Test Equipment Anonymous (TEA) group therapy thread

[tggzzz]

35mm film isn’t very big and the resolution isn’t very high. The grain limits that.

The resolution of film is surprisingly high, on the right film of course. Fuji Velvia (colour slide, 50 ASA) would resolve 160 line pairs/mm. Specialist monochrome films like Ilford PanF and Kodak Technical Pan could be pushed with careful and specialised processing to close to 1000 line pairs/mm. (That's rated at 12 ASA or even lower.)

Taking the 160 lp/mm: you have to double that to get the equivalent digital resolution (line pairs remember), so 320 dots/mm. The 35 mm frame is 24mm x 36mm, so that gives you a resolution of ~88.5 Mpixels. The truth is that no lens, not even Angénieux or Zeiss's priciest lumps of glass, could ever make full use of that resolution. Good professional SLR lenses typically deliver on the close order of ~30 line pairs/mm with a MTF of 0.5 at the centre (can be much worse at the edges).

It's no accident that the first professional digital 35mm cameras that gained wide acceptance were the 3 Mpixel ones like the Nikon D1, that's the magic point where most of the practical resolution of lenses on 35mm film gets transferred to the digital image. 6 Mpixels is probably a bit better than the lens, 12 Mpixels definitely exceeds the capability of the lenses, anything beyond that is pure marketing wank. This obviously isn't the case for physically bigger sensors such as the professional 6x6cm sensors, it only holds for 35mm size systems.

I'm with tgzzz on practical resolution. Back in the day, when we sent transparencies (6cm x 6cm, 5 x 4 in) out for drum scanning it wasn't worth going beyond 2400-3000 lines per inch on the film. By the time you'd got there you'd captured all the detail that the lens had managed to deliver.

The 35mm images I was digitising at 5000x3000 were very carefully selected digital images, for resale. Great care was required, e.g. they were all manually despotted after digitisation!

I quite agree about your resolution for "ordinary" images.

[Specmaster]

That Keithley brown seems to have been multiplying in my lab the past couple of years. Something different from the usual bench-gear black, silver, and gray, I suppose.

Phillip's also have some brown items among their earlier ranges, got any?

[tggzzz]

Currently the 2MB SMF limit is fit for purpose.

That's the key point.

There are a few and relatively rare use-cases for large image files (N.B. != high resolution, of course). Those can be satisfied by using an external storage mechanism.

Most uses can be perfectly well satisfied with a broad view and detailed closeups, and in many cases that is preferable to a single large image.

Having "small" images forces posters to think about what is actually useful for the reader, and that's A Good Thing.

[Specmaster]

Bonus points for the TEA addict who correctly identifies the ware in the photo.

HP or Agsight bench DMM, dunno which model. 

No, yes. 

Hints: old, (circa 1980) and British.

OK here's my guess on the make, and I'll come back to you on the model.

The make Thurlby Thander or as they became TTi Ltd.

Or it could be a Gould Advance Gamma meter?

[tautech]

Bonus points for the TEA addict who correctly identifies the ware in the photo.

HP or Agsight bench DMM, dunno which model. 

No, yes. 

Hints: old, (circa 1980) and British.

DMM was the easy bit as the divider networks are plainly visible. 

[bd139]

Gould. Recognise the beige and the transformer covered in spooge.

[Specmaster]

@Cerebus, Ok here goes, I'm going with the make and model of the DMM in your photo as being a Gould Alpha, not the III model as that only had 2 switch wafers but its a Gould for sure and that brown box at the back is the battery compartment. 

[PA0PBZ]

Yes it's a Gould but I am unable to find the model. All I can find is the Alpha III that has no AC option and the pcb differs a lot:



Maybe it is the Beta but I could not find any pcb pictures for that one.

[Specmaster]

Yes it's a Gould but I am unable to find the model. All I can find is the Alpha III that has no AC option and the pcb differs a lot:



Maybe it is the Beta but I could not find any pcb pictures for that one.

The Beta like the Alpha III only has 2 switch wafers and no AC power option being powered by battery and/or a wall wart.

[PA0PBZ]

The Beta like the Alpha III only has 2 switch wafers and no AC power option being powered by battery and/or a wall wart.

Ok, that makes sense, it looked like radiomuseum used the same picture for the Beta but then I guess they look the same.

[Specmaster]

The Beta like the Alpha III only has 2 switch wafers and no AC power option being powered by battery and/or a wall wart.

