Resource Zone
Blog
Demo Room
Posted by Jennifer on November 6th, 2009 | 
Why Buy a Projector without a Lens?
Have you been searching for projectors and asked, “Why would they sell a projector without a lens?” You are not alone. So, we thought we’d take a few minutes and explain who buys a projector without a lens, and why it’s actually sometimes necessary.
When Would I Need a Projector with a Separate Lens?
Most of the projectors we sell include a lens, because most people are using a projector in a standard size room. But churches, classrooms, and other large venue spaces run into a problem with a standard lens projector. This is because in tehir space, they might need to mount their projector from over 20 feet back for their screen. Why do you need a special lens at over 20 feet? Consider this technological analogy.
Let’s pretend for a moment that a projector is nothing more than a fancy flashlight – at least in the sense that it follows the rules of physics. If you can, visualize yourself holding flashlight and shining it directly on the wall in front of you. When you are close to the wall, the light you see is bright, and small. As you walk backwards (walking slowly and carefully to avoid injury), the light on the wall in front of you begins to increase in size, and decrease in brightness. That’s pretty much what’s happening when you try and mount a projector (with a standard lens) back more than 20 feet (or so) back from your screen.
Now if your flashlight had a lens on the front of it, instead of plain old glass or plastic, you could dial that light in. You could ‘focus’ the light into a brighter beam, and into the size and shape you need. So, if you have to mount your projector in the back of your room, let’s say from as far back as 100 feet from your screen, you will have to have the right lens to create the image size you want, with adequate brightness.
But Why Are There so Many Lens Options?
Projectors mounting location, obviously, will vary from room-to-room, based on the unique space. And a projector’s lens can only focus the light within a specific range (say 4-25 feet). Depending on the screen size you may only get 2-5 ft of play within the 4-25ft. The flexibility depends on two factors; throw distance and screen size. When you see a specification that says it has a throw range of 4-25ft it doesn’t mean you can do any size screen from that distance, but only the specified screen sizes.
So, from a manufacturers point of view, it makes sense to offer multiple lenses on one chassis rather than sort of ‘pre-building’ several hundreds or thousands of projectors with the lenses permanently fixed to the chassis. Also, different lenses sometimes have varying costs associated with them, so providing the flexibility of multiple lenses is a cost saver in terms of production – less waste and a more agile product line. For the buyer, it can also mean the difference between having to purchase an entirely new projector, versus just a new lens, if the projector has to be re-mounted in the same space.
However, looking at the available selection of projectors in this category can be overwhelming. Take, for example, the NEC NP4100 and NEC NP4100W series product line. In it there are optional lenses that enable the user to find the right lens to cover projection distances between 2.6 – 283 feet. There are a whopping twelve different projectors that appear to be almost exactly the same. But, in reality there are two primary differences, the resolution (widescreen or 4:3) and the lens. You’d simply pick the model with the resolution you want, and the throw distance you need. Below is a chart with the throw distance for each model in the NEC NP4100 and NP4100W lineup.
| NEC NP4100 Series (4:3) | |
|---|---|
| Model | Throw Distance |
| NEC NP4100 | ships with no lens |
| NP4100-06FL | 2.6 – 10.6 ft. |
| NEC NP4100-07ZL | 3.5 – 60.9 ft. |
| NEC NP4100-08ZL | 4.7 – 79.9 ft. |
| NEC NP4100-09ZL | 5.8 – 152.3 ft. |
| NEC NP4100-10ZL | 11.6 – 283.3 ft. |
| [ Quick Specs : XGA (1024 x 768) resolution, 6200 lumens, 2100:1 contrast, 38.6 lbs. ] | |
| NEC NP4100W Series (16:9) | |
|---|---|
| Model | Throw Distance |
| NEC NP4100W | ships with no lens |
| NP4100W-06FL | 2.6 – 10.6 ft. |
| NEC NP4100W-07ZL | 3.5 – 60.9 ft. |
| NEC NP4100W-08ZL | 4.7 – 79.9 ft. |
| NEC NP4100W-09ZL | 5.8 – 152.3 ft. |
| NEC NP4100W-10ZL | 11.6 – 283.3 ft. |
| [ Quick Specs: WXGA (1280 x 800) resolution, 5500 lumens, 2100:1 contrast, 38.6 lbs. ] | |
As you can see, NEC gives you alternatives for up to 283 feet of throw distance in this product line. And, the low end of the throw ratio doesn’t change nearly as much as the high end of the distance covered.
Quick Tip : Optimally, you will want to select a lens that fits you squarely in between your distance requirements. So, if you are planning to mount your projector 150 feet back from the screen, you’d do better to choose the “10ZL” model than the “09ZL.” This is because there is slightly more distortion when the light passes through the edge of the lens. A projector has what’s called a “sweet spot” for the distance that provides the optimum image quality through the lens, and that spot is near the mid range of the recommended throw distance. Call a Projector Expert for more information on that.
Why can’t you just use a zoom lens?
Unfortunately, zoom lenses don’t have that much flexibility. Generally speaking, a zoom lens can give you an extra 2-5 feet of “play” in the projector’s throw distance. So, while the extra 2-5 feet is nice, it won’t help you if you need an extra 100 feet. This may change in the future, but for now, the zoom lens is mostly a tool to help the home user install their projector with a little less accurate math.
Quick Tip : The general rule of thumb for throw distance is that your projector creates one foot of image for every two feet back from the screen. So, at 50 feet back with a standard lens, you would have approximately a 100 foot width, and a very dim image.
What if I Need to Mount a Projector Very Close to my Screen?
If you want to set up your projector within six feet of your screen, and you want a large image, you’ll want to find a projector with a “short throw lens.” We have a quick tutorial about those here. You can also call a Projector Expert and find out if a “lensless” projector would be right for you. In some cases, they offer the best solution, but there are only a few made.
How Much Will a Projector and Lens Cost Me?
Lenses are typically around $1500-$2000. It’s usually easier to buy the manufacturers lens, for compatibility and inventory reasons. There are some other lens makers out there in a pinch, but prices are usually about the same for a business projector lens.
Projectors that accept multiple lens options are usually in the large installation category. They are high brightness, and higher resolution units, so they start at around $2000 and go up from there. So your lowest priced scenario would be around $3500-$4000 and the prices go up from there. You’ll pay a little more for brightness and features like network monitoring, filter free design, 24/7 useage, lens shift, and other good stuff.
Our NEC series featured here is a premium line, and it retails for around $7,000. But call a Projector Expert, or get a Quick Quote for a significant discount.
Quick Tip : Keep your eye out for installation projectors that sell without a lens. A lower price is usually a tip off. There are some high brightness units that look like a great deal, but that actually will need a lens to work. The NEC lineup we feature here does have one base unit featured, but the rest of the line up ships complete.
Well that’s about all we have for now. Please call a Projector Expert if you have any more questions about any of your large venue projection needs!
Related Posts
Share and Enjoy:
Loading ...