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Posted: 10/22/2014 6:02:59 PM EDT
After staring through the camera and eyepiece I adjusted my camera to mimic my eye, and then took photos of a Mx-10130C and Mx-10130D tube.
Anyone able to give any useable values by looking at these photos? Resolution or Gain .etc Canon T2I 50mm Lens F1.4 1/25 at 400iso for High Mode 1/3rd sec at 800iso for Low Mode Mx10130D   Mx10130C   Mx10130A   |
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Posted: 10/22/2014 6:13:06 PM EDT
[#1]
Nobody can do this without a Hoffman tester. I think CJ can do resolution but anything else is just speculation. The D tube is obviously the better one. Pretty much all I can tell you.
C tubes are regular filmed and not gated. D tubes are thin film and can be gated or not. I have seen both . |
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Posted: 10/22/2014 6:18:51 PM EDT
[#2]
Quote HistoryQuoted: Nobody can do this without a Hoffman tester. I think CJ can do resolution but anything else is just speculation. The D tube is obviously the better one. Pretty much all I can tell you. I was thinking if you had a tube with a known value, you could do the following. If you can make out X group/element number in High mode you resolution is at least Y If you can make out X group/element number in low mode your gain is at least Y. |
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Posted: 10/22/2014 6:23:10 PM EDT
[#3]
Quote HistoryQuoted:
I was thinking if you had a tube with a known value, you could do the following. If you can make out X group/element number in High mode you resolution is at least Y If you can make out X group/element number in low mode your gain is at least Y. Quote HistoryQuoted:
Quoted:
Nobody can do this without a Hoffman tester. I think CJ can do resolution but anything else is just speculation. The D tube is obviously the better one. Pretty much all I can tell you. I was thinking if you had a tube with a known value, you could do the following. If you can make out X group/element number in High mode you resolution is at least Y If you can make out X group/element number in low mode your gain is at least Y. If I had the tubes in hand I could test them against known tubes I have. I can't do that from a picture though. I am pretty good at estimating tubes. I use some of the same military testers you have as you can see from my avatar. I don't have 10K for a Hoffman tester but one day that sucker will be mine !! CJ7Hawk is the best one to chime in here and hopefully he can tell you more. I told you all I can. 
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Posted: 10/22/2014 6:26:39 PM EDT
[#4]
For resolution to some extent that would be true but in order to determine gain you would need to control the ambient light. The best way is to have several monoculars with spec sheets and therefore known performance to compare it to. Test under extremes.. Almost no light and very high light conditions will tell you the most about your tube.
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Posted: 10/22/2014 6:30:27 PM EDT
[#5]
Quote HistoryQuoted: If I had the tubes in hand I could test them against known tubes I have. I can't do that from a picture though. I am pretty good at estimating tubes. I use some of the same military testers you have as you can see from my avatar. I don't have 10K for a Hoffman tester but one day that sucker will be mine !! Quote HistoryQuoted: Quoted: Quoted: Nobody can do this without a Hoffman tester. I think CJ can do resolution but anything else is just speculation. The D tube is obviously the better one. Pretty much all I can tell you. I was thinking if you had a tube with a known value, you could do the following. If you can make out X group/element number in High mode you resolution is at least Y If you can make out X group/element number in low mode your gain is at least Y. If I had the tubes in hand I could test them against known tubes I have. I can't do that from a picture though. I am pretty good at estimating tubes. I use some of the same military testers you have as you can see from my avatar. I don't have 10K for a Hoffman tester but one day that sucker will be mine !! |
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Posted: 10/22/2014 6:36:54 PM EDT
[#6]
Halo is easy to determine and resolution should be around 64 for both tubes. All I can really tell you without the tubes in hand. The C tube may be a little less resolution but it will be minor. The D tube has much more gain and a better S/N spec.
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Posted: 10/24/2014 6:37:09 AM EDT
[#7]
You need a fairly details image to read details off the tube - I think the best i've ever read ( due to lens losses ) from a 64 lp/mm PVS-14 was about 52 lp/mm. - That puts it into context. But you must use your eyes, and you must use a magnifying lens - I think I added a 10x magnifier to the tube from memory... If you want to use photo's you can't quite use a picture - however you can get a good idea from them - Just zoom right in and get things as focussed as you can - on this area -  As for which LP's mean which resolution, it's here - http://en.wikipedia.org/wiki/1951_USAF_resolution_test_chart The columns down the left is Group 2, and the column down the right is Group 3 ( though element 1 of Group 2 is down the bottom )- Group 2 element 1 is 2 lp/mm and Group 3 is 4 lp/mm. You need to get to Group 6 element 1 to get the 64 lp/mm and as you can see, it's nearly invisible, let alone possible to see individual lines in the photo - Regards David
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Posted: 10/24/2014 8:35:24 AM EDT
[#8]
Quote HistoryQuoted:
I was thinking if you had a tube with a known value, you could do the following. If you can make out X group/element number in High mode you resolution is at least Y If you can make out X group/element number in low mode your gain is at least Y. Quote HistoryQuoted:
Quoted:
Nobody can do this without a Hoffman tester. I think CJ can do resolution but anything else is just speculation. The D tube is obviously the better one. Pretty much all I can tell you. I was thinking if you had a tube with a known value, you could do the following. If you can make out X group/element number in High mode you resolution is at least Y If you can make out X group/element number in low mode your gain is at least Y. Assuming its a linear response. Which I doubt. |
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Posted: 10/24/2014 10:41:44 AM EDT
[#9]
some of the hand held testers do not use the same 1951 specs even though they look similar , they are designed to be used with a chart that lets tubes (when fitted in devices) pass or be rejected depending on the smallest lines seen , these are useful to check resolution when - like others have said - you have other tubes with datasheets to compare or to "calibrate " your tester - i have a couple of different hand held units and they each resolve different amounts (to different numbers)with the same unit.