Ok, that makes sense, it looked like radiomuseum used the same picture for the Beta but then I guess they look the same.

Well it could either one of those models as they may have had variations of them but info on that makers products is like hens teeth, but one thing for sure is thats from the Gould range, hopefully Cerebus will put us out of our misery soon 

[Specmaster]

The Beta like the Alpha III only has 2 switch wafers and no AC power option being powered by battery and/or a wall wart.

Ok, that makes sense, it looked like radiomuseum used the same picture for the Beta but then I guess they look the same.

It seems that I could even be right with my first guess of it being a Gould Gamma as photo shows, problem is though I don't think the Gamma had a battery option but I could be wrong on that.

[PA0PBZ]

It seems that I could even be right with my first guess of it being a Gould Gamma as photo shows, problem is though I don't think the Gamma had a battery option but I could be wrong on that.

I searched for the Gamma since we already had Alpha and Beta but I did not get any hits. So until Cerebus chimes in it's a Schrödinger Gamma.

[mnementh]

It seems that I could even be right with my first guess of it being a Gould Gamma as photo shows, problem is though I don't think the Gamma had a battery option but I could be wrong on that.

I searched for the Gamma since we already had Alpha and Beta but I did not get any hits. So until Cerebus chimes in it's a Schrödinger Gamma.

Still coffee-ing. In that dim, barely conscious hypnagogic state before warmth in my belly and caffeine have a chance to work, I am reminded me of a favorite from my youth...



mnem
"I HAVE RESERVATIONS ABOUT RECONCILING A QUANTUM MECHANICS THOUGHT EXPERIMENT WITH EGYPTIAN MYTHOLOGY."

[Cerebus]

35mm film isn’t very big and the resolution isn’t very high. The grain limits that.

The resolution of film is surprisingly high, on the right film of course. Fuji Velvia (colour slide, 50 ASA) would resolve 160 line pairs/mm. Specialist monochrome films like Ilford PanF and Kodak Technical Pan could be pushed with careful and specialised processing to close to 1000 line pairs/mm. (That's rated at 12 ASA or even lower.)

Taking the 160 lp/mm: you have to double that to get the equivalent digital resolution (line pairs remember), so 320 dots/mm. The 35 mm frame is 24mm x 36mm, so that gives you a resolution of ~88.5 Mpixels. The truth is that no lens, not even Angénieux or Zeiss's priciest lumps of glass, could ever make full use of that resolution. Good professional SLR lenses typically deliver on the close order of ~30 line pairs/mm with a MTF of 0.5 at the centre (can be much worse at the edges).

It's no accident that the first professional digital 35mm cameras that gained wide acceptance were the 3 Mpixel ones like the Nikon D1, that's the magic point where most of the practical resolution of lenses on 35mm film gets transferred to the digital image. 6 Mpixels is probably a bit better than the lens, 12 Mpixels definitely exceeds the capability of the lenses, anything beyond that is pure marketing wank. This obviously isn't the case for physically bigger sensors such as the professional 6x6cm sensors, it only holds for 35mm size systems.

I'm with tgzzz on practical resolution. Back in the day, when we sent transparencies (6cm x 6cm, 5 x 4 in) out for drum scanning it wasn't worth going beyond 2400-3000 lines per inch on the film. By the time you'd got there you'd captured all the detail that the lens had managed to deliver.

The 35mm images I was digitising at 5000x3000 were very carefully selected digital images, for resale. Great care was required, e.g. they were all manually despotted after digitisation!

I quite agree about your resolution for "ordinary" images.

Eh? I'm suggesting 2400-3000 lpi on large negatives and you're suggesting ~3500 lpi on 35mm negatives. That's essentially the same as your point of view but it sounds like you think I'm suggesting something different. (FWIW the specific class of examples I'm drawing on would have been routinely manually despotted after digitisation too - one doesn't want a dirty great dust spot on someone's nose on a magazine cover).

[Cerebus]

Or it could be a Gould Advance Gamma meter?

Bingo! Made in Gould's Essex factory about, oh, three miles from where I'm sitting at the moment. Now gone, and I believe the estate in question is currently at risk of being turned into luxury flats (as is every other scrap of usable land around here at the moment, Stratford High Street is beginning to look like a stretch of any US cities' downtown residential district.)

