paulrph1 Loc: Washington, Utah

Makes not sense. Buy a extension tube the would be cheaper and more functional.

Boentgru Loc: Boston, Massachusetts, USA

Read the post; he is looking for protection of the sensor from dust when changing lenses. Really, a neutral (no magnification, no color, 100% transmission, no shift) optically transparent cover.

jerryc41 Loc: Catskill Mts of NY

Theoretically, yes. In the real world, no. If it were that simple, the manufacturers would be doing something like that.

Boentgru Loc: Boston, Massachusetts, USA

The problem is, if one adds another surface to protect the sensor, that surface now collects the dust/dirt and it is also in the optical path. So it must be actively cleaned. Maybe that's easier than cleaning the sensor, but it adds more effort, complexity and cost to the operation of changing lenses.

lamiaceae Loc: San Luis Obispo County, CA

No, sorry.

I'll leave this for imagemeister since the OP unfortunately does not actually understand what 1.4x, 1x or 2x means. And beyond that the OP does totally have me lost. Super Glue the lens on perhaps? LOL Has the UHH gone Onion?

OldEarl Loc: Northeast Kansas

The magnification of a tele converter is the square of the number. 1.4x would give you roughly twice the magnification the lens already gives. A 2x would give you four times the magnification. A 3x gives mine times the magnification. In addition to the magnification of the image they also magnify the effects of any flaw in the lens, dust between elements and grease (lanolin) of your "protective" filter.

Ergo, if I set uo a 3x converter on a 105mm lens it will give roughly the same magnification as using a 300mm lens with no converter, but the image with the converter will probably reflect all the other variables (unless. of course. the 300 is a Kalimar you picked up for $25 at dog sale).

The question of a 1x converter (if such existed), it is a little worse than a clear filter in that it would be ground and its flaws would be noticible.

wdross Loc: Castle Rock, Colorado

In other words, you want to "seal" the front body opening. Although is would prevent your sensor from getting dirty, it would also affect your image quality. It would be a piece of glass that was not accounted for in the lense formulation. It would be easier to just get a camera with the ultrasonic sensor cleaner and just take care when changing lenses.

amfoto1 Loc: San Jose, Calif. USA

As I understand it, you want a "plain 1.0X teleconverter" (which would have to be called something else because it no longer adds to the tele nature of a lens, nor does it convert anything) merely to "seal" and protect the sensor...

No such thing exists for a modern DSLR. Nor should it because it would be a bad idea for two reasons:

1. Adding optics in that manner would reduce the image quality potential of every lens you use. You simply cannot add more glass without some optical "cost".

2. The sensor is already sealed and protected. Every DSLR made has some form of filter in front of the sensor. When you "clean the sensor", you aren't actually cleaning the sensor itself. You are cleaning a filter that sits in front of it. Most DSLR sensors have an anti-alias filter, designed to slightly blur the image to reduce chance of an optical effect called "moiré". All have some sort of coatings on the filter, too... to reduce reflections and, in many cases now, to resist dust adhering to the filter.

When you mention magnification, some responders are immediately thinking of macro extension tubes, which have no optics inside and are merely a spacer that moves the lens farther from the sensor plane so that it will focus closer (i.e., give higher magnification), but at the cost of no longer being able to focus to infinity while the macro extension tube is in place.

I would simply suggest you learn to clean your camera's sensor (okay, okay... actually you'll be cleaning the filter in front of the sensor). It needs to be done carefully, but it's not rocket science. There is comprehensive info about cleaning sensors available at http://www.cleaningdigitalcameras.com/

Alternatively, have the sensor professionally cleaned periodically. It's not very expensive to have done and most of the time other camera service and cleaning is performed at the same time.

If it really, really bugs you... buy a fixed lens camera. Get a point-n-shoot with a non-interchangeable zoom lens. If the range of the zoom lens isn't wide enough for your purposes or it doesn't focus close enough for macro shots, you can get auxiliary lenses that attach to the front of the camera's lens to make it's angle of view wider or more telephoto or closer focusing.

Incidentally, when using a "real" teleconvter (which can be found in 1.4X, 1.7X, 2X and 3X strengths most commonly), the lens' closest focus distance doesn't change at all, but it's magnification does change by the TC's multiplier. For example, if a lens focuses to 18" and produces 0.21X magnification at that distance (about 1/5 life size), if you add a 1.4X teleconvter to it will still focus to 18", but now will render about 0.294X magnification (a little less than 1/3 life size).

