NEX 6 - Dark spot on photos

Started Jun 7, 2013 | Discussions thread
GaryR60 Contributing Member • Posts: 656
Re: NEX 6 - Dark spot on photos

Digital Nigel wrote:

GaryR60 wrote:

Digital Nigel wrote:

EinsteinsGhost wrote:

Hooterville wrote:

Thanks, did not even realize the f stop was on 29.  I just shot those and ran off to work. Hopefully I'll have some time to play with the camera over the weekend.

Generally, you will start seeing dust spots on sensor at about f/11. I generally set f/16 and point camera towards a white sheet/blank wall and move it around. If I see spot(s) moving as well, its time to clean the sensor.

Or keep the aperture below f/11 and don't worry about dust on the sensor...

It doesn't matter what aperture you are using. If you have dust spots on your sensor, they will show up no matter the aperture. What will reveal them, more than the aperture selected, is if they fall in any clear area of the photo, like a cloudless, bright sky. Another thing, not cleaning your sensor will only allow the dust spots to get worse and they may even begin to eat into the sensor surface, depending upon what other microscopic crud may be in the dust.

I have a set of 20 test shots I took for another purpose (to check out the image quality of my newly purchased UWA with my long-owned, but rarely-used 16mm pancake lens). I took a series of hand-held shots at all apertures, mainly to look at how edge sharpness varied with aperture, but they accidentally also showed me I have some sensor dust which is only evident at very small apertures. It only became evident because I happened to include a lot of sky in the pics, even though that wasn't the purpose of the shots.

I've picked out half a dozen of these images from the series (all taken from the same spot, but hand-held rather than on a tripod, so the view varies a little between them). All shots were taken in RAW and processed using DxO; they were shot at an effective 12mm focal length, though the exif data says 16mm as the camera doesn't know the UWA is fitted. They are re-sized for uploading, but not cropped.

You're arguing apples and oranges, here. The dust spot is still there on your sensor, regardless of what aperture setting you've used, and I'll wager that if you put any of these test shots into, say, Nik's HDR Efex Pro, and cranked the Structure slider all the way to the right, it would reveal the dust spot in every one of them.

f/4: no sensor dust apparent, but less than ideal sharpness at edges

f/8: no sensor dust spots apparent, and quite acceptable image quality

f/11: a few very faint sensor dust spots apparent

f/14: sensor dust apparent, but not yet very annoying

f/18: more sensor dust spots visible, starting to become annoying

f/22: numerous, intrusive sensor dust spots

As you can see, the dust spots are simply not an issue below f/11 (unless you go pixel peeping), when they first start to become apparent. At f/14, they are very visible, and by f/18, they're getting annoying. As I hardly ever take 'normal' pictures at such small apertures, I wasn't even aware of the dust spots on my NEX-7's sensor.

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