Need help selecting digital camera

On Thu, 27 Nov 2008 06:51:19 -0800 (PST), wrote:

On Nov 25, 8:31*pm, Dave Boland wrote:
Newsgroup,

I need to get a digital camera to replace the Polorid 600, and would
appreciate any help. *Some information about the camera use to help
guide the comments:

* The camera will be used mostly for documentation of things like
scope traces, printed circuit traces, control panel pictures, and some
field test items that may be in bright sun. *

That can be difficult for many of the possible cameras. I would
not be so hot to take advantage of Black Friday and risk getting a
camera that will not be suitable for your needs.

I am particularly concerned about the scope traces. Any of the
point and shoot cameras could have problems. Scopes vary with the
scan rate and decay rates. If the shutter is too fast, and you can
expect limited or no control over the shutter speed with a point and
shoot digital, you may have unacceptable results.

You need to understand how oscilloscopes work. They are not refreshed according
to some set rate, like TVs and computer monitors screens are (I can understand
your confusion about this, you've only read photography books). The scan-rate in
an oscilloscope is user selected or waveform triggered. If you want to capture a
trace that takes 2 seconds to show its passage you'll need a camera that has a
2-second shutter speed to record it. A scan rate set at 20-KHz will take
5/100,000th of a second for each sweep of the electron gun. Any camera will
capture a composite of many of those, because the oscilloscope screen is
refreshing much faster than most any camera's fastest shutter speed.

Unless you wanted to record only 1 of the scan's passages across the scope
instead of an average of many scans. Then you'd need a CHDK compatible P&S
camera that can have a shutter speed up to 1/40,000th of a second (25KHz),
without flash. Using flash to stop something that fast that's illuminated would
destroy any chance of recording it.

The interesting part about a CHDK supported camera, is that by using the
fractional decimal method of choosing a shutter-speed, instead of the typical
preset 1/3EV values used in photography, you can dial in the exact shutter-speed
you'd need to capture one and only 1 full trace up to 1/40,000th of a second.
Provided of course that your scope display can be set bright enough so that one
scan line can provide for a usable exposure. You also have to take into account
the difference between the oscilloscope's display-tube fluorescence and
phosphorescence lag. This is wholly dependent on the type of phosphor used on
that CRT. The phosphorescence lag will be your limiting factor for accuracy.
(Here's the first google hit I got showing a chart of these phosphor refresh
delays, some are specifically designed for high-speed oscilloscopes
http://www.tubecollector.org/documents/numbers-16.htm There are better charts
out there, but this will suffice to show what is meant.)

Example: You know that your oscilloscope is scanning at 15kHz rate. In CHDK's
"Extra Photo Operations" menu you'd set it for:

Shutter Speed Enum Type: Factor
Override Shutter Speed: 6
Value Factor: 1/100,000

(reciprocal of 6/100,000 = 16,666 Hz)

This ensures that you'll capture only 1 sweep of the oscilloscope display. Or as
near-to as possible by using any camera made today.

Conclusion: If you really want to record an oscilloscope's display accurately, a
P&S camera is your only option--one that is capable of running the firmware
enhancement of CHDK

See this page for which models are supported: http://chdk.wikia.com/wiki/CHDK

For those of you that aren't aware of another problem caused by focal-plane
shutters, which is not a limitation of leaf-shutters, do a simple experiment. A
tube-type TV is nothing more than an oscilloscope running at a set 50Hz or 60Hz.
Photograph the screen of your CRT type television (the tube-type display, not
LCD or other) with a DSLR camera and then a P&S camera at 1/500 shutter speed.
In the DSLR you'll see a bent block of scan-lines in your image. The faster the
shutter speed that you use the more easily you'll see this distortion This is
caused by the agonizingly slow passage of that focal-plane shutter's slit across
the sensor. Using a P&S camera with a leaf-shutter you'll see a nice even block
of properly recorded scan-lines. This is how leaf-shutter accuracy was easily
tested for true speeds a few decades ago. Count the full TV scan-lines recorded
and there's your accurate shutter speed. (Calculated from your display's
refresh-rate in your country. 50Hz or 60Hz)




I would suggest making sure you can return the camera if it fails
to meet your needs, or ask to borrow the demo to test it out.

Good Luck


Thanks for any serious suggestions.
Dave

Dave Boland wrote:
Newsgroup,

I need to get a digital camera to replace the Polorid 600, and would
appreciate any help. Some information about the camera use to help
guide the comments:

* The camera will be used mostly for documentation of things like scope
traces, printed circuit traces, control panel pictures, and some field
test items that may be in bright sun. Light levels run from normal room
lighting to bright sun. Speed from stationary, to oscilloscope display,
to moderately fast moving (1/30s to 1/250s typically).

