Blemish on photos.

macolgan

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I've recently noticed a small circular blemish is appearing on all my photos. It is always near top-centre but can only really be seen if that area is bright sky or white cloud etc.

I've checked that it's not the lens's so must be the camera. I've checked the bypass filter following nikons instructions but can't see anything on this that would explain the "blob" which is a dull grey and around 4-5mm on my mac's full screen display - 23".

Can anyone shed any light on the subject ?

Regards........ macolgan.

basflt

its dust
use an Arctic Butterfly Brush to clean your sensor
http://www.visibledust.com/products3.php?pid=3

if that dont help , use Swaps
http://www.sensorswab.com/swabproduct.htm

pathfinder

If you only have one dust bunny, you might ignore it, and just clone it out while editing your images.

Dust bunnies are much less apparent at wider apertures, and are more noticeable at f8 and smaller apertures. ( f11, f16, f22, etc )

paddler4

I'd get rid of it, personally.

Before using a brush, I would use a blower (not canned air). if that does not work, use a static brush. You can get a good static brush and a rocket blower together from Copper Hill for about 1/4 of the price of an Arctic Butterfly. If those two steps don't work, the last step is a wet cleaning. I rarely get that far--the first two steps usually do it.

angevin1

Did you try your in-menu cleaning first?

TonyCooper

Dust on the sensor. Usually spottable when the photograph includes
sky where the spot is. Yours is clearly visible.

A blower (Giotto Rocket recommended) is available from any camera
store. Instructions for removing dust should be in your camera's
manual. You have to follow the camera's procedure to do this.

I would strongly discourage using a brush or swabs. If it gets to
that point, having the sensor professionally cleaned is recommended.

jjbong

TonyCooper wrote: »

I would strongly discourage using a brush or swabs. If it gets to
that point, having the sensor professionally cleaned is recommended.

That used to be my opinion, as I was worried about damaging the sensor.

Then I watched a Scott Kelby Training class on sensor cleaning by Laurie Excell,
and I changed my mind. She has a very methodical approach, starting with using
the built-in sensor cleaning, then the air blower, then the Actic butterfly, then
swabs, stopping when the dust is gone. Key to this is a loupe, so you can actually
see the dust (and know where to blow). She also points out that you're not cleaning
the sensor, but rather the filter in front of it. Rightly or wrongly, that put my
mind at rest.

She says she cleans after every shoot, by the way.

It's been maybe 9 months since I watched that, and I clean after every shoot where
I change lenses. Almost every time I change lenses, I end up with some amount of
dust, despite being careful about shielding my camera from the wind.

There's a bit of investment in getting all of the stuff to do the cleaning, but where I
live, it's $60 a pop for a sensor cleaning at a camera shop.

Also, I've noticed that I rarely have to go beyond using the blower, and almost never
have to use the swab. I was in Turkey for a month, and never had to go beyond the
blower. Clearly, this will vary depending on where you're shooting. But based on my
experience, you might be able to get by with a loupe and a blower.

macolgan

Thanks everyone.... it was indeed a dust spec ! So small I could only see it using a loupe, as advised, and held below strong light.

It took three separate attempts though to dislodge the little blighter. Test photos this morning confirm it gone.

I will have to maintain " due diligence " from now on. Oh... and invest in some of the professional gear recommended.

Regards to all once again..... macolgan.

aj986s

FWIW, I've also discovered that an easy way to check for sensor dust is to set the camera to a small f-stop and long exposure, at least 1/4 second. Then, focus on a blank, white (or nearso) surface, like a wall or ceiling. During the exposure, move the camera slightly; focus isn't realy critical. Any dust will show up as a distinct black dot on the image. I'm not sure if this is exactly what's happening, but it appears to me that during a still image, the processor tries to blend the dust into the background. But when the image is moving, the dust stays static relative to the image/sensor, and become much more pronounced in the final image.

macolgan

aj986s wrote: »

FWIW, I've also discovered that an easy way to check for sensor dust is to set the camera to a small f-stop and long exposure, at least 1/4 second. Then, focus on a blank, white (or nearso) surface, like a wall or ceiling. During the exposure, move the camera slightly; focus isn't realy critical. Any dust will show up as a distinct black dot on the image. I'm not sure if this is exactly what's happening, but it appears to me that during a still image, the processor tries to blend the dust into the background. But when the image is moving, the dust stays static relative to the image/sensor, and become much more pronounced in the final image.

Hi and thanks for the above. I just set a blank webpage on my mac and carried out the procedure you describe.
The page actually wasn't that "white" but by setting the exposure sliders around, I could get the screen to be really bright, and hence show up any " defects " that might be there. Zooming right in on the screen and moving the "photo " about, let me study in very close detail.
Thankfully, nothing showing from the camera, but this does show up some faint marks and blemishes on my mac's screen . Not on the surface that is, but then the mac is around 5 yrs old now. Wont waste my normal viewing I'm sure !

Regards.... macolgan.

Sam

Just a quick note: I highly recommend buying a sensor loupe. You can see the dust specks quickly and easily. The loupe adds speed and ease to the sensor cleaning process.

You will not be sorry you purchased one.

Sam

jjbong

One other thing. I have a Canon 5D Mk II, and I don't know whether this applies to others.

The camera cleans the sensor when it is powered off (or, at least, there's an option to do that). You can also tell it to
clean manually when it's powered on. When you do that, it makes a lot more noise and takes longer than the automatic
cleaning on poweroff. I concluded that the cleaning was more aggressive.

Since then, I clean the sensor manually after I change lenses. I've noticed much fewer dust problems since.

aj986s

macolgan wrote: »

Hi and thanks for the above. I just set a blank webpage on my mac and carried out the procedure you describe.
The page actually wasn't that "white" but by setting the exposure sliders around, I could get the screen to be really bright, and hence show up any " defects " that might be there. Zooming right in on the screen and moving the "photo " about, let me study in very close detail.
Thankfully, nothing showing from the camera, but this does show up some faint marks and blemishes on my mac's screen . Not on the surface that is, but then the mac is around 5 yrs old now. Wont waste my normal viewing I'm sure !

Regards.... macolgan.

I re-read your post and wondered if you were only looking through the viewfinder, versus actually snapping a picture. I've found that you need to take a picture in order to see the dust in the final digital image.