Posted on July 9, 2018 By Art Feierman
BenQ TK800 4K UHD Home Entertainment Projector Review – Hardware: Overview, Inputs and Connectors, The Lens
As always, let’s start with a quick tour of the projector, then we’ll get into some more detail. From the front, you’ll notice that the recessed, 1.2:1 manual zoom lens, is offset to the side (to the right, if facing the projector). Further to the right is the front IR sensor for BenQ’s remote control. Venting of hot air is on the left side of the front.
This is a relatively small projector, so if you have it on a table, you probably won’t want to be sitting a foot or two forward of the projector and just to the right of it, or you will get very slowly cooked with warm air shooting from the vent.
Down below the front is a drop-down foot, with the button to release the foot directly above – not quite on the front, not quite on the bottom. That takes care of the front.
Now we’ll move to the top, right behind where the lens is. That where you’ll find two lens controls – focus and zoom – to adjust. These controls are also recessed. The control panel is also on the top, as is the door to replace a lamp. All the inputs and connectors are to be found on the back of the HT2550.
No real surprises here, the HT2550 is pretty well endowed for a lower cost projector. True, like most home projectors today, there are no more “legacy” composite video or S-Video connectors. What there is, from left to right:
A pair of stereo audio jacks – one in, one out. A PC VGA input (standard DB15 connector) comes next. It can handle analog computer, or component video.
A pair of HDMIs is next. They are different! The left one is HDMI 1, and is HDMI 2.0 with HDCP 2.2 – which meets the requirements of Blu-ray UHD and other copy protected content.
The second one is the good old HDMI 1.4 which has been around for a number of years. In theory, the first one should handle anything HDMI, but most manufacturers include an HDMI 1.4 – just in case there’s a problem, perhaps with a 10 year old player…
As always, I must complain – a third HDMI input would be very helpful for those not doing switching through an AV receiver. I tell all the manufacturers, but few have done so. Most recently a Vivitek had three. Other than high end commercial projectors, though. two is all you will normally find.
Next comes a USB Type B, for servicing, followed by an old school, RS-232 serial port, for command and control of the projector. Then comes the USB Type A port which is there to provide a 5V 1.5amp output. (It can be used for recharging most 3D glasses). Finally there’s a 12 volt screen trigger. That’s something not often found on lower cost home projectors, but, if you need it, great. It’s used for raising and lowering a motorized screen which has a 12 volt trigger. More and more, these days, however, companies are moving to wireless control rather than 12 volt triggers.
As stated previously, the HT2550 has a very modest zoom lens – 1.2:1. Other projectors in the $1,000 to $2,000 price range may have as little as 1.1:1, or as much as 2.1:1. As there is also no lens shift, count this BenQ projector as one with little placement flexibility. Still, those of you mounting the projector should find enough zoom range to let you place the projector and mount at a workable distance to fill the screen properly.
Without lens shift, however, you really want to have the projector mounted, or on a table, at the correct height, so as not to have to use keystone correction, which degrades the image sharpness slightly. Think this way, why spend for 4K UHD, if you use a feature that probably reduces sharpness down to that of a 1080p projector not using keystone correction.
If you focus the projector looking at the dead center, edge sharpness is pretty good, no – let’s call that very good for a projector in this price range especially one where a chunk of the price is dedicated to having 4K UHD resolution. Well, one advantage to a lens with very little zoom is that it’s a lot harder to find “very sharp” in a zoom lens that has a lot of zoom range.
Other than the Kensington lock slot near the bottom right (for security), there’s only the power receptacle. That’s all folks!
Here’s a lens throw chart for using the HT2550 with a 100” 16:9 screen. And, also, the lens offset, which tells you how far above or below the screen surface the projector lens should be. If you are getting a larger screen, or smaller one, you can calculate the numbers you need, in a few seconds. Example:
Lens Throw Chart for 100,” 16:9 Screen
If you are going with a 125” diagonal screen and want the closest placement of the projector to the screen, then multiply the 10 feet 8 inches (128”) by 1.25, since your larger screen is 25% larger. That’s 160 inches, which is 13.8 feet, for the closest placement.
Lens offset is almost 5 inches (125mm). Translated, if you put this BenQ on a table top pointing at a 100” screen, the center of the lens should be 5” below the bottom of the screen surface (or, if ceiling mounted, 5” above the top of the screen surface).
That’s a very reasonable amount of lens offset.
And, if you went with a larger screen, say a 120″ diagonal (20% larger) l, then the offset would be 20% more than the 5 inches, which works out to six inches.
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