Review: 2nd. Draft - Magni MM400

Second Draft Dec. 13/93 of article for February's TV Technology User Report on the Magni Monitor MM-400. (923 words) Underlined words at end of article do not apply to any one brand of scope but might be incorporated in this or a general article on scopes.

For some time now I have been looking for an inexpensive feature laden waveform/vectorscope without CRT (Cathode Ray Tube), that could handle Y/C, composite & component signals in loop-through mode. Magni recently filled those needs by introducing their new MM-400 which is a variation on the original Magni Monitor scope.

Magni Systems first impressed me with the quality of their "PC-to-Video Converter/Genlocks" at such affordable prices. This company seems to realize that professionals don't want to sacrifice quality or many features when paying desk top prices. The MM-400 was one of the first low priced scopes to allow the measurement of a Y/C (S video) signal in a loop-through mode. It always bothered me to work with Y/C signals, while being forced to scope the composite output. Experience has taught me that these two signals are not always output at identical levels from the same device.

The MM-400 displays a representation of a waveform or vectorscope on any picture monitor and allows a choice of colors and intensities for the display, graticule and background. Adjustment of the persistence of the display allows a full range from one field to infinite, thereby allowing capture of any glitches in the signal.

The MM-400 can scope 3 separate composite inputs or 2 can be Y/C. All 3 inputs can be used for one component channel (Y, R-Y, B-Y, Betacam or MII) or 1 analog RGB (15.75 kHz) channel, all with loop-through. That combination allows tuning of composite or Y/C devices with ease by instantly switching back and forth between input and output. In post production I will often scope the signal after each device (TBC, switcher and recorder) to see what effect each is having on the signal.

The scope can be internally referenced to any one of the three inputs or externally referenced for comparing the signals to reference or against each other in a paraded waveform display. On single channels, the waveform filters can be set for full bandwidth, low pass filter (chroma stripped), chroma filter (luma stripped) or all three can be paraded at once.

We work with S-VHS & Betacam SP, so it is important to be able to scope all the signal paths that these formats can use. In the waveform component mode, there are graticule markings indicating the limits of color bar amplitudes for the two color difference channels. This, in conjunction with an automatic interchannel timing display, gives all the information I need to check the Betacam. For my composite signal paths, the vectorscope display has SC/H phase monitoring limits as well as a color frame indicator.

Since the Magni MM-400 is lightweight, only one rack unit high and isn't mounted inside a computer, it is practical to use on a non-mobile field production shoot to help gauge exposure for creative lighting, troubleshoot or to match cameras. We always bring a monitor on field production anyway, which doubles as the scope display thereby saving weight and cost over scopes with a built-in CRT.

If the monitor being used has only one input, it can be fed from the "picture" output BNC on the Magni, thereby allowing viewing and passive switching of all inputs. This output can be set for picture, scope screens or a variable transparent combination of the two. There is also a second output used exclusively for scope readings. The MM-400 works in NTSC or PAL so video levels can be checked bidirectionally when doing standards translations. A monitor in the format being measured is required for displaying the scope.

The MM-400 uses very little power so it doesn't need a noisy fan to keep it cool. The unit is designed to be continually left on, thereby eliminating inaccuracies during warm-up.

Operators can switch from "crystal lock" to "VCR lock" for a more stable display if scoping a signal direct from a VCR without a TBC (such as an S-VHS on the record side).

Controls are on the front panel; however, Magni also provides an input for an optional remote control in case the unit can't be physically placed within arms reach.

The Magni MM-400 looks deceptively simple from its front panel and is simple when it comes to being user friendly, but it's far from being featureless. The multifunction buttons allow the operator to step through menus for many less used features or preferences. All of the regular selections are not buried in menus but accessed by a single push of a button.

The MM-400 can be automatically calibrated using the optional Magni Signal Creator or manually calibrated from the front panel with a known signal source without having to open the unit. The operator's manual was complete and had substantial application notes to teach new users how to read a scope. Magni even provides a 1-800 number for customer support.

About my only dismay with the Magni Monitor MM-400 is that you can't view the Waveform at the same time as the Vectorscope (a minor inconvenience) and that it didn't grace the market a few years earlier. Unlike some computer based, low cost "scopes on a board" that I've tried, this one isn't so basic that I will outgrow its features in the near future. Since the MM-400 isn't hosted by a computer, the screen doesn't have to be shared with the scope, it doesn't tax the computer's power supply and the scope is very transportable. In my opinion, the MM-400 is a solid performer with a wide range of features that should appeal to a variety of users.

BIO
Doug Hembruff is the President of Impact Televideo Productions in London, Ontario, Canada. He facilitates corporate and broadcast video production, as well as product evaluation, writing, beta testing and consulting.

Computer artists creating graphics or animation for video, often view only an RGB screen. Specifying video IRE levels improve the odds that you're going to get what you want, and using a vectorscope minimizes the chance of getting illegal colors.

One of the tricks to lossless importation of video into any 24 bit paint or processing program, is to ensure that the luma and chroma levels are within legal limits. 24 bit computer programs deal with 256 discrete levels of red, green and blue ranging from 7 IRE to 100. Anything outside those limits is trashed and causes a loss in detail of the black or white areas as well as a reduction of color saturation in spots. For more info contact Doug Hembruff.