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Clean SLT mirror like you would the sensor?

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sybersitizen View Drop Down
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Post Options Post Options   Quote sybersitizen Quote  Post ReplyReply Direct Link To This Post Topic: Clean SLT mirror like you would the sensor?
    Posted: 29 October 2016 at 08:39
Originally posted by pdeley pdeley wrote:

Just wondering: do you think the dust spot and fiber got onto the sensor in between your shot of the wall siding at 8m and the blue sky shots?

Yep. After the first round of testing I removed the first obstruction, and the next day inserted the second (similar) obstruction for the second round. The obstructions were taped against the rear of the mirror frame, so I had to work with the mirror raised both times. There was much futzing around in the mirror box with no lens attached, meaning lots of opportunities for sensor 'contamination'.
 



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Post Options Post Options   Quote pdeley Quote  Post ReplyReply Direct Link To This Post Posted: 29 October 2016 at 03:04
Originally posted by sybersitizen sybersitizen wrote:


I just shot a quick simulation of 'stuff' on the mirror of my A55 using a 24mm lens focused at about 8 feet. The stuff in this simulation is a strip of cellophane tape about 1mm wide running approximately vertically across the mirror frame.

That orientation helps show the difference between how the top of the image is affected and how the bottom is affected.

f/22:



...

Of course in real life very few if any obstructions will be so big, but this shows us what is possible.



Originally posted by sybersitizen sybersitizen wrote:

Originally posted by neilt3 neilt3 wrote:

I would be very surprised if the lenses focal length makes any difference to the above example .

The size , therefor the spread of light , exiting the rear of the lens would have more of an effect .

You'll be pleased to know that your hypothesis is correct. I shot another similar obstruction using 24mm and 200mm lenses.


24mm f/22:



200mm f/22:



As we can see, the definition of the obstruction is similar in both cases when the apertures are the same.

The thing that changes is the perspective of the obstruction.

...

Even the dust spots on the sensor appear in slightly different places at the different focal lengths, which proves that they are sitting on top of the sensor sandwich, slightly in front of the actual sensor elements. (Yes, I cleaned the sensor and mirror after the test.) ;)


Just wondering: do you think the dust spot and fiber got onto the sensor in between your shot of the wall siding at 8m and the blue sky shots?
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Post Options Post Options   Quote neilt3 Quote  Post ReplyReply Direct Link To This Post Posted: 28 October 2016 at 19:53
Originally posted by QuietOC QuietOC wrote:

Originally posted by sybersitizen sybersitizen wrote:

Originally posted by molan molan wrote:

You don't clean a translucent mirror, then dirty you blow clean with air or replace as a spare part - expensive I might add.

Cleaning it will ruin it.
Already proven wrong. Be sensible about it and you won't ruin a thing.

I've cleaned the mirror just like a lens element. I managed to get something sticky on it and was able to get it clean again using just standard micro-fiber cloths and some moisture, and some blowing afterwards to get rid of the inevitable lint.


I've also cleaned the mirror's in my SLT cameras and LA-EA2 several times and not ruined anything .

Still in perfect condition and full working order .

The trick is to use a bit of care and attention and not be a clott and every thing will be well .
Anyone in doubt of their own abilities might be best off getting someone else to clean it , mirror or sensor .
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Post Options Post Options   Quote neilt3 Quote  Post ReplyReply Direct Link To This Post Posted: 28 October 2016 at 19:41
Originally posted by sybersitizen sybersitizen wrote:

Originally posted by neilt3 neilt3 wrote:

I would be very surprised if the lenses focal length makes any difference to the above example .

The size , therefor the spread of light , exiting the rear of the lens would have more of an effect .

You'll be pleased to know that your hypothesis is correct. I shot another similar obstruction using 24mm and 200mm lenses.

24mm f/5.6:



200mm f/5.6:



24mm f/22:



200mm f/22:



As we can see, the definition of the obstruction is similar in both cases when the apertures are the same.

The thing that changes is the perspective of the obstruction. With the 24mm, the light cone originates nearer to the sensor plane, so the obstruction appears nearer to the edge of the mirror. With the 200mm, the light cone originates far from the image plane; its rays are more cylindrical, so the obstruction appears more centered.

Even the dust spots on the sensor appear in slightly different places at the different focal lengths, which proves that they are sitting on top of the sensor sandwich, slightly in front of the actual sensor elements. (Yes, I cleaned the sensor and mirror after the test.) ;)


Thank you for taking the time to do this .
It's interesting that the dust on the sensor "moves" on the image depending on what lens is used .
I wouldn't have thought the filter pack on the sensor would have made that much diferance .
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Post Options Post Options   Quote sybersitizen Quote  Post ReplyReply Direct Link To This Post Posted: 28 October 2016 at 18:22
Originally posted by molan molan wrote:

Originally posted by sybersitizen sybersitizen wrote:

Originally posted by molan molan wrote:

You don't clean a translucent mirror, then dirty you blow clean with air or replace as a spare part - expensive I might add.

Cleaning it will ruin it.

Already proven wrong. Be sensible about it and you won't ruin a thing.

No, as I said you can use air, but you can't clean it like a sensor, it will break.

Done that, so I know what I am talking about. You might be able to use a brush though, but most wet or dry sensor cleaning tools will ruin it.

