Logitech HD Pro Webcam C910 can not focus to infinity

They promise a lot for this camera: Full HD recording in 1080p, brilliant pictures with 10 MP resolution (2592x1944), Carl Zeiss optics, autofocus for 7cm and beyond …

So I got this camera at a local shop and fired up guvcview. The camera produced a picture right away. An that’s about the end of the success story.

After some unsuccessful attempts to focus on the building on the other side of the street I closed guvcview and started a Google search. It turned up the following message by kpeppard, “Support Specialist”:

Also, our webcams are only made to go to a maximum 6 feet then it starts to get blurry.

HD Pro Webcam C910 Focus Issue (MacOS) - Logitech Forums

In fact the camera can focus down to a distance of about 4cm (better than they promise). But when the focus is set to the best possible “infinity” the image is in focus at a distance of 40cm. Anything further away gets blurry.

I made all my experiments with the best possible resolution using fswebcam

fswebcam -d /dev/video0 -i 0 -r 2592x1944 -p YUYV logitech.jpg

and guvcview in video mode @1920x1080.

Warning: Don’t buy this unuseable piece of CHARLIE-ROMEO-ALPHA-PAPA.

Just wondering: being short-sighted I wear glasses for distant vision.

Instead of throwing this cam against the wall, I could fix a negative lens with a focal length of 400mm in front of it. That should fix the issue at the cost of some chromatic aberration?

vodoo wrote:
> Just wondering: being short-sighted I wear glasses for distant vision.
>
> Instead of throwing this cam against the wall, I could fix a negative
> lens with a focal length of 400mm in front of it. That should fix the
> issue at the cost of some chromatic aberration?

Yes. If there’s any gap between the camera lens and the new lens, the
focal length will be slightly different. There’s a simple formula which
I’m sure is on the interweb somewhere. And you can minimise all types of
aberration by using a better lens - perhaps an old spectacle lens from
your optician?

I have this webcam.

I use it for inside my computer room, and for that purpose, it is superb.

Without a qualification, IMHO that is nonsense.

My recommendation, for people who want a superb HD webcam for recording inside a typical room is the EXACT OPPOSITE of what you noted. This is a superb webcam. It is HIGHLY recommended for that purpose.

But if you want a webcam that will record buildings across the street at HD resolution, then IMHO one needs to research this a bit more before purchasing.

@oldcpu

I knew that you have this cam. Your argument is basically “I do not use it beyond its limited focus range”. But I think it is legitimate to use a webcam with superb specifications for more than just recording faces in front of the screen. It makes me angry to see that they advertise full HD and even still pictures at a resolution of 2592x1944 but the customer can’t even use the camera at a distance of 2 meters without getting blurred pictures. They do a lot of software sharpening to make it look better, but the actual resolution beyond any distance of 1 meter is miserable and does not correspond to the resolution this hardware would be capable of.

If you don’t care to get what you paid for and what has been advertised you may be a happy customer. I am different. I feel a bit like when I would have bought a car (take any expensive German brand name) to find out later on that its range was limited on purpose to drive a 10km trip distance at the maximum.

The most I have operated it is at 3 meters (longer than the 2 meters you mentioned), and it was focused nicely there.

I typically have no need for more than 1.5 meters, and if I had that need, I definitely would have researched this a lot more BEFORE purchase. I checked a NUMBER of online images with this webcam BEFORE purchase, looking for representative images (to what my planned use was). I do want a webcam that can focus close up images at HD (for illustrating items held up to the webcam).

From what I recall, there are many cases in the internet of webcams that do not focus properly to infinity, and so if I were to spend a lot of money on a more expensive webcam for looking at items very far away, for certain BEFORE I laid my money down I would check out that aspect IN DETAIL.

You can’t be refering to me here. I went in with eyes open. I got what was advertised. No where do I recall seeing anything referring to this being a superb webcam for distant images on the horizon, nor for it being a superb webcam for surveying items across the street. Never do I recall seeing that advertised. IMHO you inferred something that was not advertised. At least if it was advertised, I NEVER saw such an advert. JUST because a webcam is HD does not mean it will focus perfectly to infinitely.

This webcam does what I want. It does what I saw it advertised to do. And it does that and more. Its very nice.

While I can clearly see your frustration, I can only comment that what has happened here is a classic case of not researching all details before purchasing.

Wrt your comparision, ! … lol … when you find an expensive brand name German automobile for the same price as your webcam, please let me know the location of the car sales lot ! :slight_smile:

As an experiment I fixed a simple concave/convex lens (f=-400mm) in front of the short sighted C910 webcam. This is the result with identical focus settings, 1280x720 resolution and 4x zoom without and with the auxiliary lens:

http://www.lawbiz.ch/pastebin/testpic-1.jpg http://www.lawbiz.ch/pastebin/testpic-2.jpg

Can anyone see a difference?

How to fix the Logitech C910 Webcam for distant vision

Order a corrective eyeglass lens from your optician and ask him to cut the lens to a diameter of 30 mm centered on the optical axis. This lens should have -2.5 diopters or a focal length of -400 mm. A plastic lens with standard refractive index will do. The “better” lenses with a higher refractive index are actually worse for our purpose, because they cause more chromatic aberration.

Paint the front of the webcam black, covering any white printed markings and the LED’s. A webcam designed for indoor use will sometimes look out of the window, and we do not want to have any reflections, especially at night. Cold ceramic paint, which is used to paint on glass, is suitable for this purpose.

Now the lens is centered over the webcam, the concave side towards the camera. Some precision is essential here, to make the optical axis of the corrective lens coincide with the camera lens. Fix it with two tiny droplets of liquid glue applied at opposite sides of the lens close to the edge of the webcam. Some mounting medium used in microscopy like Eukitt is best for this. Do not use cyanoacrylate glue. It will make your lens unusable. Now your webcam looks like this:

http://www.lawbiz.ch/pastebin/C910.jpg

It will produce sharp images without any noticeable optical defects.

The corrective lens cost me CHF 76.00 plus CHF 20.00 for the cutting (about 80 Euros). The resulting webcam is much cheaper than a “real” cam with comparable capabilities and performs well on any distance from infinity down to about 5 cm. For best results reduce software sharpening (“Sharpness”) to 216. The default of 224 is way too much.

Thanks so much for the tip on using the negative lens - we had some old glasses (about -2.75 i think) and i stuck (“bluetac”) a lens to the front of the c910 and it now sees clearly now when used to monitor my home remotely. I love it!

I picked up a -2 diopter corrective lens for a sony camera (FDA-ECN20) on Amazon for $5. Worked like a charm.

Hi - I bought the C920 version of this webcam and it has a similar issue.

I love your optical corrections :slight_smile: I tried a set of my old glasses, but didn’t really like the look!

I saw that some people have taken them apart and adjusted the focus.
Logitech C910 and C920 IR (Infrared) conversion for nightvision | ALCS

It works, but I’ve realized that the limited focus range was probably an optimization by the Logitech engineers:
1/ In low light the firmware puts the lens to the far-point, and it is far more likely that you want the camera focused at about 60cm than 2m→∞
2/ The constant lens autofocus adjustments makes less noise when the lens is set at the far point (as it will be almost all the time)

However, I’m happy with my adjustment. If anyone here has the C920 and would like to see how to take it apart I put a video here:
Taking Apart a Logitech C920 Webcam and Adjusting the Far-Point Focus Limit - YouTube

I wonder if the new C930e will have the same issue? It has even wider field of view, so the edge focus will be even more of an issue, but maybe they considered people using it to show a whole room of people doing video conferencing, not just one person sat at a desk?

Neat thread! (Had never noticed this one before)