a difference. The
> information by Imatest should give you enough to conduct your own and
> hopefully objective measurments.
>
> Gregor
>
> "Richard J Kinch" wrote in message
> news:Xns95D1B746EB401someconundrum@216.196.97.131...
>
>>GTO writes:
>>
>>
>>>Do you mean digital noise? Digital noise comes in at least three
>>>flavors, bias noise, read noise and thermal noise. While the first two
>>>are associated with the camera electronics, thermal noise comes from
>>>the image sensor. Now, digital noise is not directly related to the
>>>A/D's bit depth. You can get a lot of noise on a 12-bit device, while
>>>enjoying less noise with a different 10-bit device.
>>
>>I mean any kind of noise.
>>
>>A 12-bits/color pixel is not truly resolving 12 bits if, say, the 4 least
>>significant bits are just noise. It is only resolving 8 bits.
>>
>>
>>>I am pretty sure that the Nikon D70 provides true 12-bit imaging.
>>
>>Then I'd like to see a test image of, say, a gradient target that showed a
>>smooth gradient in all 12 bits.
>>
>>I don't really know how today's cameras perform in this regard. I just
>>know that in the past, the resolution figures (both spatial and depth)
>>have
>>typically been exaggerated. Also the case with scanners.
>
Noise can be used to your advantage if it random. If you use
soft ware to average enough images and the noes is truly random
It cancels itself out and leaves more informations about the
image that was not detectable by the sensor. it works best if
amplitude of the noise is exactly the same value of the voltage
that equals 1 bit. For example with an 8 bit a/d converter
digitizing a 1 volt signal the noise would work best if it was
exactly 1/256 or 0.00390625 volts. While hinger noise will give
even greater improvement in practice you have to average too
many images to make it worth while.

Gordon

From:	Richard J Kinch
Subject:	Re: Nikon D70 DSLR on microscope: Update
Date:	Tue, 04 Jan 2005 16:57:38 -0600

Gordon Couger writes:

> Noise can be used to your advantage if it random. If you use
> soft ware to average enough images and the noes is truly random
> It cancels itself out and leaves more informations about the
> image that was not detectable by the sensor.

Additive noise can be analyzed out by repeated sampling, yes, but if the
resolution isn't really there to start with, you're just sampling noise,
and not physical reality.

Some years ago I was really skeptical about spatial resolution claims of
digital cameras, and indeed when reviewers finally got around to actually
shooting resolution test images, it was concretely demonstrated that the
specs were "exaggerated" (false, lying). Like watts in audio equipment, or
horsepower in air compressors.

I haven't seen any discriminating tests of grayscale resolution. I would
really like to see a sample image of a gradient target that delivered a
gradient in the pixels down to the 12-bit (or whatever) resolution these
camera manufacturers are bragging about. 3.6 decimal digits of dynamic
range is quite an achievement.

From:	Mikhail Arkhipov
Subject:	Re: Nikon D70 DSLR on microscope: Update
Date:	Wed, 29 Dec 2004 11:19:47 -0800

Not quite. 24 bit is just one of the image formats. Most good cameras
internally are at least 12 bit. In many cameras you can save images in 16
bit RAW or TIFF.

Now, about dynamic range. Digital dynamic range hardly matches negative, but
easily matches slide. What you are observing as 'blown' highlights, are, in
fact, exposure meter errors, not sensor errors. Same way you can blow
highlights using slide film if you make incorrect exposure or rely on simple
camera meter. Slide film is not forgiving, negative film allows large
exposure errors.

If your camera consistently blows highlights, try underexpose by 0.5 stops
and then correct in Photoshop or another image editing application.

Thanks
Mikhail

On 12/29/04 3:00, in article Xns95CE3D225759Fsomeconundrum@216.196.97.131,
"Richard J Kinch" wrote:

> GTO writes:
>
>> The dynamic range of digital vs. film needs some clarification. A
>> dedicated microscopy camera with a 14 or even 16-bit A/D offers a
>> comparable dynamic range to the one of color negative film (up to 9
>> f-stops). The 12-bit A/D of most digital cameras offers at least as
>> much dynamic range as color slide film (5 to 6 f-stops).
>
> I don't follow this. Camera images are typically 24-bit RGB pixels, only 8
> bits per color, and a simple inspection shows that is hardly resolved.