Problem with dust in A7 and A7ii

[Angi_W]

I have been experiencing a problem with dust in both A7 and A7ii cameras. This dust can appear literally between shots, and when the lens hasnt even been changed - following professional cleaning at a camera shop. ( Even he said they are a nightmare to get totally free of dust- he can clean it and by the time the lens is on it has dust again).

I use mostly the same lens almost all the time so dont change lenses often, and now only change indoors in case of a breeze. I keep my lenses clean and blow with a rocket blower prior to changing lenses. I do everything we are supposed to do on changing lenses, pointing down, keep camera switched off, avoid a dusty atmosphere, change over quickly - I dont even breath when giving the sensor a bow or dry wipe!

The dust spots are definately on sensor not lens, and most of the time can not be seen by eye. 

Im sure most people would never notice them, but I do because I work in macro all the time and shoot mostly at F18 with a clean background.  Thing is that I enter a lot of competitions and I like to get everything right in camera - one of the competitions is only straight out of camera and they do not allow removal of dustspots, so I need to get my sensors spotless.

I have noticed the blowing it with the giotto rocket blower makes it worse every single time ( yet the same blower works on my partners 3 cameras ( Nikon and one is mirrorless). A dry swab does help but I cant even get less than 20 dust spots. Note they move around all the time - so not stubborn dust stuck to the sensor.

I know Im not the only person experiencing this, I have a few friends with the same issue - but they dont shoot macro with clean backgrounds so its not as noticeable for them. I know I can shoot at a wider aperture say F8 and they are a lot less visible - but I need to shoot at F18 for my speciality.

I love my Sony mirrorless, but if I cant resolve this soon Im going to have to change and sell all my equipment.

[darkframe]

Hi @Angi_W,

first off I'd like to ask you whether the image which you've presented is a dark frame (sic!)? That's a term rather common in astro photography. It's used to determine which spots are stars and which ones may be hot pixels or other sensor errors.

What bothers me is that obviously two different cameras are affected. However, in order to get closer to the problem I'd suggest that you produce a dark frame by yourself. Please, do stick to one camera body and one lens to begin with. Changing to and fro will not lead us anywhere.

So, for the dark frame take your camera into a room with absolutely (!) no light. Put the lens cap on, switch off the screen and, for our purpose, take a shot of e.g. 30 or 60 seconds. In order to be a 100% sure cover the view finder right after you've started taking the shot, just to be sure that there's absolutely no light around. The resulting black image is the so-called dark frame.

In case the sensor does not have any hot pixels or other problems the image should show black only without any spots (check that on your PC) or a few spots only. In Germany there's no common law about the number of "acceptable" hot pixels for camera sensors (actually a court said "none" in a judgement regarding a Canon camera). That may be different in the UK of course. In case you do see something similar to your image above I'd nevertheless say that something's wrong with the sensor.

However, if your dark frame is black completely you'll know that at least the sensor is okay. Actually, when looking at your picture I'm not too sure whether those white dots were caused by dust. They do seem to be too equal in size and somehow too sharp for dust particles. Here's an example of a picture taken with a dust particle on the sensor (cut from the image, original size):

Obviously that dust particle produced a blurred and darkened area. And yes, I'm sure that it was a particle on the sensor because I was able to remove it by simply using a dust blower, hence the following pictures were fine. 

So please do me a favour and do that dark frame test at first. If that runs okay we'll see what could be a different reason. 

Cheers

darkframe

[Angi_W]

Darkframe - thank you - this is my darkframe - its not looking good. Thing is that I only have about 10 dust spots at present - none of these show up. All dust spots move and change over time.

[IamNic]

Hello @Angi_W,

on first glance that looks to me like damaged sensor pixels - what irritates me though is the option "visualize spots" (in the lower right) is activated. Which may put a contour around the spots and show which area will be "inpainted".

I think the software you took screenshots of changes what the darkframe really would show. Can you upload the JPEG file only? Without taking a screenshot of the software you want to use for spot removal?

- Nic

[Angi_W]

That was in Adobe camera raw with visualise spots option and exposure wacked up 5 stops- Ive just taken another now and without the visualise spots option its just black all over.

[IamNic]

Hello @Angi_W,

then your sensor is not broken after all.

Now how visible are spots when you taken an image of landscape/the sky?

- Nic

[The_Black_Rose]

Hi Angi_W,

If the effect of the dust is visible in all of the photos taken even when you view them on the camera. I'd say get it inspected.

The service centre's number is +44(0) 1656867347.

Cheers,
The_Black_Rose

[IamNic]

Hello @The_Black_Rose,

kindly read the thread - the white spots are an overlay created by the software @Angi_W wanted to use for dust/spot removal. The real impact is probably much smaller if visible at all.

- Nic

[darkframe]

Hi @Angi_W,

---

@Angi_W  schrieb:

Darkframe - thank you - this is my darkframe - its not looking good. Thing is that I only have about 10 dust spots at present - none of these show up. All dust spots move and change over time.

---

well, I had a talk to somebody else a few minutes ago and he came up with a reasonable explanation for your bad result with the darkframe.

He said that with those modern cameras you should use a lower exposure time for the production of a darkframe. Reason is that the longer the exposure time is the warmer the sensor gets which might lead to so-called "hot pixels". Those would lead to an image like you've shown here. So the white dots may simply be hot pixels but no broken pixels.

Additionally you should switch on Long Exposure Noise Reduction (see here) as this would take care of the hot pixels. Well, maybe worth a try.

Cheers

darkframe