DL2 vs. DL1

Todd,

I'm not exactly sure what "tolerances" you are looking for an explanation about, so I'll hit all the similarities and differences.

Physically, there is only one main difference between the DL.2 and DL.1 (other than the obvious top box) and that is the pan bearing. The DL.2 has a much more robust pan bearing on it allowing for side hung applications (although we don't recommend this because it causes issues with lamp life and cooling correctly). If your DL.1s are going to be hung box up or sitting box down, this is a moot point.

Operationally the big difference is the encoders. The DL.1s use analog style encoders while the DL.2s use much higher resolution digital encoders. The exact resolution numbers escape me at the moment, but 1000 times higher for the DL.2 is a completely reasonable guess.

This is not to say that the movement accuracy and repeatability on the DL.1s is bad, only that the DL.2s are better.

Other than that, everything is the same. They both have the same projector, same cooling/filtration system, same yoke, bezels, etc.

Matt,
You addressed the exact things I would want to know, thanks. Of course, I am concerned about a few things.

[quote=schiefels]
...DL.2 has a much more robust pan bearing...


As an eventual point of failure, I would anticipate a need to replace pan bearings when movement and indexing showed inconsistencies that were no longer within the user's acceptable tolerance.
Albeit replacing a bearing every couple or years is perhaps reasonable. I still remember the headaches of changing pan belts on Spot 250s simply because it was tedious.

[quote=schiefels]
...Operationally the big difference is the encoders...
...DL.1s use analogue...
...DL.2s use much higher resolution digital encoders...


Knowing how analogue encoders work, I know that their long-term ability to index to the same location is weak. In the application I am using, Pan will be the most critical indexing function simply because all of the installations are to use complex edge blending where the projection surface is close enough to the audiences where they will be sensitive to deviations.

[quote=schiefels]
This is not to say that the movement accuracy and repeatability on the DL.1s is bad, only that the DL.2s are better.


Yes, just from what you pointed out, the DL.2 would be better but only in a side by side comparison could we know how significant.

Just a thought...
I did a few calculations to evaluate possible tolerance.
At 45.9' of Throw, at a wide Zoom, the DLs have a projection width of 25.3'.
This is a beam angle of 15.4 degrees (arctan [(25.3/2)/45.9)] = 15.4).
Since the projection is 1024 pixels wide, this would yield an angle of 0.0150 degrees per pixel.
Of course since most of the Axon stock clips are DV NTSC, it means we're dealing with 720 x 480. Let's pretend that in scaling the image, the media server doesn't recognize anamorphic pixels and therefore we're talking about an image 640 x 480.
At a projection of 640 wide, this would yield and angle of 0.0241 degrees per pixel.

Pan is a 16 bit configuration, it means that at highest possible resolution, the DL.2 would have would be 65,536 steps. Since the Pan range is 400 degrees, this means that there are 163.84 possible steps per degree.
The reciprocal of that is 0.0061 which is about a forth of a pixel in accuracy using the 640 pixel or about half of a pixel accuracy at 1024.

Now if we consider the DL.1 and your guess on accuracy, we see a different outcome. We'll call the DL.1 6,600 steps which is 1 tenth that of the maximum resolution from 16 bit. Using the same equations, here are my results:
A 640 Pixel accuracy is about three pixels.
A 1024 Pixel accuracy is about four pixels.

On a specific application, I have throw distance widths of 13' 4".
Roughly translating, that means each 1024 pixel is about 1/8" So it means I'll have a possible slop of indexing equal to about 1/2 an inch.
My audience is sitting about 10' to 30' from the screen. So as you can imagine, this is noticeable, like reading 1/2" wide letter text from 10' to 30' and most people can easily do that without glasses.

It may be a mute point but I am hoping to demonstrate in my calculations that the possible difference between a DL.1 and a DL.2 is significant for those of us who intend to edge blend.

Here are my questions...
Can I order my DL.1s with the same digital encoders and pan bearings that come on a DL.2?
Or Can I order DL.2s without the Media Server at a reasonably proportionate cost to the DL.1?

I am eager to get feedback. Oh, and check my calculations. I've been know to make mistakes when crunching numbers off the top of my head.

Todd,

If my first post I had a major brain fart, so let me come at this at a different angle.

Positional precision is not really dependant on the encoding system of the fixture. The encoders are there mainly for detection and correction of positional error. When a new DMX value comes in for a movement (pan or tilt) the movement distance is calculated in motor steps, and the motors move this set distance. The encoders only come on after the movement has occured to verify that the correct amount of distance was traveled. So, as long as the motors do not misstep (which really only occurs by a physical force acted upon the head of the fixture), the encoders don't come into play.

