There isn’t HD versions of SG1 until season 8…
This is an interesting case.
Seasons 1-3 were shot on 16mm, scanned and edited on composite digital D-3 tape. Therefore, these masters are forever locked to 480i composite NTSC resolution. Even if they get rescanned and re-edited, 16mm film does not offer much more resolution than SD. They could however edit them in component digital 4:2:2 format and master them in SD progressive scan.
They were originally broadcasted in 4:3 open matte ratio. D-3 master tape was converted to D-1 component and matted to 16:9 for the DVD release. This process doesn't doesn't add any improvements to video.
I have the Laserdisc release for the pilot episode which is the only open matte 4:3 home release. It also has the Dolby Stereo broadcast soundtrack in uncompressed PCM. Unfortunately, they released only the pilot on Laserdisc.
Seasons 4-7 were shot on 32mm, scanned and edited on composite digital D-3 tape. D-1 format was super expensive and was rarely used for TV. Although 32mm offers much higher resolution, the final master is bottlenecked by the D-3 tape and has similar video quality to the first 3 seasons except some finer grain (32mm vs 16mm). Season 4 and 5 were broadcasted in open matte 4:3 ratio but matted to 16:9 for the DVDs. Seasons 6 and 7 were broadcasted in HD and in 16:9 ratio. These might be on D-1 or better mastering tape. I don't have any info on this.
Season 8-10 were shot on HDCAM and mastered in 1080p24. All shots were composed for 16:9 ratio.
Let's look at the home video releases. All seasons were released on DVD. Most season episodes were spread on 5 DVD-9 discs which roughly 40GB of data per season.
There is a recent box set release in Blu-ray disc format. The video on these discs are upconverted from SD masters for the first 5 seasons. Almost identical to the earlier DVD releases. Season 6 and 7 also have poor video quality and might be upconverted from SD too. Season 8 to 10 are natively HD. There is a mastering flaw on the audio soundtracks. They are on lossy Dolby Digital encodes to begin with. The rear channels are faux surround and not natively discreet. The early DVD releases also had Dolby Digital encodes but they were in true discreet 5.1.
Now let's look at the Kaleidescape releases. Season 1 and 3 are in SD. The store does not specify the audio soundtracks. It is safe to assume, you get the Dolby Stereo and Dolby Digital soundtracks as common with most SD releases. The question is if the K release has the correct Dolby Digital soundtrack or the flawed one like in the Blu-ray disc release. Another curious point is the K version is 70GB for the season 1 and 80GB for the seasons 2 and 3. This is double the DVD releases. Does this mean the original 16mm films were rescanned and remastered in digital component 4:2:2 format? I think the data size increase indicates that. If this is true, and the Dolby soundtrack is the true discreet mix, the K version is the definitive home video release even in SD resolution. Perhaps, I should bite the bullet on purchasing the K versions and compare all. My only worry is the possibility of the flawed audio soundtrack.
Apologies for the lengthy post. I am a bit enthusiastic about the 90s/00s sci-fi TV shows. I hope someone from Kaleidescape can provide a little more information about the master they used