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eHam Forums => Misc => Topic started by: K8AXW on March 01, 2011, 09:16:59 AM



Title: Photographing an O'scope screen
Post by: K8AXW 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


Title: RE: Photographing an O'scope screen
Post by: WB2EOD 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

 


Title: RE: Photographing an O'scope screen
Post by: KC8IUR 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.


Title: RE: Photographing an O'scope screen
Post by: KH6AQ on March 01, 2011, 12:53:38 PM
It works ok if the flash is shut OFF.


Title: RE: Photographing an O'scope screen
Post by: K2OWK 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


Title: RE: Photographing an O'scope screen
Post by: KE3WD 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


Title: RE: Photographing an O'scope screen
Post by: K8AXW 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.


Title: RE: Photographing an O'scope screen
Post by: KE4DRN 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


Title: RE: Photographing an O'scope screen
Post by: W5FYI 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


Title: RE: Photographing an O'scope screen
Post by: K8AXW 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.



Title: RE: Photographing an O'scope screen
Post by: KE3WD 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


Title: RE: Photographing an O'scope screen
Post by: K8AXW 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.



Title: RE: Photographing an O'scope screen
Post by: KE4DRN 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


Title: RE: Photographing an O'scope screen
Post by: K8AXW 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.



Title: RE: Photographing an O'scope screen
Post by: N7NBB 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.


Title: RE: Photographing an O'scope screen
Post by: W8JX on March 03, 2011, 10:02:37 AM
This is really pretty simple as to a solution. You have to be able to put camera is manual mode for shutter speed and set it to 1/30th of a second or so. You will also have to control exposure (aperture) for correct exposure. If you can get  auto to work here you are lucky. The human eye has "persistence" so that you see things that the quick eye of a camera will not record. (example with old analog TV when you take a picture it is usually garbled some unless you us a slow shutter speed.) Try this, if you can set ISO to 400 or 800 and shutter to 1/30 and play with aperture until you get a good picture. You might even have to go slower to 1/15th of a second.


Title: RE: Photographing an O'scope screen
Post by: K8AXW on March 03, 2011, 11:20:48 AM
All:

I think I am beginning to get a handle on this problem.  I've taken various suggestions presented here, analyzed them and came up with this possible solution.

I obtained a large cardboard box, painted the inside flat black.  I then cut a 5"H X 6"W hole in one end to accommodate the scope screen.

I then cut a round hole in the opposite end to accommodate the camera lens.  I attached the box to a short tripod with duct tape and tilted the box down and moved it in towards the scope.  I found it was necessary to remove the tubes from the overhead fluorescent lights to prevent light from entering the large hole in the box.

I left a 2" gap between the box and the scope so that when I took the shot I had part of the scope as well as the screen.  This gave meaning to the pictures.  In other words, I didn't have just a black square with illuminated 'dashes' as with a square wave.

Since the box was so large, it was necessary to use the zoom feature to get a full sized picture of the screen.  I left the camera on AUTO.  The results were encouraging. 

The pictures have the scope trace without reflections.  The trace was fairly sharp and leaving part of the scope in the picture gave the pictures meaning.

My next step is to find a more suitable box somewhat like the scope hood that KE4DRN sent a photo of. This will make the setup more manageable.

I think the key to this is leaving a gap between the box/hood and the scope to leave some light reach the scope face.



Title: RE: Photographing an O'scope screen
Post by: AC5UP on March 13, 2011, 08:06:35 PM
This is actually very simple once you learn how to control the lighting and exposure balance...

Adjust the scope brightness for a normal display. No bloom or flare in the bright portions but bright enough to show detail in all portions of the trace. Position the camera on a tripod (or Jerry rig) such that it's parallel and square to the face of the CRT. Turn off the flash and darken the room as needed to eliminate stray reflections on the graticule. A dark cloth draped above and around the 'scope and camera can act as a light shroud if necessary.

Check the user guide for your camera and choose a program or manual setting that gives you a slow shutter speed at an ASA equivalent of 50 or 100. The goal here is for the exposure to be long enough to cover several trace refreshes on the CRT at a sensitivity low enough that the camera doesn't try to lift the dark areas on the CRT above black / dark grey. Use the self timer feature so you won't jiggle the camera. 1/15 of a second exposure should give even brightness from left to right. If not, try a slower shutter speed.

Finally... Shoot a bit wider than what you need and crop the image with a photo editor like GIMP. You can also tweak the contrast and color balance so that if you didn't get it exactly right in the camera you can dial it in on the computer.


Title: RE: Photographing an O'scope screen
Post by: K8AXW on March 14, 2011, 09:39:10 PM
AC5UP:  Thank you for your response.  However, I have to disagree with you about it being "easy."  Your long paragraph that follows this "easy" statement points this out exactly.

So far I've found that it's beneficial to show part of the scope screen bezel to give the photo more meaning.  And therein lies part of the problem.  Once you back away from the scope to show the bezel then reflections on the scope screen start to show.

