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Author Topic: Photographing an O'scope screen  (Read 3791 times)
K8AXW
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Posts: 3739




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« on: March 01, 2011, 09:16:59 AM »

Greetings all:

I have tried photographing waveforms on my oscilloscope with my new digital camera without acceptable results.

Can anyone tell me how they do this without recording the reflections on the screen along with the waveform?

K8AXW
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WB2EOD
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Posts: 217




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« Reply #1 on: March 01, 2011, 10:06:52 AM »

I don't know your setup.  Forgive me if I am covering anything you have already tried.
Strong room light and flash are your worst enemies.  Both will obliterate the scope display with reflections.

Disable the camera's flash, you will be shooting with existing light.

Turn up the scope intensity and the scale illumination (if equipped). 

If you have interchangeable lenses, choose one that can shoot close to the subject, you will be shooting as close as you can get while framing the entire CRT display

Turn off or reduce the room lights.  You will be using slow shutter (maybe a second or more) so you will want to mount the camera on a tripod and use a remote release (used to be called a cable release). 

From there you will have to experiment on exposure time, and maybe some additional light.  With the immediate nature of digital photography you should get it fairly quickly

You are lucky, the last time I had to this was before the digital age. 
I ended up shooting (and processing) 24 pictures before I got it right. 

Hope this helps
73
WB2EOD

 
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KC8IUR
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Posts: 156




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« Reply #2 on: March 01, 2011, 10:26:23 AM »

I haven't ever attempted a photograph of a display before, but I would probably put on a circular polarizing filter, aim my flash backwards, up over my head and bounce it indirectly onto the screen with white paperboard. You will need a long exposure to capture the whole image, so you will probably need some sort of artificial illumination.

I have an old D-SLR, so I would take a bunch of shots, tweaking the light, polarization and exposure until I achieved the desired effect. Digital is free that way.
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WX7G
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« Reply #3 on: March 01, 2011, 12:53:38 PM »

It works ok if the flash is shut OFF.
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K2OWK
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Posts: 1054




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« Reply #4 on: March 01, 2011, 01:51:47 PM »

Hello K8AXW, Back in the old days they had a scope camera made by Graflex with a Polaroid back. It used Polaroid film. This set used a square tube that mounted to the O-scope display bezel. The reason I gave this information is to tell you how to make a scope camera. A stiff cardboard folded around the scope bezel to form a square tube, On the front of the tube mount a cardboard piece to cover the opening and cut a hole to just fit your camera lens. Paint the inside of the tube with flat black spray paint. To take semiprofessional pictures of your scope display focus the camera on the scope screen with the trace bright and the grid light clear and visible in the cameras viewfinder. Use manual focus. You made need a closeup lens if your camera will not focus down enough to sharpen the scopes display. I left out the length of the tube, because you will need to check your cameras focal distanced to the screen to determine its length.

I know it sounds complicated, but it is really very easy to construct, and once made will always be available for easy use.

I hope this helps.

Regards,
Barry K2OWK
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KE3WD
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« Reply #5 on: March 01, 2011, 02:34:18 PM »

A black cardboard lightshield shaped like a hood to go from just the scope screen to the lens of the camera (kind of like a squarish funnel shape) will block all glare.  The intensity of the scope trace is enough light when the shutter speed, etc. are set for it. 

Many scope manufacturers sold hoods such as this, as well as hoods that had polaroid camera backs attached. 

Haven't used one in years, today I use digital scopes with screen capture for documentation, but the old camera method as described above worked then and can work as well now.


73
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K8AXW
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« Reply #6 on: March 01, 2011, 04:04:49 PM »

OK!  Now we're cookin with gas!  My fairly inexpensive digital camera has no interchangeable lens.  It is autofocus.  It also has two macro settings.

I've tried taking the pictures with light, without light, both macro settings, zoom from 3 or 4 feet....all have one problem or another.  It's either reflections on the scope screen or bloom caused by the scope trace in a dark room.  I've also cut the intensity of the trace and when I do that the square wave looks like dashes in the camera. 

The black "hood" description sounds like an inexpensive and feasible way to go.  I was thinking of an anti-glare screen of some sort. 

What also complicated this to a great degree is that my scope does not have  graticule illumination. 

Thank you gentlemen for your suggestions.  If anyone else cares to comment, please do.  This is a whole new game for me because my scope is fairly new and my digital camera is new.  I'm still learning to operate both.
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KE4DRN
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« Reply #7 on: March 01, 2011, 04:41:12 PM »

hi,

you can use a mailing tube or small carton for the hood,
similar to this (without the camera).

http://www.eqrentals.com/sale/details/HES3196.html

use a printed sheet to place in front of the screen so the
camera can focus and lock onto the image, graph paper is good.

try setting the camera for sports or action photos,
or try to take a short movie and then grab a screen image
once you have the movie on the pc.

