I have a pair of these older general electric F36W/33's, which I salvaged from a junk box a while ago. They appear very low hour, and I'm currently using them together with a pair of Sylvania activa 172's. I am using one of each per light fixture, and it provides a truly excellent mix of 4000K and 6500K light, and the light quality appears absolutely amazing! I'm super happy with the results of mixing the two! The light output from the general electric tubes appear just as high quality as the Sylvania Activa's when I run them alone for a test, so this makes me wonder if they are high CRI tubes too! I'd love you guys input on this, I am not able to find much information about these tubes. I got a great logo shot though through my light covers without having to take them off

/33 was one of those mildly enhanced 'office' halophosphate colors of around 3600K and around 70CRI. Pretty much nothing to rave about, honestly...

Update - actually, typically rated of CRI64, so even worse...

Aw, still a nice tube though although I probably shouldn’t use it for my main lights if the CRI is only 70. all T8 bulbs are precious these days since stocks seem to deplete really fast at all my suppliers. I wanted to purchase some more 830 tubes the other day, and all my usual suppliers were completely out. I’m definitely going to install something else though to mix with the activa, because 70 CRI is quite poor. I’m also thinking about going back to 840 tubes because as I spent more time there last night my eyes started getting sore, I really can’t handle higher colour temperatures for some reason, but I really wish I could because high CRI tubes are usually all in the 5000-6500 range.

(Edit) Wow, if they are really that poor then I’m gonna take them out of service immediately and put them into use for a storage area where high CRI is not a concern instead, I didn’t think they were that bad actually. I was caught off guard thanks to their lower lumen output of just 2850 instead of the typical 3350. That made me think it had a fancier phosphour than it clearly does, hehe

May be you should invest in a pocket spectrometer like I did if you have such a great interest in light sources. Yep spectral resolution is not so great, but these are calibrated out of the box and still quite good (I confirm) at guessing CCT and CRI. Basically you know what lamp you are dealing within a button press and a few seconds. Also these instruments are useful as light meters.





 

That sounds really nice, I should definitely get one of those I've always been very deeply interested in fluorescent tubes and their different phosphorus coatings, that's why I swap tubes so often haha. I enjoy experiencing different colours

Which model do you have? A pocket spectrometer sounds great, I probably don't need crazy accuracy for my little funs, I just want to know if im dealing with CRI 80,85,90 or higher really, that's all the testing I wanna do more or less a lux meter is also a nice bonus!

Mine is named HP320 from Chinese brand Duotone Cloud. Got it at about $300 from Aliexpress.
There is also a slightly more expensive HP350 with a bit better resolution.

Yoy can see some samples of what results I am getting with this instrument here: https://www.lighting-gallery.net/gallery/displayimage.php?pos=-240046

I just want to know if im dealing with CRI 80,85,90 or higher really

James' site provides all the information you need: https://www.lamptech.co.uk/Documents/FL%20Colours.htm

33 is also known as 640, which means 60-69 CRI and a 4000k color temperature.

You might be confused with the color 25 (a.k.a. 740) 'Natural' or 'Universal  4000k 75 cri halophosphate lamps that are very similar, but slightly improved.

If you want to know just the color temperature, your smartphone's camera is likely to be able to measure it. If i put my cheap Motorola's camera on fully controllable mode with the exception of the white balance, i can see the white point temperature get very close. In fact, the first picture is absolutely spot on (930 fluorescent). The 2nd one i can't tell what it should be, but it's indirect daylight from a partially overcast sky, filtered through vitrage, on common white wall paint. But with 5500k it is likely very close.

Camera algorithm is sure very good at setting neutral color balance in the image, but in principle can not retrieve a reliable CCT value from just 3 readings of sensor RGB channels. You may get some likely values from continuous spectrum sources, especially resembling incandescent light as in your examples, but point the camera to something with peaky spectrum like metal halide or triphosphor fluorescent lamp, and I expect some gross errors in CCT value.

It's not bad, really. A 33/640 tube measured 4000k which should be good. A 29/530 tube sat at 2800 which is a small but significant difference, but one must take into account that the camera might also be slightly influenced by red or blue colored objects in the surroundings.

I haven't tried coated MV lamps or triphosphor 8xx fluorescents yet.