* Users of the camera vary between no photography experience, to a fair
amount of experience. That said, the camera should be as simple to use
as possible because I don't want people spending time tweaking settings.

* Picture size is typically 5 in. by 7 in. some are larger.

* Budget is limited and I would like to stay at $100 (U.S.) or less.

* Features that seem important a
- Easy to use is number 1, which includes controls and menus.
- Very good quality pictures (focus, exposure, color) important.
- Very reliable.
- Easy to use in the sun. I like viewfinders for this, but...
- Optical zoom of 3 to 1 or better.
- Batteries that can be obtained at 'mart's is a must.
- Easy to down-load to P.C. or printer, and quickly.
- Macro would be nice for close-ups of circuit card failures.
- Manual controls would be nice, at least for some of us.

Some cameras that I'm considering are the ones that will be on sale for
black Friday. They a
http://www.walmart.com/catalog/produ...83 2852010904

http://www.walmart.com/catalog/produ...16 2793659556

Nikon Coolpix L18 Digital Camera - $99.99 at Ritz
Olympus Stylus 760 Digital Camera - $99.99 at Ritz
Kodak EasyShare C913 9MP 2.5" LCD With Free Canon Photo Printer, $79.99
at Staples
Casio EX-Z9 8.1MP Digital Camera - $99.99 at K-Mart (Thur. only)
Kodak EasyShare MX1063 10MP Digital Camera w/ 3x Zoom - $89.00 Target

Thanks for any serious suggestions.
Dave



Thanks for all the responses. Some have been very helpful. I regret
the anger that it caused some, but that is life. To clear up one
thing, I do understand analog scopes very well. My concern was that
the readers of this forum would not. I agree, capturing a trace is
challenging. Currently I do it with my Nikon film camera, but it is a
pain to have to get the film developed because it takes time. A
digital would be good, but I also agree that it is wise to take my
time and investigate the cameras before I buy.

Hope everyone had a good Thanksgiving (U.S.).

Dave,

Dave Boland wrote:

* Features that seem important a
- Easy to use is number 1, which includes controls and menus.
- Very good quality pictures (focus, exposure, color) important.
- Very reliable.
- Easy to use in the sun. I like viewfinders for this, but...
- Optical zoom of 3 to 1 or better.
- Batteries that can be obtained at 'mart's is a must.
- Easy to down-load to P.C. or printer, and quickly.
- Macro would be nice for close-ups of circuit card failures.
- Manual controls would be nice, at least for some of us.

Get the Canon A590IS. It's $102.

"http://www.newegg.com/Product/Product.aspx?Item=N82E16830120256&CMP=AFC-C8Junction"

Use "CAMERA118" coupon for $8 off.

It has everything you need. If you need more manual control you can use
CHDK firmware on it.

On Fri, 28 Nov 2008 10:41:57 -0800, SMS wrote:

Dave Boland wrote:

* Features that seem important a
- Easy to use is number 1, which includes controls and menus.
- Very good quality pictures (focus, exposure, color) important.
- Very reliable.
- Easy to use in the sun. I like viewfinders for this, but...
- Optical zoom of 3 to 1 or better.
- Batteries that can be obtained at 'mart's is a must.
- Easy to down-load to P.C. or printer, and quickly.
- Macro would be nice for close-ups of circuit card failures.
- Manual controls would be nice, at least for some of us.

Get the Canon A590IS. It's $102.

"http://www.newegg.com/Product/Product.aspx?Item=N82E16830120256&CMP=AFC-C8Junction"

Use "CAMERA118" coupon for $8 off.

It has everything you need. If you need more manual control you can use
CHDK firmware on it.

Oh goody, our resident google-photographer is back. He'll do all our googling
and look up things in manuals for us. It's as close as he ever personally gets
to anything photography related. Let's let him live out his phantasy while being
our internet coolie, gofer, and grunt.

Yes, even virtual-photographer trolls can have their uses.

FETCH, BOY!

Good boy, atta boy. Now go lay down in your cage until we need you again.

