Short-term exposure to frequencies in the 3Hz to 70Hz range are associated with epileptic seizures, with the highest possibility of occurrence being in the 15Hz to 20Hz range. There are health concerns with visible flickering. It is considered that anything below a frequency of 100Hz can be seen. Obviously visible flicker is the one our eyes can see, which is when the light output from a given source changes rapidly. There are two types of flickering with lights – visible flicker and invisible flicker. What are the causes of this, and are there solutions? Types of Flickering Despite flickering being less present in LED than with fluorescent systems, it is certainly still a factor. And it can make a world of difference.With fluorescent lighting gradually being displaced in favor of LED, many thought the days of dealing with flickering lights were over. End titles are generally delivered at 100% white, but in a dark theater, absent any other elements, even 60-70% grey will still read as white. Using more columns and doubling up blocks where possible will reduce your end titles’ vertical size and allow you to scroll slower.ģ. 3ppf is your sweet spot. For UHD or 4k, aim for 5-7ppf.Ģ. 4 is already pushing it, and 2ppf is very very slow. At HD and 2k, you should always aim for 3 pixels per frame (ppf). With everything mathematically perfect, every tiny imperfection shows up in stark relief.ġ. Scrolling titles contain none of those small, organic imperfections that are inherent to natural human motion and photographic capture. But until Ang Lee has his way, we are stuck with this relatively low frame rate. What looks nice for a cinematic scene is not necessarily ideal for typography in motion. “Persistence of Vision” is a relative thing. Doug Trumbull discovered the same problem when creating star fields for 2001. Absent any motion blur-which we do not recommend-this can cause your eye to see each letter two or three at a time. This is as high-contrast as it gets, creating an after-image on your retina. Several factors are things are conspiring against us here: But at real time playback it seems to be bouncing along instead of flowing smoothly. Stepping through the video frame-by-frame, everything looks fine.
They won’t love you (or me) for saying this. But it will make your movie look better. But if that ship has sailed, you can still request that your post team insert a smooth, DCI-compliant, square-pixel render into your DCP authoring timelines.
We’ve even seen theaters that run everything through a scaler in the projection booth. So if you’re not resizing in the timeline itself, it’s still possible that your titles are being scaled in the signal path to the display. Which, as a reminder, is going to look like this:ĭid we mention how we feel about “1152p”?Įven if your post team swears up and down that that your titles are not being resized, be cautious: HD monitors and 2k D-Cinema projectors still have a maximum vertical resolution of 1080 lines. And here’s why: if your end titles were originally moving at 3 pixels per frame, the “1152p” workflow is guaranteeing a scroll speed of 2.8125 pixels per frame in all of your masters.
For example, we’ve previously written about 2048×1152 being a bad idea. Resizing happens when your DI workflow is based off a non-standard raster. 95% of our reports of “omg, jitter” come down to this.
That shifting pattern usually has a phase-it repeats itself every n number of frames. That’s what makes your end titles jitter. Changing those grey pixels frame-to-frame results in temporal aliasing. Sub-pixel motion is accomplished by subtly shifting the pattern of grey (actually, semi-transparent) pixels at the edges of each glyph. This means that the number of pixels your credits travel each frame is not a round integer like 3.00, but a decimal like 3.18752. Subpixel motion -> temporal aliasing -> jitter What causes it?