What is the cause of these round spots on my photograph?

Question

Is this a finger print on the lens? I don't know.
What can be the cause of the round spot on this photograph?
I have many times cleaned the lens with my fingers, never saw anything like this before.

Canon PowerShot SX210 IS

Answer

Spots like this are due to something on or very, very near the sensor. See Dust-like speck visible every few pictures — is it dust, or worse? for another example. Dust in or on the lens can't cause this problem, because, like lens scratches, they'll be so far out of focus that the effect is undetectable (in the same way a window screen becomes invisible when focused far away through it).

On an SLR, you can access the glass protecting the sensor, and it's not much of a worry, since you can clean this. And automatic cleaning technology has gotten better. With my first couple of DSLRs, this was a constant annoyance. The first one had no real self-cleaning mechanism, and the second did, but it was ineffectual. With my current camera, which I got in 2009, I've never once had a problem with dust, and I change my lenses a whole lot more than I did five years ago.

With a compact camera, though, the whole thing will need to be disassembled, and this isn't something you can easily do at home — they're not made to be user serviceable. A camera service center will be able to do it, and if they're feeling charitable may in fact clean the sensor under warranty for free. Out of warranty, or if they decide the dust is due to environmental conditions you should have been more careful about, it's generally unreasonably expensive. (I once paid $100 to have a Fujifilm F31fd cleaned in this way.)

So, in this lovely world of disposable consumer gadgets, most people consider this time to get a new camera. If you get a new camera which doesn't have either built-in sensor cleaning or a way to access the sensor for manual cleaning, consider one with environmental sealing (waterproof is also dust-proof).

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Dust-like speck visible every few pictures — is it dust, or worse?

Question

I seem to have to dust-like speck on my Sony Cybershot S950's lens, but it appears randomly every few pictures. Could something be going bad internally?

Answer

That sure looks like sensor dust, for which I'd recommend seeing the answers in the Best way to clean a DSLR sensor thread. The spot may appear "randomly" because it only appears when you're using a narrow aperture.

That said, it seems you don't have a dSLR, thus no interchangeable lenses which are what usually causes the situation where dust can get inside the camera body. I suppose it's possible that dust got inside the camera through some other way although I think that's a fairly rare occurrence.

If the camera is still under warranty, it's worth a call to the manufacturer.

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What is causing this white spot in every photo with my D90?

Question

Recently I noticed that the photographs from my D90 has an odd white dot in it. The dot is present in every image. The dot becomes clearly visible as I zoom into the image. I have attached a photo taken with dark background and marked the white spot.

What could be causing this white spot? Has any had such issues? Sample image with marked white dot http://imgur.com/trYbG

Answer

This is most likely a Defective Pixel. There's not much you can do about it aside from cloning it out in Photoshop when it is obnoxious. Are you doing a lot of long exposures? Back when I was doing astrophotography I'd see a bunch of dead pixels in my camera, but never saw them in regular use. So it may be related to sensor time.

You can always contact the manufacturer and see if they have a defective pixel policy. You may get it fixed!

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Hmmm, I just fully read the wikipedia article. By their definition, the pixel in the camera sensor would always be off, not always be on! But I tend to doubt that, on or off, they are still defective. This article over at Ken Rockwell's site calls them hot pixels. Same thing in my book. Hot, defective, whatever...

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How can I avoid soft dull “spots” in my pictures?

Question

Recently, I've been doing a lot more photography, particularly with my 100-400mm telephoto and 16-35mm wide. I am skilled enough that I can capture the shot mostly as I want with just the camera gear, requiring minimal post processing. I'm a huge fan of ETTR now, so most of my shots are overexposed to support more shadow DR and improve the noise performance of my el-chepo 450D body.

I've noticed quite a bit lately during post processing in lightroom that my sky's or any other lighter areas of my shots tend have spots on them. They are soft and dull to one degree or another (seems to depend on the zoom factor), so probably something either on the sensor or the lens. I'm having a hard time figuring out exactly what they are, as I try to use my lens pen brush before any shoot, yet I still have them. I am having to make quite a few healing corrections post-process to get rid of them.

Is there an easy way to identify where the spots are on my lenses? Once identified, if a quick brush of the outer lens element with a lens pen (or soft camel hair brush) doesn't do the trick, does that mean the spots are on my sensor? Is it possible there is particulate inside the lens body (all of my gear is less than a year old outside of my 450D body, and its all Canon L-Series gear, so I would home that I don't already have detrimental particulates floating around inside my lenses messing up my shots. :|)

Here are a couple examples. The spots are harder to see on screen, and I first noticed them when I printed a few of my more recent shots. There are quite a few, and the shot the examples below were taken from, where the sky took up about 30% of the top edge of the photo, there were probably 10-12 different spots, some of them darker, many of them lighter. The darker ones are the ones that are very visible in prints, where as the softer ones are not as visible, but still apparent enough to ruin an expensive print.

Answer

Some dust spots on the sensor will absolutely not shift with air-pressure (blowing) alone. To shift them you need to wet clean the sensor.

I was nervous the first time I did this as I can understand most people would be. But it is not that difficult or risky, basically it involves wiping the sensor assembly with a soft rubber "wand" with a cleaning fluid dampened wipe attached to it. At this point it's worth stressing:

You are not cleaning the sensor microchip itself you are cleaning a toughened piece of glass (the low pass filter) that sits on top of the sensor.

The only damage you can do (when using the correct fluid) would be to the delicate shutter curtains, so make sure the shutter is open and will remain open for long enough to clean the sensor. This usually means ensuring the camera's power source remains uninterrupted.

Eclipse fluid has been tested on all sensors and determined to be safe. It's basically just alcohol and will evaporate without residue. See:

http://www.photosol.com/guarantee.htm

Likewise PEC PADs are highly recommended to go with it. I suggest you get a kit that includes the basic rubber wand, fluid and pec pads, then replace the fluid and pads as they run out. This is a very cost effective solution compared to all in one wet cleaning solutions. All you have to do is wrap the pads round the wand and tape them each time.

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Why are those green spots on my photo?

Question

Took a pic with my 35mm Nikon lens last night, and got this light artifact. Is this something normal? Reflection? Is it dirt on my lens? How do I prevent this from happening? I think it only happened when there is backlighting.

UPDATE: new screenshot.

Answer

Looks like lens flare to me. Odds are there's a similarly-shaped pattern of lights in front of the camera (possibly behind/above the subject since you noted backlighting) and what you're seeing is a result of those lights being bounced around inside the lens. update: Now that you've posted an updated photo, one can see the chandelier which is being reflected either by the lens itself or possibly by a filter on the lens.

For more information, see the lengthy answers to What causes lens flare?

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How to prevent weird spots and stripes on photos of window glass?

Question

A few days ago I took photos of a nice curvy business center in another city. Later I discovered that many frames had weird artifacts on the glass, shown below as 100% crops.

An almost normal shot:

A spotty shot 46 seconds later:

A striped shot 9 minutes earlier:

All crops show the same windows.

I did check the sensor, it was clean. I used a CPL filter to control reflections. Unfortunately the artifacts are too small to notice on camera LCD without zooming in, so I did not notice them and did not experiment to lose them on spot.

What could have caused those artifacts and how could I prevent them in future?

Answer

Those look like features of the glass windows that are being revealed by the polarizer. I don't think there is any way to avoid them other than by not using the polarizer, or being careful with the filter orientation and lighting.

I've observed this effect many times in car windows. I can't find a technical explanation but I imagine it's to do with stresses in the glass when cooling which result in parts of the pane polarizing light as it passes through; this light is then filtered out by the polarizer on your lens, resulting in the dark patches.

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