Avoid the macro setting, you can always zoom in and
crop the photos later before printing.

73 james
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W5FYI
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« Reply #8 on: March 01, 2011, 07:11:13 PM »

I hate to say it, but some of the advice you're getting is hardly worth what you're paying.  You don't want to use flash, or any room illumination--the flying dot is self-illuminating and the graticule should have the capability of being illuminated, but I understand you can't do that.  Nor should you use sports or action settings, unless you want to stop the dot in mid trace. While most scopes have a persistence-of-image, a long exposure will give the trace a more even exposure.

It would be best if your camera could have settings for focus, aperture and shutter speeds so you could get reproducible results; a totally-automatic autofocus camera will probably never work very well. A camera hood, like the old Polaroid scope hoods, will both hold the camera steady and at correct focus, and keep out ambient light. Digital cameras with a viewing screen on back are much better that the old film cameras, because generally what you see is what you'll get. GL
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K8AXW
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« Reply #9 on: March 01, 2011, 08:11:47 PM »

OK.... I've been thinking about this camera hood some, since I haven't had time to actually build one yet.... so I'm wondering what the difference is between shooting with a camera hood and a darkened room?

When I shoot in a darkened room the trace 'blooms' and I get a color shift from blue to green.  I've reduced the trace intensity which helps tremendously but without at least part of the scope the pictures lose a great deal of meaning.

To explain further, a picture taken in the dark of the scope screen is simply a dark block with horizontal illuminated bars (square wave).

I'd really like to have closeup photographs of the scope screen with ambient light, no reflection from the screen.  I hate to throw crap into the game people.  I have found it somewhat daunting trying to explain my problem.

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KE3WD
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« Reply #10 on: March 02, 2011, 05:19:46 AM »

Without an illuminated graticule, the hood method is not likely to work all that well. 

Blackened room would likely yield the same bad result with more to consider, such as maintaining constant focal plane (distance), etc. - and you would still not likely be able to show the graticule much if at all without illumination. 

I once published results years ago by resorting to making drawings of my scope screen, all depends on what you are after though, and how many screenshots you need. 

Might be cheaper to pick up a used scope with lighted graticule...


73
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K8AXW
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Posts: 3739




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« Reply #11 on: March 02, 2011, 07:27:58 AM »

KE3WD:

I'm inclined to agree with you.  After some thought, I can see no difference in a darkened room than a hood.  I suspect the hood would be used in an area where it would be impractical to shut off all the lights.

Changing scopes isn't an option.  I just bought this one about a year ago and feel quite fortunate to have been able to get it considering the fixed income, etc.  The inability to take quality photos of the screen is a distant second place to the benefits of my new scope.

If someone doesn't come up with a viable solution to this problem I'll just have to settle for inferior photos and live with it.

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KE4DRN
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« Reply #12 on: March 02, 2011, 03:45:42 PM »

hi,

is there a 'fireworks' setting on your digital camera?

how about using a stock photo from the web
or perhaps another on this group can get a photo
to you via email?

another way to do it would be to use a film camera,
you would have more control of exposure and focus,
have the film processed and copied to cd.

73 james
« Last Edit: March 02, 2011, 04:00:49 PM by KE4DRN » Logged
K8AXW
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« Reply #13 on: March 02, 2011, 09:17:59 PM »

I do have a "fireworks" setting-

I also have shutter priority, aperture priority, and can set either manually.

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N7NBB
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« Reply #14 on: March 03, 2011, 07:34:52 AM »

I may be missing the mark here, and I fully appreciate FINALLY getting an O-Scope, fixed income, etc. (I'm kind of on an very limited budget myself and had to wait a good long time to get an o-scope)  Having said that, have you considered just using a Computer based O-scope, (software based) then just grabbing a screen shot of the result ??  Although I still can't get beyond the "physicality" of that piece of equipment sitting on my bench, I'm slowly coming around to using a computer based scope too in some applications.  It seems you've tried lots of different things all with limited or unsatisfactory results, so I thought perhaps a screen grab of a computer based scope might just give you the results you need.  I have good results photographing my (REAL) scope with a slow shutter speed and not too high of an ISO setting (old term: slow ASA). But this is photographing a CONVENTIONAL CRT with a green phosper, not an LCD display.  Or like one other poster suggested, if you are just looking for generic scope traces, and not your own personal equipment, search the web (google images or similar) there's tons of images there for just about any waveform you need.  GOOD LUCK ! hope you find a solution.
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