I was wondering how much you really gain by going with 320x240 IR resolution v. the (old) standard 160x120. I can see where it might come in handy if you're examining very fine, or very distant, objects. I've heard raves about the higher resolution anything less will simply not perform. On the other hand, I've heard experienced thermographers say that the increased resolution was not something that is crucial to the success of an IR program.

Are there any of you that have upgraded to a higher res camera recently and thought that it was definitely worth it, and it helped you to analyze and pick out problem areas quicker and more accurately?

Firstly, the 320x240 is the industry standard. The 120x160 have been introduced to meet demand for lower prices, and they have done that very well, introducing thermography to a new generation of users.

I think you do however ask the wrong question. The correct question is " Are there any of you that have downgraged to a 120x160? And if so has there been a noticeable reduction in the level of service you provide?"

The NEW standard for infrared thermography will be a 640x480 for higher definition cameras as recently introduced http://www.bestininfrared.com and in the next few years we can expect even lower resolution equipment to emerge, I am already aware of a 60x80 camera and a 16x16 camera.

Bob - great points! Thanks.

Vendor warning: Bestininfrared.com is a FLIR web site - not exactly the most independent source for information. Funny that they do not label it clearly but it is not too difficult to figure out who is behind the site.

Terry O

Hi Sam, in answer to your question, I have the opportunity to regularly use both 160x120 and 320x240 cameras.
The benefit in terms of image quality is clear - assuming that the optical design of the camera is good enough. I have seen some cameras that produce better images in 160x120 than in the higher mode. Just like in digital cameras, megapixels is not everything and a bigger detector cannot overcome the inherent diability caused by poor optics.
Since I have never used both cameras simultaneously, I cannot say if there is a problem which would be visible to one but not the other - in terms of electrical inspections I would be amazed if it would.
In a nutshell, change if you want to, but I really do not feel that resolution can be a wholly justifiable reason.
I hope that the camera companies won't put a price on my head for saying that!
Best Regards,
Tom Murphy

Try the link above. It gives a great demo on the differences in temperatures detected using the different resolutions.

The demo does use an inspection from a distance (overhead T/D) as an example, though. I'm not sure if you were one foot away (MCC inspection), if there would differences like in the example.

Resolution depends not only on the number of pixels in the detector, but also the lens (or optical path) and the distance. Clearly in the demo referenced above, and in many cases, you cannot get closer.

By adding a telephoto lens to a camera with ANY detector, resolution will improve. At the same time field of view (FOV)will become more narrow. The primary benefit of the 640 systems is that one can have fairly high resolution and a large FOV at the same time.

I would caution that the demo, and many thermographers, emphasizes the value of temperature measurement over simple detection. In a substation, I'd say we are way ahead even if we only detect a problem. Clearly there may be advantages to a more detailed image that allows use to see more precisely what is going on.

Regarding temperature measurement, improved spatial resolution does also typically bring with it improved measurement resolution. That said, measurement reliability and usefullness—regardless of the IR system—are typically extremently low compared to what most believe about them! Emissivity, background, load (current and future), wind, and thermal gradient all quickly take their toll. Even when measurements are reliable, we often do truly understand what they mean about impending failure.

Too many of us have been suckered into believing temperatures should be the primary concern. Of far greater importance, in my mind, is making sure conditions are right so that, if a problem actually exists, we can detect it. Once detected, we may be able to determine temperature values and they may be useful in analysis.

Thermally yours,

John

One other thing, here are two images shot side by side using the camera AUTO adjust features. One is a 160 and the other a 320. (I don't yet have an image from a 640 for comparison.)

Even though I would probably have better measurement resolution with the 320 system, I'd be happy with either one!

Thermally yours,

John

John

Thanks for the posting - the image you feature is a TIF format and is not browser friendly.

Web browsers like JPG, GIF and PNG.

Can you re-post as we have had a few requests.

I converted to JPG but I am not sure if the resolution is clear enough to make John's point.

Thanks,
Terry O

This message has been edited. Last edited by: Terrence O'Hanlon,

Sorry about that! Here is a JPG that should behave better.

Great comparison!
Obviously the higher resolution looks crisper (I like it!), but I'd have a hard time saying that the lower resolution camera is 'incapable' by any stretch of the word. In my eyes, I don't see why you can't perform effective measurements on a lower resolution camera. If I were a freelance thermographer, I would probably spring for the extra res. But I figure, I'll save the extra cash and buy into ultrasound as well.

quote:

I don't see why you can't perform effective measurements on a lower resolution camera.

Seeing a problem and measuring are two different things totally. Very often we can see problems that we cannot measure, this is not always down to resolution, but if you are thinking at measuring small targets, or targets a bit away you should consider a higher resolution imager.

Ask yourself, "what is the smallest target I am likely to need to measure"? Then ask yourself, "how close am I going to be able to get to that target"? Then build a simulated target and test a few cameras on it. Think about how much accuracy you may need, it is surprising how much difference there is between cameras on the same target.

Good point Bob; it was a poor choice of words. It was one of the things I weighed before buying our camera: How small of a spatial resolution do I really need? For our purposes, I didn't see us using it for anything far field that we couldn't get physically closer to.

A 160x120 camera usally gives about 2.5 mrad of resolution. The way I understand this, that would imply that the camera takes an average reading (ie, an inaccuracy) over a 3cm dia 'dot' at a distance of about 12 meters. I'm convinced this is plenty in order to at least identify a problem. If a problem IS detected from relatively far away, we are able to get much closer to 95% of the locations in our plant in order to take better quantitative measurements.

SSR or Spot Size Ratio is usually the easiest way to understand specfiications. A typical 120x160 should have an SSR of about 110:1. This means that you should be able to measure a 1 inch target at about 100 inches, and a 0.5 inch target at about 50 inches and so on. This can be significantly better on 320x240 where the SSR can be as much as 300:1.

John,

I have to admit I am not a pro in IR, but I do agree, in general, higher resolution results in ability of smaller details to become discernable.

The image above, though, taken with a lower resolution camera seems to be taken rather with misadjusted focus. This could be clearly seen by looking at the outlines of the large object - apparently a transformer - with the borders not being sharp. Is that a result of low resolution?

David

David

Both were taken as fairly as possible using best focus and best adjustment of level and span. Interestingly, I have not revealed which is which!

Clearly with the 160x120 system there is less detail (for both spatial and measurement resolution) than there is with a 320x240 system. I'm not suggesting one is necessarily better than the other; rather I'm saying consider what our real needs are and then buy appropriately.

Sam,

Mikron has a so called Lens calculator on their site.
If you input resolution, distance to the object, camera view angle, etc. you'll get the smallest area size on the object the camera can resolve.

I guess this is exactly what a practioner needs in order to make an intelligent decision on what resolution is needed for a particular application. Why pay for something you really don't need?

David

This message has been edited. Last edited by: David_G,