Is your camera image sensor dirty, and if so, how do you clean it?

Do you have dust and foreign particles on your camera’s image sensor?  If you have an interchangeable lens camera body, you probably do. But in many cases, a few random specks of dust won’t be detectable in normal photography.

However, if you have visible spots showing up in your images, you know it’s time to clean your camera image sensor. For example, in this closeup of the N2A Goodyear Blimp, if you look closely at the end of the black hand drawn arrows, you can see the results of dust on the image sensor of my second-hand A6300 camera. [Obviously, all dust is the fault of the first owner, and I can keep claiming that until after I clean it.]

Photo of the goodyear blimp, with small dust spots evident in the photo.

Now that you know there are at least a few pieces of dust/debris on your image sensor, you can characterize just how bad the problem is by shooting a “flat” image.  Point your camera towards a clear patch of sky, put the lens in manual focus mode and defocus it, and take a photo that is just slightly over exposed. [Note that to take a true astrophotography flat you need to do more than this, but for the photos below I didn’t bother. You risk having cloud shapes show up in your flat image by not having a tight white cloth over the lens….but since we are just looking for dirt it’s not critical that your flat not have gradients in it.]

defocused image showing dust and debris on the sensor

If you have a lot of debris on the sensor, it will be easily visible directly in the image. In the image above, you can see I even have some type of fiber or thread (middle right). This is an example of a sensor that definitely needs cleaning.   But you can also digitally enhance these images to highlight the debris more, which is useful in cases where the amount isn’t as bad.  Just import it into a photo editing tool, and use the “auto adjust input levels” feature to get something like this:

digitally enhanced image showing lots of debris on an imaging sensor

With digital enhancement this looks super bad, but as you can see from the image of the Goodyear Blimp above, even this level of dust and dirt doesn’t mean you can’t take a mostly usable photo with the camera.


How to clean your image sensor

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Bearing Replacement on an iOptron Cube E 8500 Alt/Az Telescope mount

I had to replace one of the Alt bearings in my Cube E mount (it was “grinding” and causing star trails at 1-5 second exposure times due to vibration).  I made a video of the procedure here:….h?v=TrKLkgV_WYM


The iOptron Cube E 8500 that I have uses 2 sizes of bearings:


1x   6804z bearing (20x32x7mm) for the Alt axle closest to the telescope.

3x  6803z bearings (17x26x5mm) for the ALT axle nearest the “lock” handscrew
and for both the top and bottom of the AZ axis in the bottom.

I purchased and used this NSK brand bearing.

You’ll also want a 14mm or 9/16th box end wrench to remove the AZ axis bolt head if you need to access the bottom.

Before/After results (click to enlarge):

Aftermarket Glowforge Hinge bracket installation

I’ve had issues with the front handle and rear hinges separating from the glass lid of two different Glowforge units.  After repairing one side of the rear hinge that was separating I decided to try out an aftermarket hinge bracket designed to get a better connection between the glass lid and the two hinges.

I paid $160 with shipping to an eBay seller for item number 175473691329 “New GLOWFORGE Aftermarket LID Hinge Repair Bracket, All Metal Construction” which has a U-shaped channel to surround the rear edge of the glass lid.  It was a bolt on (and silicon sealant glue) procedure, and the hardest part was unsticking the double sided adhesive used to hold the glowforge lid ribbon cable in place.  [I ended up using dental floss to saw through the sealant behind the cable….when I replaced it I just used electrical tape to hold the cable in place.] I also had to spend some quality time removing the epoxy that I had used to initially repair it for a few months.

The procedure went smoothly, and the lid appears to be working (and sticking) well, although only time will tell for sure how much better this bracket is compared to the original one.

Sphero 2.0 battery replacement

The original batteries in my (8-10 year old) Sphero 2.0 died.

bloating lipo lithium batteries
Once I got the sphere open and removed them, it was clear that they had “bloated”.
They are marked 702035 (7mm thick, 20mm wide, and 35mm long).  However, I don’t recommend buying 702035 batteries to replace them, as the opening they need to go into is closer to 30 or 32mm in length. If I had to do it again, I’d order these 702030 batteries instead.
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Reverse Bifocal Trick for Prescription Crafting Glasses

I need optical magnification to work on small crafting projects. However, I also wear prescription lenses, so used a headband based magnifier that I could wear with my glasses. It worked fine, but I didn’t like having to wear two different things on my head, and the forehead mount was a little uncomfortable.

So, I’ve come up with a trick that allows you to order prescription glasses that include a magnifying inset lens. For those of you who wear bifocals…yes, I’m talking about bifocals. By turning the NV (Near Vision) field of a bifocal prescription as high as you can get it, you can get a magnifying bifocal insert of 1.87 X or greater.

The formula that relates optical magnification to dipolars is:

Magnification = (Dipolar / 4) + 1

So with the maximum +3.5 dipolar Near Vision (NV) setting allowed by Zenni Optical, I’m able to get prescription glasses that include a 1.87X magnification inset.

Of course, they are down near the bottom of the field of vision, which works OK for reading in your lap, but not as great if you paint with your elbows on the table like I do.

To move the magnifying areas from the bottom of the glasses to the top, you need to rotate the lenses 180 degrees, AND you need to swap the right and left lens. [So that the bifocal inserts are on the insides, and not moved to the outside of the lens…]

This means that when you ORDER the glasses you must REVERSE or SWAP the OS and OD (Left/Right eye) prescription lines!  Other than swapping for left/right eye, the cylinder and axis numbers don’t need to be changed, as the 180 degree rotation is a perfect no-operation for them!