Having said that, something I should have mentioned before (please excuse the brain fart) is that the motion drive ratios on the two fixtures are different. The DL.1 has a 6:1 drive ration while the DL.2 has a 10:1. Given this fact, the DL.2 movement is more precise because we have a finer control of the head.

One thing to keep in mind is that the DL.1 was conceived and designed before the Collage was, and so it wasn't really designed for that purpose. I have done some limited testing here in the office with Axons and DL.1s for Collaging, in which everything worked quite well, but this was only at a throw distance of ~12 feet.

[quote=SourceChild]As an eventual point of failure, I would anticipate a need to replace pan bearings when movement and indexing showed inconsistencies that were no longer within the user's acceptable tolerance.
Albeit replacing a bearing every couple or years is perhaps reasonable. I still remember the headaches of changing pan belts on Spot 250s simply because it was tedious.
I don't think these should be considered points of failure. When I mentioned that the DL.2 pan bearing was more robust, this statement was aimed more at torsional rigidity. Hanging a unit sideways puts an enormous amount of stress on a bearing in a way that is doesn't like. With the fixture sitting box down or hung box up, the stress on the bearing is well within tolerances and these should not fail.

[quote=SourceChild] Here are my questions... [quote=SourceChild] Can I order my DL.1s with the same digital encoders and pan bearings that come on a DL.2?
No, you can't, but given the above information, this is pretty moot.

[quote=SourceChild]Or Can I order DL.2s without the Media Server at a reasonably proportionate cost to the DL.1?
Again, no.

If FOH preview is absolutely required, one option is DL.2s in the rig (for the motion precisioin) and Axons at FOH for preview. Patched correctly, the Axon's will display the exact same thing as the DL.2s in the rig. Splitting video signals from the Axons or hacking into the DL.2s (besides voiding the warranties) gives more points of failure and may lead to more problems than it solves.

Todd,
i don't want to sound odd here but if i was going to spend the amount of money your talking about i would have this entire post offline.
Of course it makes no difference whatsoever to me just a comment that's all.
This forum is a fantastic resource but sometimes a short phone call is good too but maybe you don't want to use a phone.

Cheers C

[quote=cormacjack]
...would have this entire post offline...
...forum is a fantastic resource but sometimes a short phone call is good too....


Good Point!
You're right and for any details beyond this I would call.

I can't help but think I'm not the only one who has these questions or concerns. Under the circumstances though, I was interested in encouraging community feedback.

Especially because (as Matt pointed out) I could always put DL.2s in the air and an Axon in the rack at FOH. Of course this is basically saying "The DL.2 preview monitor option at the bargain price of $8,000 more per light." This is just a little bit obscene to me.

Todd,

What I don't get is why for this particular installation having full preview of everything without using the projectors is such an issue?

There are many things you can't do with preview. One is positioning of the units, obviously Collage alignment. Not to mention seeing what it actually looks like on the projection surface you are using. It is kind of like saying I want to completely pre-program my rig for a show using pre-viz and never seeing what it will actually look like on stage before the show because I don't want to strike the lamps.

If you need some type of preview you could just always use a single Axon for doing to preview programming. You don't need one for each unit. That is just overcomplicating things.

[quote=SBlair]
What I don't get is why for this particular installation having full preview of everything without using the projectors is such an issue?


Scott, It's complex to explain but it all comes down to lamp life, electricicty consumption, and resource availability. The first DL.2 project is Shoreline so I'll use that as an example.

For the three 10,000 projectors I put in Shoreline two years ago, running for 15 to 20 hours per week during the programming time, I would have to replace lamps twice as often. This means an additional $6,000 per year for lamps. Add in electricity cost, air conditioning, and other costs. All in all, using the preview monitors, I have a cost savings of close to $10,000 per year.

Now applying this to the DL.2s I would be installing in the new childrens center, I have speculated a cost savings of as much as $10,000 per year also.


Hey Scott, if you want a convincing arguement, how many rental companies would buy more DL.2s if they know they can turn off the projector, leave the light in the road case, and use it as an additional media server...?

Todd,

I think your numbers for the lamp cost might be off by about an order of magnitude for what you estimate the additional costs would be for the DL.2 lamp usage. How did you calculate this?

Most rental companies don't want to spend the money for a DL.2 to only use it as an Axon. The Axon has proved to be a very affordable solution for people wanting to pre-program.

I would suggest just getting one Axon that would allow you to do a lot of the pre-programming. I think you'll still find that you're firing up the fixtures a lot anyway as there are many things you just can't see otherwise.

"You're right and for any details beyond this I would call.

I can't help but think I'm not the only one who has these questions or concerns. Under the circumstances though, I was interested in encouraging community feedback."


I found this thread fascinating. thank you for your willingness to air your thought process.

peace, Tim O