As every SVHS user must have noticed, genuine SVHS video cassettes are considerably more expensive than VHS cassettes are. For some time I have been punching a hole in the base of VHS cassettes to use for less than critical applications, but have not been entirely happy with the results. I present here my initial reactions gained from using these tapes, and also images from an oscilloscope of the result of using various different cassettes to record and replay a test card.
My initial reactions to various punched cassettes were that it appeared that punched cassettes were inferior in the following ways:
Note that these observations were made with a monitor which has better high frequency performance than any TV which I have used. The HF related problems will not be so visible on an average TV.
I have tried punching a number of different VHS tapes:
The BASF Vision (especially at the price) and Scotch EXG+ gave perhaps the best results.
On the other hand, I've also used a number of different SVHS tapes, which I have found give generally good results ( better than any converted tape ):
More recently, I have tried to measure the performance of some tapes. I did this by connecting my laser disc player to the SVHS recorder and trying out recording he "multiburst" test signal from the "Video Essentials" laserdisc (frame 46619 on side 2) on a selection of different tapes. The signal direct from the laserdisc player looked like this:
While it is obvious that this output isn't completely flat, the best possible result for any recorder would be to exactly reproduce this waveform. This is how they actually got on:
|BASF SVHS||BASF SVHS recorded as VHS|
|TDK XP SVHS||TDK XP SVHS recorded as VHS|
|Scotch EXG+, punched for SVHS||Scotch EXG+, recorded as VHS|
|BASF Vision, punched for SVHS||BASF Vision, recorded as VHS|
|TDK TV, punched for SVHS||TDK TV, recorded as VHS|
|Memorex SHQ punched for SVHS||Memorex SHQ recorded as VHS|
|Free Radio Times Promotional tape||ree Radio Times promotional recorded as VHS|
|'Noddy' tape punched as SVHS||'Noddy' tape recorded as VHS|
Note that even the children's 'Noddy' tape (red plastic, 60m length) and the Radio Times freebie have reasonably similar performance to the more expensive VHS tapes.
Here once again for comparison is the original signal, and an SVHS copy:
Note that even a good SVHS tape doesn't capture the highest frequencies (the right most burst of the multiburst) on the disc. My subjective impression had been that SVHS recordings lacked the definition of good broadcast video (which generally has decently high bandwidth in the UK). Also note that the signal looks ragged in comparison to the laserdisc, which I take to be an increase in noise. Noise on the VHS tapes punched to enable SVHS recordings to be made are obviously more "ragged", and visibly more noisy. VHS tapes give better signal to noise performance when used un-punched. It is also noteworthy that the SVHS tapes have slightly worse high frequency response than "proper" VHS tapes when used to record VHS signals, so the use of an expensive SVHS cassette cannot be expected to bring performance improvements for VHS users.
I will probably continue to use the better punched tapes for SVHS recordings. While there is visible extra noise, especially at higher frequencies, on most material the extra bandwidth of the SVHS recording is a worthwhile improvement. The obviously limited resolution of VHS (as below) produces a remarkably murky picture.
My new video tape purchases will all be of SVHS tapes.
Equipment used to produce the test signal, record it and play it back.
To produce the graphics for this page:
The latter combination is largely responsible for the relative lack of quality of the images. If anyone out there is willing to give me a digital camera, I'll do it all again...
This document and the images within it are copyright David Hembrow, 1998.
When this was written, SVHS was relevant and SVHS-ET, which allowed use of non punched tapes for SVHS recording on later SVHS recorders, had not yet appeared. These days it all seems like a distant memory. I do now own a digital camera...
I also have some pages about hifi.
I work as a willow basketmaker. You can see examples of my work here. During the summer I organise cycling holidays in the Netherlands.