Dave Bernstein wrote:
On Fri, 28 Nov 2008 10:41:57 -0800, SMS wrote:


Dave Boland wrote:


* Features that seem important a
- Easy to use is number 1, which includes controls and menus.
- Very good quality pictures (focus, exposure, color) important.
- Very reliable.
- Easy to use in the sun. I like viewfinders for this, but...
- Optical zoom of 3 to 1 or better.
- Batteries that can be obtained at 'mart's is a must.
- Easy to down-load to P.C. or printer, and quickly.
- Macro would be nice for close-ups of circuit card failures.
- Manual controls would be nice, at least for some of us.

Get the Canon A590IS. It's $102.

"http://www.newegg.com/Product/Product.aspx?Item=N82E16830120256&CMP=AFC-C8Junction"

Use "CAMERA118" coupon for $8 off.

It has everything you need. If you need more manual control you can use
CHDK firmware on it.


Oh goody, our resident google-photographer is back. He'll do all our googling
and look up things in manuals for us. It's as close as he ever personally gets
to anything photography related. Let's let him live out his phantasy while being
our internet coolie, gofer, and grunt.

Yes, even virtual-photographer trolls can have their uses.

FETCH, BOY!

Good boy, atta boy. Now go lay down in your cage until we need you again.


I don't see how this is helpful. If you have a better idea, then
let's hear it. Otherwise, it may be time to refocus you energy.

Dave (OP)

On Thu, 27 Nov 2008 16:30:38 -0600, SmarterGuy wrote:

For those of you that aren't aware of another problem caused by focal-plane
shutters, which is not a limitation of leaf-shutters, do a simple experiment. A
tube-type TV is nothing more than an oscilloscope running at a set 50Hz or 60Hz.
Photograph the screen of your CRT type television (the tube-type display, not
LCD or other) with a DSLR camera and then a P&S camera at 1/500 shutter speed.
In the DSLR you'll see a bent block of scan-lines in your image. The faster the
shutter speed that you use the more easily you'll see this distortion This is
caused by the agonizingly slow passage of that focal-plane shutter's slit across
the sensor. Using a P&S camera with a leaf-shutter you'll see a nice even block
of properly recorded scan-lines. This is how leaf-shutter accuracy was easily
tested for true speeds a few decades ago. Count the full TV scan-lines recorded
and there's your accurate shutter speed. (Calculated from your display's
refresh-rate in your country. 50Hz or 60Hz)

Minor Correction/Clarification:

If the slit of the focal-plane shutter is moving parallel to the scan lines on
the TV (or CRT computer monitor) display then you may not first see the
bent-block distortion caused by the typical horizontally moving focal-plane
shutters of the past. But it also won't reveal the true shutter speed either by
trying to count the scan lines. This is because if the shutter's slit is moving
parallel with the forming scan-lines then they will be either compressed or
expanded vertically. (Just as a diver diving into a pool of water will be
compressed or stretched a bit, distorted, by being photographed with a
focal-plane shutter camera.) In many modern cameras the focal-plane shutter was
changed from a horizontal motion to a vertical motion to increase apparent
speed. The narrower distance of the image-frame being a shorter distance to
traverse, doing so "faster" at the same speeds as all of last-century's shutter
curtains.

If you don't notice this distorted curved block of TV/CRT scan lines when
photographed with your dSLR at shutter speeds faster than x-sync, just tilt the
camera to portrait mode and shoot again. There will be your direct evidence of
focal-plane shutter distortion. In some focal-plane shutter designs faster
speeds were obtained by reorienting the shutter's slit from being parallel to
one side of the frame to a more diagonal orientation. Then this distortion will
show up in either orientation of the camera, landscape or portrait. For example,
see this $43,000 Hasselblad M8 camera's focal-plane shutter:
http://www.farines-photo.com/wp/wp-c...shutter_m8.png

(I guess it's true, you do get what you pay for. Even more chance of distortions
by paying higher prices. The focal-plane shutter distortions, now happening in
both orientations of the camera caused by the Hasselblad's diagonal shutter,
being just one of the many problems with the M8 camera. The M8's problems are
voluminous. Most images no better than a $70 discount-store bubble-pack camera
that hangs from a display hook. Now don't forget, "You get what you pay for!"
Keep saying that. It might come true one day. Then you'll be able to finally
justify why you spend so much money.)

This distortion doesn't just happen at speeds above x-sync either. If you study
the TV/CRT scan-line image carefully you will notice that you get distorted
ghosted (lesser exposed) scan-lines from the partial exposure as the individual
curtains slowly open and close too. Just because the full frame is fully open at
one point doesn't mean the full frame is completely exposed during the total
exposure at all times. The focal-plane shutter design, no matter how it is
implemented, is fraught with problems. This being just one of many.