You also need to order a lens and frame style that is perfectly symmetrical, so that you can fit the lenses back into the frames after you rotate and swap them. I recommend metal frames held together with screws, or rimless models where the lenses bolt directly to the frame pieces. (But watch the mounting holes for symmetry!) Round lenses are usually your best bet, but you could make it work with some of the hex or octagonal lens styles.

I used Rimless Glasses 3229415 from Zenni Optical. If you use my $5 “Refer a friend” link, you get $5 off, and I get $5 towards my next non-standard experimentation with optics (because this wasn’t my first order from Zenni…)

5$ off link:

Alternatively, if you don’t want to hack your glasses, I recommend the headband based magnifier with light in this amazon affiliate link:

Total cost? This set of glasses only cost me $54 (now that I know what I’m doing) but I did waste another $50 for a different set of bifocals before realizing that the standard bifocal inset area was too low for my needs, and that I’d have to modify the prescription by swapping the left/right eye so that I could rotate and swap the lenses.

Here is a video about the procedure:


Lightfield capture to Looking Glass “Quilt” image, scripted on the command line

I set up this still life scene to play with lightfield capture for my looking glass portrait device. Of course it has a few lenses in it so you can see the light go through the different lenses as you move your head back and forth.

To actually capture a “lightfield” you need to take photos of the scene from multiple locations (preferably in a controlled / regular pattern). To do this I put my phone on a skateboard and rolled it across the table from left to right while recording a video. This gives me 30 pictures per second with 1280×1920 resolution.  You can see this as a vertical video on the YouTube “Shorts” platform here:

To extract the individual images from the video was a single command line:

ffmpeg -ss 00:00 -i left-to-right.mp4 -t 00:02  out%05d.jpeg

Unfortunately for me, the “input image sequence to make a lightfield hologram” provided by Looking Glass Studio software doesn’t work unless you have a “real” 3D graphics card. The integrated Intel graphics built into my laptop just wouldn’t cut it, so no lightfield magic for me.

BUT, if you can generate a “quilt” image, the Studio software will import that and put it on the Looking Glass Portrait device for you so you can get a 3D hologram from your video.  The trick is to generate the “quilt” image (which is just 48 views tiled into a single image in the exact correct size and format) from your sequence of images.

First, you need to convert each image to the proper aspect ratio (4:3, or 0.75) and size (480×640 pixels).  The command line below uses ImageMagic to do this, and also flips the images upside down (important for when we tile them together, so we can tile a lot of upside down images, and then flip the resulting tiled image to get them in the proper format for LookingGlass….) I’m also putting them into a separate “flipped” directory to preserve the original images.

mogrify -flip -resize 480x640^ -gravity center -extent 480x640 -path ./flipped out*.jpeg

Once we have them properly resized, we tile them into the special Looking Glass Portrait High Res quilt, which is an 8×6 tile (48 images exactly) at 3840 x 3840 pixels.
The leftmost image from the scene (first image in the video) should be at the bottom left, then the images advance across the row and then up the columns until they
end with image number 48 at the top right.

# The -tile 8x6 should be obvious
# The -gemometry 480x640^ means to make each image 480x640.
# the ^ means  resize the image based on the smallest fitting dimension.
# (redundant here, as they should already be sized correctly by the previous step)
# +0+0 means no border.

montage out000*.jpeg -gravity center  -tile 8x6 -geometry 480x640^+0+0    tempoutput.jpeg

This results in a tiled image with the leftmost image in the top left and the rightmost image in the bottom right…but since we “-flip”ed the images initially, we can now “-flip” this entire output image and re-name it to the proper format for the Looking Glass Studio software to recognize it as a quilt image:

convert -flip tempoutput.jpeg output-qs8x6a0.75.jpeg


All that is left to do is to import the quilt image into the Looking Glass Studio software and sync it to your device.

(Or, if you are a beta user of the “blocks” web based embedded hologram service…you can upload it there and then embed the resulting hologram in webpgaes…)

You can download all of my source data and the scripts I used to create the quilt here:

Fixing my Neato X11 robot vacuum LCD screen

I’ve lived with a blank screen on my Neato X11 vacuum robot for a few years, but recently the robot started to beep error messages and refused to start up correctly, and I couldn’t figure out what the problem was without the screen.

So I found this thread and this specific post and decided that injecting 12 volts to the c5 line would be worth trying (I’m NOT going to go to the effort of replacing the entire LCD, especially if I have to remove polarized sheets and reverse it ;> )

I used a 78L12 12v 100ma linear regulator (TO-92 package) because it was inexpensive and small.

Of course, I added in a lot of hot glue for stress relief….

Thanks to AlainCAN, this fixed my LCD and I can now read the error message (fan was stuck, I found/removed a rice grain and that fixed things right up!).

Unfortunately, I somehow appear to have broken the LED’s (backlight for LCD as well as the button LEDs). I’m not sure if this is related to this throwaway line in Alain’s post:

By the way, don’t forget to replace the C10 capacitor as it can cause trubbles later (dimmed light green led).

Or perhaps I just forgot to plug something in….. but I can read the screen, which is better than having LED’s without being able to read the screen, so I’m going to count it as an overall success.