Conversely, a macro extension tube without any optics does not change the lens' focal length, but does change it's closest focusing ability, and the degree of magnification along with it.

The idea of some sort of "lens base" with interchangeable "lens heads" isn't a new one, by any means. In my camera collection I have a lovely Zeiss Ikon Contaflex Super B from 1963 that's designed exactly this way. Instead of the entire lens being removed and replaced to change focal lengths, part of the lens assembly remains attached to the camera all the time and five different interchangeable "lens heads" are available to provide different focal lengths (35mm, 50mm, 85mm and 135mm) and 1:1 macro. (http://camarasclassicas.blogspot.com/2011/02/contaflex-super-bc.html)

In the late 1950s and early 1960s there were a number of camera manufacturers offering SLRs similar to this, mostly done to keep costs more reasonable. The problem is that it seriously limits the range of focal lengths that can be offered. One advantage of this type of design was that it allowed for an in-lens leaf shutter (instead of the focal plane curtain or blade type shutter most SLRs use). Unlike other types of shutters, leaf shutters allow flash sync at all shutter speeds. But they have limited top speed. Most are 1/500 tops... a very few get to 1/1000 (compare to modern focal plane blade-type shutters that can do 1/4000, 1/8000 and in a few cases even faster speeds).

Leica even went so far as to offer a series of APO-Telyt R super telephoto focal length "lens heads" for use on different "focus modules", to provide 280, 400, 560 and 800mm lenses. (http://www.apotelyt.com/photo-lens/leica-apo-telyt-r-module) But these didn't do what you want either... The focus modules mounted to the camera via bayonet, to be able to swap out and use other R-mount lenses on the camera.

lamiaceae Loc: San Luis Obispo County, CA

I'm pretty sure it is the light transmission or numbers of stops that falls off as an inverse square. At least the ones I've seen and used are like that. Virtually every "force" or "energy" in nature follows an inverse square rule. Note other repliers quotes of focal length differences as well. Say 400mm to 560mm with a 1.4x. But yes, an f/4 would then be f/5.6 or one stop. A 2x two stops (1/4 the light), a 3x three stops (1/8 the light). I have two older models that have conversion calculators built on. I'm pretty good with math. But this stuff confuses a lot of people, even professional photographers. See photo below.

(Download)

lamiaceae Loc: San Luis Obispo County, CA

To add to the Tele-Converter discussion. Not the second half of the question.

There may be 1.2x CT's, but 1x would make no change in magnification Lx1=L.

Say 400mm to 560mm with a 1.4x. But yes, at f/4 would then be f/5.6 or one stop less light. A 2x two stops (1/4 the light), a 3x three stops (1/8 the light). I have two older 2x & 3x models that have conversion calculators built on. This stuff confuses a lot of people, even professional photographers. See photo below.

3x power - 1/8 the light; 2x power 1/4 the light

(Download)

paulrph1 Loc: Washington, Utah

I did read the post. But the solution he mentions brings in magnification which is not a valid solution. BTW there is no valid solution to his problem other than to get the censor cleaned. Adding another layer of confusion is not a solution but careful handling of the camera is.
Oops, there is another solution but a bad one in my estimation and that is buy a point n' shoot camera.

carl hervol Loc: jacksonville florida

no make no sense''' mount your lens with the body facing down and don't leave the lens off the camera or the body cap never point your camera up with out something on it .I never had to clean a senor in over 9 year .Use common sense it your best answer.

CO

The OP does understand that. The reason for wanting a 1x converter was to be able to leave the converter mounted on the camera as a dust barrier.

bruswen Loc: Eugene OR

The most common solution used by photographers to avoid changing lenses in harsh conditions is to buy a second (or third) camera body, plan ahead, and have other needed lenses mounted on those bodies. That way, the cameras are all ready to go, there is no risk to the insides of the camera, and you don't miss a shot while swapping lenses. The price of an entry level camera body is comparable to what you would pay for a teleconverter.

paulrph1 Loc: Washington, Utah

I just received an ad. from Adorama about a new Canon camera that has a fixed lens but does not appear to be a point n' shoot camera either. If he wants to spend the bucks that would be the ideal solution. No dirt into the camera every. Maybe not a DSLR but a Leica with a zoom.