Thursday, March 01, 2007

F'ing Specks!

I have to indulge my inner (or outer) tech geek with this post. I'm not sure all of you will find this interesting since I know only a couple of you have SLR cameras, but if I can educate at least one person who may be thinking of buying one then this will be worth it.

A little while back I briefly mentioned the problem I have been having with specks on my photos. I've been doing some research, and I've come to find out that this problem is very real. It is also a real pain in the ass!

Digital cameras use a sensor to create the image that becomes a digital picture. When dust or crud gets on this sensor, you get specks. This problem is aggravated by the fact that the sensor is electrically charged when the camera is powered on, and this tends to draw particles to the sensor and make them stick. The specks show up much more in images when you use a small aperture. Here are some examples:

This picture was taken at an aperture of f32, which is the smallest I could get with this lens. Looks terrible! (click for larger view of any of these photos)

I reduced the aperture to f18. Better but you can still see specks.

This was from the other day with an aperture of f20. There's even a hair in there!

Obviously the problem shows up more on plain backgrounds. And a lot of the specks can be cleaned up with software, but I thought my days of cleaning up dust and scratches ended when I started using a digital camera. Guess not. And if the blobs end up on a background that is not uniform, they can be very hard to fix even with editing.

Now, this problem mainly occurs with SLR cameras. Since lenses on SLR cameras are changed out quite frequently, this gives an opportunity for the camera body to be open to the outside air when a lens is removed. If you don't have removable lenses, I guess this problem could still happen, but it probably wouldn't be nearly as bad. Since one of the most important reason to use an SLR is to use different lenses, this problem really sucks!

Currently there is only one camera that I know of that has a self-cleaning sensor - the Canon Digital Rebel XTi. Which happens to be the model that came right after the one that I bought. If I had known about this problem before I bought my camera, I may have waited for the newer model. I guess you could say that I should have done more research before this purchase, but I feel almost like I am getting a defective piece of equipment.

You may wonder why this problem wouldn't occur with film cameras. Actually, it does, but it isn't as noticeable because the dust settles on the film frame that is currently ready to be exposed. When you take a picture and the film advances to the next frame, the slate is wiped clean so to speak. A digital sensor is always in the same position, so the dust can just keep on building up over time.

Luckily, there is a way to clean the sensor. I have been using canned air to very gently blow the dust off the sensor. Canon specifically recommends that you not use canned air because they say the air flow is too much and if liquid comes out when you spray it can ruin the sensor. But I have found that if you barely press down the trigger, you can make the air come out much slower. And as long as you don't spray the air while holding the can upside down, no liquid should come out. But it still makes me kind of nervous. There is a brush available that is supposed to do a pretty good job, but it ain't cheap. I have one on order and should receive it soon.

So the lessons are: if you have a digital SLR, don't use a small aperture unless you really need to! And make sure you're OK with this problem or are willing to buy an expensive brush to fix it if you are thinking of buying an SLR (or buy the XTi).

Today's birthdays are brought to you by VisibleDust, makers of the aforementioned brush!



Blogger Anna said...

This is a very timely and educational post for me. Thanks! I am in the market for a digital SLR. I have been looking at the Nikons (D70, specifically). If it doesn't have the built in cleaner thingie, I may have to reconsider. Do you have an opinion on the Nikon D70?

3/01/2007 4:31 PM  
Blogger hollibobolli said...

I like the "twisting off" label.

I have no idea if I have specks - because all of those pics had specks - no why? Because I see GAWD AWFUL floaters all the time, because I think my eyeballs are getting ready to pop loose. Yet another thing to worry about. Maybe I need to get me some of that canned air. Blow off my lenses.

I got a tiny naked baby behind me, singing about tiny naked babies - and apparently, she has nothing in her hand. she just told me "I don't have anything in my hand." Sounds suspicious to me.

3/01/2007 4:32 PM  
Blogger hollibobolli said...

Now she wants to know whose ear that is.

3/01/2007 4:32 PM  
Blogger JC said...

anna - the D70 is a very nice camera. As far as I have been able to determine, the Canon digital Rebel XTi is currently the only camera with the self-cleaning sensor right now. But I would expect other manufacturers to come up with one on their upcoming models. And I have no idear how well the self-cleaning sensor works, it may still not be as good as physically cleaning the sensor. I actually received my brush in the mail today, so I'll post about how well it works after I've used it. It comes with this spinning gizmo to electrically charge the bristles. Kit with 2 types of brushes and spinner - $127!!!! Not cheap, but cheaper than replacing a sensor from cleaning it with something that may damage it.

h - thanks, it came down to "twisting off" or "bowing up". I need catchier titles for my other tags. I have a big floater in my left eye. Annoying. Naked babies!!!!!

3/01/2007 5:55 PM  
Blogger paintergirl said...

I like the twisting off too.

mmmm...Dirk Benedict. I LOVED Lt. Starbuck when I was a teen. He was a rich man's Sawyer(Lost).

You are really quite teed of aren't you about the whole specks in the camera?

We have a Canon c50 and well I don't pay attention to specks. Maybe my blog today will expalin why.

3/02/2007 8:09 AM  
Blogger REENblack said...

I got the xti for christmas as a replacement for my 35mm rebel I got when I was 16. I absolutely LOVE it!!! I dont know all the technical stuff (like the f stop that I'm guessing I should know about), but I love taking pictures and want to get better at it and possibly make a career out of it--I should probably take some classes, huh?!

3/02/2007 8:42 AM  
Blogger JC said...

pg - I love that someone else besides me dug the Dirk Benedict reference!

Reen - You can learn a lot from reading books about photography. Digital cameras are great for learning photography because of the instant feedback. Although sometimes things look a lot different on the tiny LCD screen than they do on the computer!

An F-stop is the same as the aperture setting. Basically the higher the aperture or f-stop number, the more depth of focus. So more stuff from front to back in the picture will be in focus. If you want a nice blurry background but a sharply focused foreground (like for a portrait), you will want to use a smaller f-stop. One drawback with a higher f-stop is that you will have to slow down the shutter speed to compensate for less light entering the lens. There's your first lesson!

3/02/2007 9:55 AM  
Blogger REENblack said...

Thanks jc, that actaully explained a LOT!!!

3/02/2007 12:56 PM  

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