EEVblog Electronics Community Forum
Products => Thermal Imaging => Topic started by: Sikastina on July 02, 2020, 09:51:31 pm
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First thank you for all of the content and youtube videos the community shares. I will definitely be reading an learning more from the volumes of information here.
I'm looking to play around in the infrared range and willing to spend up to ~$1,000ish while learning/playing with a new toy that also has actual usage too. In addition to being a new platform to learn from I'll certainly be looking around my home for HVAC, recessed lighting attic leaks, and other energy efficiency aspects; and then as another tool at my disposal to do diagnostics with as opportunities arise... all which if I only wanted to spot check an AC for example I know I could accomplish with a great many devices for well under a $1,000 budget. My thought is that expanding my budget beyond the $500 threshold opens up more opportunity.
In reading around the boards and webbernet I'm seeing what appear to be two really good options that provide two very different worlds to learn and explore with. The E4 or one of the 384x288 phone modules... likely the HTI-301 since it seems most readily available (though I would consider the other dongles by Xtherm T3 or Thermal Expert TE lines if there was a decent source for them I've messaged both for pricing but haven't heard back).
So my thoughts so far on the options:
E4 (upgraded of course)
- I have plenty of experience with flashing the firmware on my routers and android phones to custom builds, so I'm not intimidated by the upgrade process to get the E8 features... if anything it seems like it may actually be easier.
- Real Thermography data to challenge myself to learn more about
- Proven tool with lots of support and resources available
- Durable and built to last
- Will always have resale value if I decide to move on or upgrade
If I go this route, I'm seeing different posts from different points in time as to whether all E4's are upgradeable or if the newer firmware's don't allow the upgrade?
HTI-301 (or other 384x288 phone module)
- Access to sensor pixel count for what looks like less money than E4
- Portability (after all the best camera is the one you have with you)
- Manual focus
- More photography exploration/freedom
- Potentially more hassle dealing with apps and less refined systems
Any suggestions or thoughts on these two options? Other aspects you would share with a curious hobbyist?
Edited to fix bullets
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Another disadvantage for E4, the framerate is capped to 9Hz (not sure whether is hackable) due to some ITAR regulation (which is nonsense to me as it's easy enough to get unlimited sensors from ULIS or China). HT-301 or identical Chinese dongles are at 25Hz refresh rate, so they are probably better for animal spotting. However, if your use case is only static scene, either HT301 or E4 can be good.
The temperature sensitivity of HT-301 is likely to be slightly inferior to the E4 from NETD in the datasheet.
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Excellent point... the HT-301 would offer video as an advantage.
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Having a little experience in thermal photography from an artistic viewpoint, using a range of devices, I have found these things important.
Manual focus
Manual span / range (=exposure)
Lowest possible NETD
Decent resolution
Narrow field of view(*)
Fast frame rate
Interchangeable lenses
Easy access to saved images
The reason for wanting manual focus is fairly obvious, although now that ZnSe close-focus lenses are readily available that don't dent the sensitivity to any great extent.
Manual exposure is critical for repeatability and is essential if you plan to use multiple exposures to lower noise or to stitch a panorama.
Lowest NETD gives better sensitivity to small temperature differences (='contrast resolution'). To a certain extent you can compensate by averaging multiple exposures but the tedium increases exponentially with improvement in results.
Resolution appears self-explanatory, but it's actually intertwined with field of view. You can make better images with a 160x128 with (say) 8° field of view than you can with a much more expensive 640x480 with (say) 45° field of view. It just takes longer, because you need to make and then stitch multiple exposures. I'd regard 320x240 as minimum acceptable; 384x288 may not sound that much of an improvement but has about 50% more pixels than 320x240. 640x480 is very, very nice.
Fast frame rate may seem irrelevant if you're only talking about still images but it takes much longer to get sharp (manual) focus on a low frame rate camera - the relationship is not linear.
Interchangeable lenses give you flexibility. Given that zoom lenses are rare and unaffordable, being able to change from medium-wide to normal to medium telephoto gives you a lot of scope to do things like force perspective. You can also exploit the different depth of focus afforded by different focal lengths and apertures. There aren't many variable aperture lenses for uncooled LWIR sensors.
Easy access to saved images seems like a no-brainer, but I have a couple of cameras where saving and recalling images is either extremely difficult or impossible.
If I think of anything else I'll post it.