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Posted: 10/24/2014 11:49:58 AM EDT
[#10]
Quote HistoryQuoted: Assuming its a linear response. Which I doubt. Quote HistoryQuoted: Quoted: Quoted: Nobody can do this without a Hoffman tester. I think CJ can do resolution but anything else is just speculation. The D tube is obviously the better one. Pretty much all I can tell you. I was thinking if you had a tube with a known value, you could do the following. If you can make out X group/element number in High mode you resolution is at least Y If you can make out X group/element number in low mode your gain is at least Y. Assuming its a linear response. Which I doubt. Assuming what is a linear response? Gain is fairly linear within limits at lower light levels - especially when averaged out. Anyway I wrote up the settings on a tester here: http://www.ar15.com/archive/topic.html?b=6&f=18&t=420880 MTF is usually tested at no more than about 8mLux, and I think the Gen3 high setting is around 3x that, but it's probably still suitable for an estimage - You could always add a 30% ND filter if you wanted to make it fairly accurate on Gen3 High setting. Gain isn't so easily measured, but is possible, knowing the light levels of the tester - but you'd need to build your own meter... Not so easy. But, if you have two tubes with similar high level resolution, then it's reasonable to assume that the difference between them in gain is related to the low-light resolution difference. It may not be linear, but I expect it would be close enough to approximate the difference in gain - As Dino said, these aren't hoffman testers and no one should expect to get seriously accurate information out of them - however you can get a lot from them just based on the physics of how they work if you know what you're looking for - And if you're comparing tubes for performance, they are critical tubes as they provide a constant source for comparison. Regards David
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Posted: 10/24/2014 5:18:29 PM EDT
[#11]
Thanks CJ
What do you consider to be resolved? Seeing which way the lines go? I used a magnifier and my eye, and also took a photo at 360mm both gave me the same results. The arrow points to the element I could see correct line orientation. I'm guessing this is group number 5? Which would put the resolution at only 32lp/mm? according to the wiki chart http://en.wikipedia.org/wiki/1951_USAF_resolution_test_chart Unless there is some kind of deviation in the group numbers from that page and my test unit.  |
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Posted: 10/24/2014 10:42:59 PM EDT
[#12]
Quote HistoryQuoted: Thanks CJ What do you consider to be resolved? Seeing which way the lines go? I used a magnifier and my eye, and also took a photo at 360mm both gave me the same results. The arrow points to the element I could see correct line orientation. I'm guessing this is group number 5? Which would put the resolution at only 32lp/mm? according to the wiki chart http://en.wikipedia.org/wiki/1951_USAF_resolution_test_chart Unless there is some kind of deviation in the group numbers from that page and my test unit. http://www.ar15.com/media/viewFile.html?i=69670 Yes, the one on the right, where your arrow is, is 32 lp/mm. I've used a microscope and gotten to about 52 lp/mm with a good 72 lp/mm aviation tube before. However, you need to consider that you're not using an accurate tester, and the PVS-14 lenses are not capabled of achieving the kinds of resolution you are aiming at - so what you're learning about is the limitations of the PVS-14 and who knows what the limiting resolution of the chart itself is - though given it goes up to 6x lenses, I think the tester is pretty good. So to use it as a measurement system for a tube, you'd have to build a decent relay lens system - something using a high resolution C-mount lens for machine vision , in a very small aperture. Then you'd have to set up a microscope to look directly at the screen of the tube. With that, you'd have a chance of reading the resolution of a tube as either 57 lp/mm, 64 lp/mm or 72 lp/mm. Also, keep in mind that the MTF is about 3% at that level - so the difference in the brightness of the light and dark areas of the lines will only vary by 3%. Measuring gain, on the other hand, would not be so easy - Regards David. p.s. Your photograph lacks the resolution to digitally measure the limiting resolution, but if you took a few averages at lower light levels, you could do MTF at lower resolutions by processing the image - but ideally you need raw images, not JPG compression and you'd have to adjust for the sensor also. |
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