For your no-prize I cede my rights to use the words "defenestrate", "autodefenestrate", and the phrase "trans-fenestral situations" on the forum to you for one whole week! 

[Ero-Shan]

The only things on that table that looks remotely interesting are a few power supplies, but hey, how many do you need? I have 2 (cheap ones admittedly) but seldom use them and there what looks like some phillips CRO's.

I need a good 20A 12V supply at the moment so win there possibly.

That would be a nice job for my hp 6032A. At 12 V it can supply 50 A. But that boat anchor is not fit for everyday use on the lab bench ...

[tggzzz]

Eh? I'm suggesting 2400-3000 lpi on large negatives and you're suggesting ~3500 lpi on 35mm negatives. That's essentially the same as your point of view but it sounds like you think I'm suggesting something different. (FWIW the specific class of examples I'm drawing on would have been routinely manually despotted after digitisation too - one doesn't want a dirty great dust spot on someone's nose on a magazine cover).

OK; I missed the "per inch" and didn't do any arithmetic.

The point about someone's nose is also spot on (ho ho) and directly applicable!

[Specmaster]

Or it could be a Gould Advance Gamma meter?

Bingo! Made in Gould's Essex factory about, oh, three miles from where I'm sitting at the moment. Now gone, and I believe the estate in question is currently at risk of being turned into luxury flats (as is every other scrap of usable land around here at the moment, Stratford High Street is beginning to look like a stretch of any US cities' downtown residential district.)

For your no-prize I cede my rights to use the words "defenestrate", "autodefenestrate", and the phrase "trans-fenestral situations" on the forum to you for one whole week! 

Or in other words, business as normal 

Yes its a crying shame that they went, I used to call on their electrical engineers many years ago, how times change 

[Cerebus]

Or it could be a Gould Advance Gamma meter?

Bingo! Made in Gould's Essex factory about, oh, three miles from where I'm sitting at the moment. Now gone, and I believe the estate in question is currently at risk of being turned into luxury flats (as is every other scrap of usable land around here at the moment, Stratford High Street is beginning to look like a stretch of any US cities' downtown residential district.)

For your no-prize I cede my rights to use the words "defenestrate", "autodefenestrate", and the phrase "trans-fenestral situations" on the forum to you for one whole week! 

Or in other words, business as normal 

Yes its a crying shame that they went, I used to call on their electrical engineers many years ago, how times change 

I did say it was a no-prize^{© Stan Lee}!

Proper photos to follow in my next post.

[Cerebus]

Specmaster correctly identified this



as a Gould Gamma True RMS Multimeter, here with its clothes on:



I bought it about a year ago off the 'bay for a song - I don't think I spent a tenner, and it certainly wasn't over £15. The original intention was to gut it and reuse the rather fine aluminium case and tilting bail. It was sold 'spares and repairs' untested and with the dodgy looking LCD I suspected that it was a deader. In fact it's working, agrees within 1 count or two with my other 3 ¹/₂ digit meters; so as such I haven't yet had the heart to re-purpose it as originally intended. The LCD is rather 'orrible and if I'm going to keep it in working condition I'll have to track down a compatible display and install that.

For the afficianardos, the "True RMS" element is a ceramic, gold plated AD536JD and the voltage reference is a very ordinary looking BZX79C zener, which I expect was selected and carefully burned in given its otherwise pedestrian specification.

Here is the full set of pics, shot rather hastily this afternoon to compensate for all my wibbling about JPEG sizes and to "keep it TEA".





Note the dual power. I've never tried it on batteries as I don't keep C/SP11/HP11 cells around the house.

[xrunner]

What's the little jack used for on the right side?

[Specmaster]

@Cerebus, you might be in luck but it could cost you more than the tenner you paid, take a look here https://www.ebay.co.uk/itm/Gould-Advance-Gamma-RMS-Multimeter/352439577436

Hopefully you might be able to do a deal and keep this piece of Essex history alive.

[Specmaster]

What's the little jack used for on the right side?

I would guess its for a 6v wall wart, is that correct Cerebus?

[neo]

Currently the 2MB SMF limit is fit for purpose.

Exactly.  It’s rare more detail is needed. If so link to an outside site. Many of us do not have fast pipes. I’m limited to about 1 Mbs most if the time at home. Many others are in the same boat.

Including me.

Also.... UGH! CAMERA TALK! 

If this keeps up there may be a prodigious defenestration following by an auto defenestration