You said 'Cleaning it will ruin it.' That's wrong. I've physically cleaned my mirrors, probably dozens of times since 2010, and have never ruined them.

You should have said 'I tried to clean mine and I ruined it.' That would have been right.
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Post Options Post Options   Quote stiuskr Quote  Post ReplyReply Direct Link To This Post Posted: 28 October 2016 at 17:41
Some people can clean a translucent mirror with no problems, some people can't clean a translucent mirror with breaking it. There are some things that certain people shouldn't do.
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Post Options Post Options   Quote molan Quote  Post ReplyReply Direct Link To This Post Posted: 28 October 2016 at 14:11
The sensor is rugged, the morris however is as fragile as paper.
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Post Options Post Options   Quote molan Quote  Post ReplyReply Direct Link To This Post Posted: 28 October 2016 at 14:10
Originally posted by sybersitizen sybersitizen wrote:

Originally posted by molan molan wrote:

You don't clean a translucent mirror, then dirty you blow clean with air or replace as a spare part - expensive I might add.

Cleaning it will ruin it.

Already proven wrong. Be sensible about it and you won't ruin a thing.


No, as I said you can use air, but you can't clean it like a sensor, it will break.

Done that, so I know what I am talking about. You might be able to use a brush though, but most wet or dry sensor cleaning tools will ruin it.
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Post Options Post Options   Quote QuietOC Quote  Post ReplyReply Direct Link To This Post Posted: 27 October 2016 at 17:24
Originally posted by sybersitizen sybersitizen wrote:

Originally posted by molan molan wrote:

You don't clean a translucent mirror, then dirty you blow clean with air or replace as a spare part - expensive I might add.

Cleaning it will ruin it.
Already proven wrong. Be sensible about it and you won't ruin a thing.

I've cleaned the mirror just like a lens element. I managed to get something sticky on it and was able to get it clean again using just standard micro-fiber cloths and some moisture, and some blowing afterwards to get rid of the inevitable lint.
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Post Options Post Options   Quote sybersitizen Quote  Post ReplyReply Direct Link To This Post Posted: 27 October 2016 at 17:17
Originally posted by molan molan wrote:

You don't clean a translucent mirror, then dirty you blow clean with air or replace as a spare part - expensive I might add.

Cleaning it will ruin it.

Already proven wrong. Be sensible about it and you won't ruin a thing.
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Post Options Post Options   Quote Snegren Quote  Post ReplyReply Direct Link To This Post Posted: 27 October 2016 at 15:44
I had mine cleaned. Inexpensive, good as new afterwards
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Post Options Post Options   Quote molan Quote  Post ReplyReply Direct Link To This Post Posted: 27 October 2016 at 10:18
You don't clean a translucent mirror, when dirty, you use a blower to clean with air or replaces it - expensive I might add.

Cleaning it like a sensor, will ruin it.

Edited by molan - 28 October 2016 at 14:07
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Post Options Post Options   Quote sybersitizen Quote  Post ReplyReply Direct Link To This Post Posted: 25 October 2016 at 18:06
Originally posted by neilt3 neilt3 wrote:

I would be very surprised if the lenses focal length makes any difference to the above example .

The size , therefor the spread of light , exiting the rear of the lens would have more of an effect .

You'll be pleased to know that your hypothesis is correct. I shot another similar obstruction using 24mm and 200mm lenses.

24mm f/5.6:



200mm f/5.6:



24mm f/22:



200mm f/22:



As we can see, the definition of the obstruction is similar in both cases when the apertures are the same.

The thing that changes is the perspective of the obstruction. With the 24mm, the light cone originates nearer to the sensor plane, so the obstruction appears nearer to the edge of the mirror. With the 200mm, the light cone originates far from the image plane; its rays are more cylindrical, so the obstruction appears more centered.

Even the dust spots on the sensor appear in slightly different places at the different focal lengths, which proves that they are sitting on top of the sensor sandwich, slightly in front of the actual sensor elements. (Yes, I cleaned the sensor and mirror after the test.) ;)
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Post Options Post Options   Quote neilt3 Quote  Post ReplyReply Direct Link To This Post Posted: 25 October 2016 at 11:37
Originally posted by amrep amrep wrote:

Very nice practical lesson! A picture is worth a thousand words :)
It also shows the importance of distance from the focus plane. The lower part of the mirror is very roughly double the distance from the focus plane than the upper part. It corresponds to more blur in the upper part of the shadow . (The projected image is upside down.)

A blocking regular shape across the entire light cone is far more detrimental/visible than point-like spots or dust randomly scattered. Wide angle lenses are more prone because of the large DOF.


I would be very surprised if the lenses focal length makes any difference to the above example .
Larger DOF is seen with wide-angle lenses on the scene being shot , ie , outside the camera .
Any focal length of lens with the same sized rear lens element , at the same distance from the sensor "sends" the light to the sensor the same way .

The size , therefor the spread of light , exiting the rear of the lens would have more of an effect .
Depending on where the object is on the mirror a 50mm lens with a maximum aperture of f/2 has a tighter beam of light , though still falling over the full sensor .
A 50mm lens with an aperture of f/1.4 has a larger area that the light is coming from , so would be more diffused .

Even stopped down , the light is coming from a larger surface area of glass as the aperture blades are set back in the lens .

If you have more time on your hands to test this theory , feel free !
I'm off to work now.
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