Author Topic: A77 spots in small aperture images...  (Read 4603 times)

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Offline CHOLLY

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A77 spots in small aperture images...
« on: September 18, 2014, 02:46:53 PM »
I have been experimenting with depth of field with all my lenses, trying to determine the best setting for each for maximum DOF.

A couple of weeks ago I had taken some pictures at a beach and noticed spots in the finished images on my HD monitor.

So... naturally I cleaned all my lenses THORUOUGHLY.

The next week I took some sunset pictures on a local Dam.

SAME result... but I noticed something; lens choice didn't matter as the spots were in the SAME location regardless of which lens was attached.

...So naturally, I cleaned my sensor THOROUGHLY.

But I also noticed that SOME pictures had spots and others did not.

EVERYTHING shot f/20 and up (ESPECIALLY f/22) was spotty. Below f/20 and the images were clean.

So yesterday I tried different lenses at f2.8 through f/32 in broad daylight, short exposure time conditions.

SAME RESULT!

The spots are aperture dependent... nothing else matters.

Has anyone else encountered this situation or problem?

My next step is a professional sensor cleaning, but I'm afraid that may NOT make any difference. :(
« Last Edit: September 19, 2014, 05:50:40 AM by CHOLLY »
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Offline Faldrax

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Re: A77 spots in small aperture images...
« Reply #1 on: September 18, 2014, 03:16:01 PM »
Do you have a sample image to share?

It does sound like dust on the sensor, though I suppose it could be dust on the mirror (not sure if this has a similar effect, but would imaging it would be aperture dependant as well).

How did you clean the sensor?
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Offline AScot

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Re: A77 spots in small aperture images...
« Reply #2 on: September 19, 2014, 08:20:45 PM »
It sounds very like dust on the sensor. here is a link to how to check for dust on your sensor, I would use a blank white wall. Here.

If you are using a very small aperture, dust on the mirror could still be in focus when it hits the sensor. That may be your problem. If you use, say f16 or larger, that mirror dust will be out of focus when it hits the sensor and therefore be next to invisible. It is easy to remove dust from the mirror, just be very gentle.

Taking photographs using an aperture of f22 and smaller is not advised as it introduces lens diffraction and can occur on some lenses at f16 and smaller. instead of using small apertures to maximise your depth of field practise using the Hyperfocal distance method. Here is a calculator to determine the Ideal Hyperfocal distance for all cameras, f stops and focal lengths. HERE.
« Last Edit: September 19, 2014, 11:28:05 PM by AScot »
Sony A7, A850, A77, A700 || Sony>> 70-300G, 28-75 f2.8 SAM, 16-80CZ, 50 f1.4, FE 28-70 OSS, FE 24-70CZ f4 OSS, LA-EA4 || Minolta>> 300 f4 G HS, 200 f2.8 G HS, 100 f2.8 (D) Macro, 50 f1.7, 28 f2.8, 28-135 f4-4.5, 70-210 f4, 500 f8 Reflex, TC x 1.4 HS, TC x 2 HS. || Sigma 21-35 f3.5-4.2. || Tamron SP 24-135.

Offline CHOLLY

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Re: A77 spots in small aperture images...
« Reply #3 on: September 20, 2014, 05:35:03 PM »
Do you have a sample image to share?

It does sound like dust on the sensor, though I suppose it could be dust on the mirror (not sure if this has a similar effect, but would imaging it would be aperture dependant as well).

How did you clean the sensor?

AScot hit it on the head!

The sensor is clean, but the back side of my mirror was not!

(I never thought to clean the BACK side of the mirror!)

Thanks guys!
« Last Edit: September 20, 2014, 05:36:38 PM by CHOLLY »
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Offline CHOLLY

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Re: A77 spots in small aperture images...
« Reply #4 on: September 20, 2014, 05:39:25 PM »
BTW, I have printed out those charts for each of my under 100mm lenses and keep them in a pouch on my big go bag.

The old Minolta lenses are easy because the short focal length models have depth of field scales on them. Sony chose to leave that feature off though. :(
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Offline retoohs

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Re: A77 spots in small aperture images...
« Reply #5 on: September 21, 2014, 04:30:00 AM »
Is this the translucent mirror? I was under the impression the advice is not to touch these. I used to have a similar problem with my A77 which has gone on to greener pastures. Wish I'd known I could clean the mirror. The A99 I now have seems to have better auto sensor cleaning than the A77 and touch wood have had no dust problems to date.
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Offline AScot

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Re: A77 spots in small aperture images...
« Reply #6 on: September 21, 2014, 04:51:25 AM »
Using a blower to clean the mirror, after removing it, is quite safe if you are careful. However you should not touch the surface as it is quite fragile and can be damaged. If you do damage it Sony sells do it yourself replacement mirrors for an arm and a leg at a reasonable price. ???
Sony A7, A850, A77, A700 || Sony>> 70-300G, 28-75 f2.8 SAM, 16-80CZ, 50 f1.4, FE 28-70 OSS, FE 24-70CZ f4 OSS, LA-EA4 || Minolta>> 300 f4 G HS, 200 f2.8 G HS, 100 f2.8 (D) Macro, 50 f1.7, 28 f2.8, 28-135 f4-4.5, 70-210 f4, 500 f8 Reflex, TC x 1.4 HS, TC x 2 HS. || Sigma 21-35 f3.5-4.2. || Tamron SP 24-135.

Offline CHOLLY

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Re: A77 spots in small aperture images...
« Reply #7 on: September 21, 2014, 06:44:24 PM »
I used my LensPen Sensorklear brush to clean it...
There are people who actually think LENS stabilization is better than sensor shifting!