Hi Walt,
I'm no expert on borescopes but I can perhaps share my experience to add some weight to your thoughts...
I bought an eBay device for use with iPhone and iPad, and I guess for the money (about £50 iirc) it's ok - it did the job I needed it to do, which was some preliminary inspection work to see of there was anything obvious amiss with my engine before plunging for the tear-down option. And for this, it did give me good enough resolution to see the condition of the bores and piston tops.
But...would I want to use this on a more frequent basis than I have so far? No.
Mine uses WiFi - it creates it's own access point, to which you pair the iOS device. I know not why, but this is terribly intermittent. Once the signal drops, it's a case of starting all over. REALLY irritating when you've just about manoeuvred the lens into the position you need.
The focal length is exactly as you say - limiting. For our use, this is crucial, and I'd have to dig out the specs on mine to tell you what it is, but suffice to say, don't skimp on this bit. (I thought mine would be fine when I bought it, but in reality it's adequate at best @30mm). The viewing angle on mine is 66º.
The outer ring of LEDs are ok....the only occasion when you don't want them at full brightness is when using with the 45º mirror attachment, as it over exposes the image against the mirror-like cylinder walls! The rotary switch on mine is a little binary; it also acts as the on/off switch, so I have a feeling that this is intermittent and triggering the unit to "blip" causing it to lose WiFi connectivity (hence Prob #1)
On the plus-side:
- the diameter of the lens assy is great - fine for spark plug entry and everything I've thrown at it.
- the flexi-neck is also very good; rigid enough to hold position.
- one press of the units button forces the iOS device to capture the image, so you can generally "get" the pic you want without shake or inadvertently moving the frame.
- picture quality on the iPad was really quite good (I'll dig out some pics later)
The 45º mirror for 90º viewing isn't too bad, not sure if there are units out there with a selection of angles in their kit-of-bits; this would definitely be useful. Something approaching a 180º view would be excellent for head/valve shots - this may be wishful thinking though!
Having briefly used an industrial grade Olympus setup, it is a marked difference...with an eyepiece over the inspection tube, it's ok for cylinder inspection - but I've used my camera for rooting around in the engine bay (dropped nut) and crankcase - the Olympus would be no good for that. The Olympus had an infinitely variable twist and rotate head, very cool...but also cost a fortune to buy and maintain. It had a separate light box and fibre optic "hose" = massively expensive for bulbs and new fibres as/when they get damaged! Images also couldn't be captured.
If I were doing it again, I would go for a hard-wired USB device, definitely with a rigid neck and I'd invest more into something with a tighter focal length. I'm not sure if that's possible, I guess the majority of them use exactly the same CCD chips.
HTH
Spencer.
Edited to add...
Just searched my Inbox - I paid £55, and upon clicking the link, it's now down to £36! Typical. For $45, maybe worth a punt?
This is the one which I bought....
...with this spec...
Manufacturer Specifications
Model No: 99W2
Certification: CE, ROHS, FCC
Len pixels: 1280*720/ 1600*1200/ 640*480
Len Dia.: 8.5mm
Removable Tuble Dia.: 6.8mm
RemoveableTube length:800mm
Focus distance:30mm to 80mm
View angle:66
Frame Rate: 30fps
Security: Password Setup
Receiver distance: 20M
Accessories: mirror, hook, magnet
Powered by : 4 pcs AA batteries(not included)