Leaf-shutter cameras/lenses have none of these problems.

Dave Boland wrote:

Thanks for all the responses. Some have been very helpful. I regret
the anger that it caused some, but that is life. To clear up one thing,
I do understand analog scopes very well. My concern was that the
readers of this forum would not. I agree, capturing a trace is
challenging. Currently I do it with my Nikon film camera, but it is a
pain to have to get the film developed because it takes time. A digital
would be good, but I also agree that it is wise to take my time and
investigate the cameras before I buy.

I remember in high school electronics class we had a Polaroid Scope
Camera. It was a really good deal at the time compared to the ones the
scope companies sold.

I think you'll just need to fashion some sort of a hood for the camera
and play with the manual settings, and perhaps use CHDK.

Dave Boland wrote:

I don't see how this is helpful. If you have a better idea, then let's
hear it. Otherwise, it may be time to refocus you energy.

Dave (OP)

LOL, since when has our favorite troll ever been helpful? Especially
since unlike him, I actually have used digital cameras for scope traces
(though thankfully now I use digital storage scopes!).

Anyway, there's some other reasons why something like the A590 would be
suitable. There is a way to attach extension lenses and tubes, and such
a device would be very helpful in fashioning a hood that fits over the
scope tube and onto the camera. And as I stated before, if you need more
manual control, at least on the Canon models there's a way to get it.
Yeah, a lot of the CHDK stuff is geeky, but some of it is quite useful,
especially when you're doing out of the ordinary stuff like this.

Look at
"http://www.truetex.com/tektronix_xg_polaroid_oscilloscope_hood_adapter.pd f"
for some ideas, and remember it's much easier if the digital camera is
designed for lens tubes and conversion lenses.

SMS wrote:

Dave Boland wrote:

Thanks for all the responses. Some have been very helpful. I regret
the anger that it caused some, but that is life. To clear up one
thing, I do understand analog scopes very well. My concern was that
the readers of this forum would not. I agree, capturing a trace is
challenging. Currently I do it with my Nikon film camera, but it is a
pain to have to get the film developed because it takes time. A
digital would be good, but I also agree that it is wise to take my
time and investigate the cameras before I buy.


I remember in high school electronics class we had a Polaroid Scope
Camera. It was a really good deal at the time compared to the ones the
scope companies sold.

I think you'll just need to fashion some sort of a hood for the camera
and play with the manual settings, and perhaps use CHDK.

I've used those devices on the older Tek. scopes. They work well.
The hood provided the correct focal length and kept out extraneous
light. The hood had to fit the bezel of the scope display. I'm not
worried about ambient light or focal length because I can controll
both of them.

Dave,

On Fri, 28 Nov 2008 18:50:30 -0600, Arnie_R_Ungers
wrote:


If the slit of the focal-plane shutter is moving parallel to the scan lines on
the TV (or CRT computer monitor) display then you may not first see the
bent-block distortion caused by the typical horizontally moving focal-plane
shutters of the past. But it also won't reveal the true shutter speed either by
trying to count the scan lines. This is because if the shutter's slit is moving
parallel with the forming scan-lines then they will be either compressed or
expanded vertically. (Just as a diver diving into a pool of water will be
compressed or stretched a bit, distorted, by being photographed with a
focal-plane shutter camera.) In many modern cameras the focal-plane shutter was
changed from a horizontal motion to a vertical motion to increase apparent
speed. The narrower distance of the image-frame being a shorter distance to
traverse, doing so "faster" at the same speeds as all of last-century's shutter
curtains.

I suppose you could test the true speed of a focal-plane shutter with this
method. Just determine your shutter's direction of travel. If top to bottom then
orient that to the TV/CRT display, top to bottom. Your motive is to align the
shutter's slit to be parallel with the scan-lines of the display. Take a
picture. Now flip the camera upside down to show the other extreme of this
compression and expansion distortion created by all focal-plane shutters. Take
the average number of scan-lines between both images and that could be used to
test the accuracy of your shutter. If the shutter's direction of travel is
horizontal then hold the camera in portrait mode. One shot one way, the next
shot with the camera turned 180-degrees.

If you use a slanted-slit focal-plane shutter as in that who-on-earth-would-be-
stupid-enough-to-buy-that-thing Hasselblad, then you'll have to determine the
angle of that moving slit and make it parallel with the scan-lines on your
TV/CRT display. Again, taking one of each, the second shot with camera turned
180-degrees from the first one.