What I mean by "meaning" in the above statement is this.  If you turn off the room lights, get in close to the screen with a black cloth hood or whatever.... adjust the camera parameters so that you don't have "bloom" and you are photographing a square wave, all you will see in the photograph is a black background with two or more horizontal dashes.  If the scope has an illuminated graticule then this pretty well eliminates the problem but my scope doesn't have this feature.

I am still checking and reading any posts here about this problem.  Thank you one and all.  Please continue to "bring 'em on!"


Title: RE: Photographing an O'scope screen
Post by: W7SMJ on March 14, 2011, 10:52:52 PM
I have never tried this, but it would seem to me if you're using a tripod at a fixed distance you could take a picture of the scope in bright flood light to capture the graticule.  You then take your picture of the waveform in no light conditions.  Then take these two pictures and stack them so you have the graticle and waveform.  Since your tripod is fixed the overlay should be relatively easy to do.

I'm intriuged and might try this tomorrow night...

73,
Scott


Title: RE: Photographing an O'scope screen
Post by: K8AXW on March 15, 2011, 08:28:28 AM
SMJ:  Interesting thought.... but think you have seriously complicated an already somewhat complicated problem.  Using a digital camera, how do you "stack" pictures?  OK, you print them out and then "stack" them....... "overlay"?


Title: RE: Photographing an O'scope screen
Post by: W7SMJ on March 15, 2011, 09:18:05 AM
SMJ:  Interesting thought.... but think you have seriously complicated an already somewhat complicated problem.  Using a digital camera, how do you "stack" pictures?  OK, you print them out and then "stack" them....... "overlay"?

Not complicated at all.  I have seen "stack" and "overlay" used interchangeably with regard to digital images, although maybe they're different...  Anyway, there are several image packages that are easy to do this with.  I would suggest paint.net, it's free and not overly complicated.  I think it was developed by some MIT students...

If you use paint.net, paste one image in it (scope trace), add a layer, paste the graticle image on top of it, then adjust the opacity of the graticle image.  Done!

Works pretty slick and not complicated at all...

73,
Scott


Title: RE: Photographing an O'scope screen
Post by: KG4RUL on March 15, 2011, 05:44:50 PM
Many years ago I was using an oscilloscope to photograph the output waveform of electric fence chargers under development.  I was using a Tektronics scope with their camera mount and a polaroid back.  With the graticle not illuminated, I would open the shutter and use a single, triggered sweep to make the exposure then close the shutter.  I would then turn on the graticle and do a normal exposure using the shutter release.

One day I was working with the first pack of a fresh batch of polaroid high speed, panchromatic film.  I noticed that I was getting the graticle but NOT the trace!  I confirmed that the sweep was appearing by using the view port to observe it.  Not being able to figure out what was going wrong, I removed the partially used pack and put in into a normal camera. 

Shots taken of various scenes looked strange and an outside shot showed the grass in a strange way.  I then took a shot of a color wheel and discovered that the film appeared to have no sensitivity to green, the color of the scope trace.

So, I called the polaroid folks who put me into contact with their QC lab.  They made a quick check of other film packs from that same run and discovered that what I had observed was in fact true!  That resulted in a large recall of film packs.


Title: RE: Photographing an O'scope screen
Post by: W7SMJ on March 15, 2011, 09:16:08 PM
This actually wasn't too hard at all.  I have a five year old relatively inexpensive Canon A540 camera and it worked great with a tripod...

Here's my first image, just a picture of my scope in normal light:
http://www.flickr.com/photos/60621738@N05/5531263854/

That seemed to look OK and probably would work as-is...


Here's a picture of the trace I took dimmed down in low room lighting:
http://www.flickr.com/photos/60621738@N05/5530678723/

Here's a picture of the scope turned off in bright light:
http://www.flickr.com/photos/60621738@N05/5531264296/

I then copied the images into paint.net and then edited using the rectangle select tool to get only the screen of the dim trace and the scope turned off.  Using layering and adjusting the opacity I ended up with this:
http://www.flickr.com/photos/60621738@N05/5531263940/

I think it came out OK, although the trace looks slightly out of phase.  This was because I cropped both pictures before doing the overlay and i was slightly off in the dim trace pic.  As you can see it's hard to tell in the picture where the screen starts.  This could have been avoided by doing the crop AFTER the overlay.

Anyway, it really wasn't hard to do and really didn't take more than 5 minutes.  Give it a try!

73,
Scott


Title: RE: Photographing an O'scope screen
Post by: K8AXW on March 15, 2011, 09:31:08 PM
SMJ:  Frankly, I though you was blowing smoke up my $ss but after looking at your results, I'm impressed!  This process is definitely worth a try.  I've never used paint.net..... or anything similar.  While I use and I'm able to upgrade, modify, repair computers, when it comes to software I'm as dumb as a coal bucket.

But, will check this out.  Many thanks for another path to investigate.