Weird dots/smudges in photos taken at narrow apertures

[nishnishant]

<p>I noticed something very strange today when I took some photos at narrow apertures, f/36 mostly. There are 3 dots (smudges rather) in all the pics, and they are always at the same position. The pics were taken using a D40X with the 18-55 kit lens (non VR). All the pics were taken at ISO 100, f/36 and exposure time ranged from 2-6 seconds (but this didn't change the dots or their positioning in any way).</p>

<p>I've never uploaded pics here, so I hope it works right. Anyone knows what may be causing these?</p><div></div>

[nishnishant]

<p>Okay, here's another picture with the same smudges in the same spots.</p><div></div>

[nishnishant]

<p>And here's a 100% crop from Picture 2 showing the smudges.</p><div></div>

[mbwood]

<p>

<p >Those spots are caused by dust on your sensors AA filter. They are not normally in focus but when you stop down to ƒ32 they appear with more defined edges. If you take a picture of a light colored wall at an open aperture you will likely see spots that are much less defined but when the lens is stopped down they become much more visible. The simple way to eliminate the spots is to clean your sensor. </p>

</p>

[nishnishant]

<p>Oh, so it's not a lens issue but rather an issue with the camera sensor? I didn't think of that at all :-(</p>

<p>I was telling my wife that the lens is not worth a lot and so it's not a big deal to get it replaced with another. But if it's the camera it's bad news - I use a D80, she uses this D40x most of the time.</p>

<p>As someone who's never opened any part of the camera, I wonder if it's safe for me to attempt to clean this on my own.</p>

[kris-bochenek]

<p>That's just sensor dust it will happen no matter what try using an air blower and blow them out but make sure not to touch the sensor<br>

to check for dust take a picture of a white wall or sheet of paper at f/22 or higher and try cleaning it with air blower and check for results. Some dust is hard to get rid of in those cases you will need to use sensor brush or have it cleaned by Nikon.<br>

Regards,</p>

[nishnishant]

<p>Thanks both of you.</p>

[ronald_moravec1]

<p>Gillotos Rocket blower or have a repair person clean it. Put the camera in sensor cleaning mode which will open the shutter and raise the mirror exposing the AA sensor cover. Use the hand blower and you may be sucessful, sometimes not. It seems the longer it sits, the harder it is to remove. </p>

<p>If you were more experiened, I would tell you to clean it yourself. There are many threads on sensor dust and cleaning.</p>

<p>Also read up on Copperhill Method and Artic Butterfly.</p>

[paradoxbox]

<p>One thing a bit unrelated to your original query, but shooting with such narrow apertures is fairly useless for what I see in your pictures. You would be better off learning what "Hyperfocal Focusing" means. This will allow you to get everything in focus without stopping the lens all the way down to F36.</p>

<p>You see how your images have a kind of soft blurry dreamy appearance to them, it is being caused by diffraction. When your lens aperture gets too narrow it starts to bend the light which makes it look a bit strange / fuzzy in the final image. Avoid this by shooting at a max of F16 and using hyperfocal focusing to keep nearly everything in focus without losing sharpness. Only resort to F36 if you need to have both a very close object in the foreground and a very distant object in the background in focus; otherwise it's just a waste.</p>

<p>P.S. - Forget about trying to get the dust off. You will never get all of it and at F36 even tiny microscopic skin cells will show up on the image, even if you get it all off you'll put more dust right back on it when you go to put the lens back on. Fix the spots in photoshop with the spot healing tool or a similar tool if you must shoot at super narrow apertures.</p>

[bmm]

<p>I ahve a D80 and had similar issues after coming back from the Middle East (lots of fine sand/dust got in)... can report that while I got all worried and in fact got myself a lens pen kit 'just in case' a couple of really thorough concerted sessions with the blower have totally fixed my problem.</p>

<p>Start there and you should be ok, if not there are plenty of next steps - both DIY and through service outlets.</p>

[phototransformations]

<p>My guess is that the OP was trying for that soft effect, and the long exposure on the water, hence the f/36 aperture. Perhaps a ND filter would work better, though if overall softness is the goal, there's nothing inherently wrong with f/36.<br>

I'm usually able to get my sensor clean enough so that spots don't show up, even at f/36, using a SensorKlear pen. Wet cleanings should also get it that clean. If you close the shutter before replacing the lens, then the dust that gets into the mirror box when you put the lens back on doesn't necessarily get onto the sensor.</p>

[nishnishant]

<p>Thanks once again for the repies.</p>

<p>@Cory : thank you, I was not aware of hyperfocal focusing. I read up on it - interesting technique. I don't know if it'd have helped me here because I focused on the fountain but it may have helped reduce the diffraction.</p>

<p>@David : The soft look is mainly because it was windy, so the trees/leaves were in motion. My aim was to get a long exposure on the fountain in the middle and also on the flowing water. And yeah, I may have to get an ND filter to get longer exposure times.</p>

[kari v]

<p>ND filter (or two) is a very good idea. If you want long exposure with anything sharp in the image some day it isn't going to happen at f36. I don't even stop down my medium format lenses that far!<br>

With D40X/D80 f11 is usually all that is needed.</p>