Can Sensors be protected from Dust While Changing Lenses

[melovesushi]

On 10/20/2015 at 8:22 PM, Al Pha said:

I already own (and use) giottas rocket and a wet clean system with illuminated magnifier. However, I think it is technically possible for camera manufacturers to include sensor covers in ILC cameras to eliminate or at least minimize the need to clean sensors. It would be nice to hear from a Sony voice whether or not this is possible!

totally agree , an in built sensor cover that is switched on and off during changing lenses would be ideal and is something that is essential , the only way i combat it is turning off the camera during a lens change and holding the camera sensor facing down or away from any obvious wind 

[Pieter]

On 3/27/2019 at 11:03 AM, RudiZ said:

The problem is that the Zoom lenses extend and so pump air inside the camera...With a Prime lens, you do not have dust on the sensor. My idea is when you have a Sony then you need an adapter for other lenses (Nikon, Tamron, Canon...) stick a glass (coated) from an optician inside of this adapter... maybe the optician can make this also because they fit the glasses.  

Zoom lenses don't pump air into the camera, they pump air from the outside into the lens and back the same way.

This sounds like just the thing for you. No need for a DIY workaround with adapters.

[Thad E Ginathom]

Doh! I was wondering what the effect of a whole new electro-mechanical assembly would be on size, weight and price. I'm an idiot: the mechanism is already there. Just close the shutter when the lens is being changed.

(read elsewhere today. Sorry, I don't remember the source for credit)

 

[Pieter]

1 hour ago, Thad E Ginathom said:

Just close the shutter when the lens is being changed.

I think this is a bad idea: the shutter is a very fragile and meticulous piece of hardware. The glass cover of the sensor is much less susceptible to damage, much easier to clean and if it does get damaged likely cheaper to fix than the shutter assembly. Besides, dust would still get on the shutter blades and be released into the camera as soon as the shutter is actuated.

Edited March 31, 2019 by Pieter
typo

[Thad E Ginathom]

2 hours ago, Pieter said:

the shutter is a very fragile and meticulous piece of hardware.

Ahh. Thanks for correcting me on that one.

[Wally The Confused]

On 3/27/2019 at 10:03 AM, RudiZ said:

The problem is that the Zoom lenses extend and so pump air inside the camera...With a Prime lens, you do not have dust on the sensor. My idea is when you have a Sony then you need an adapter for other lenses (Nikon, Tamron, Canon...) stick a glass (coated) from an optician inside of this adapter... maybe the optician can make this also because they fit the glasses.  

That is Spot On ! Even with those fixed lens zooms.

Any time you turn the camera on, and the lens extends , you create a vacum that can suck dust & pollen into the body, and sticks to the electrickly charged sensor. 

Somewhere on the internet, there is a brilliant youtube clip , showing what happens when you turn  a camera on, in a smoke filled box.

If the lens can extend.....then it is  NOT sealed !

There has to be a micro opening , otherwise the lens would not be able to move.

 

Cheers

Edited April 3, 2019 by Wally The Confused

[Chrissie]

40 minutes ago, Wally The Confused said:

There has to be a micro opening , otherwise the lens would not be able to move.

Wally, please don't spread this kind of nonsense claims.

Without an opening, micro or not, you would simple just be changing the internal air pressure, which would definitely not block the lens from moving.

If you want to read up on physics, this would be a good start.

[Pieter]

I guess Wally is right to some extent: if a telescopic lens were airtight then extending or collapsing it would change the enclosed volume and thereby create internal under- or overpressure. The lens would pretty much act like a spring: you would be able to extend it a little bit but it would revert back to its original position when released to equalize internal and external pressure.

That being said, like I mentioned in my previous post, it is indeed nonsense to claim that a telescopic lens pumps external air into the camera body. It does take in air when extended but this is blown out the same way when collapsed.

Telescopic zoom lenses generally do increase the chance of getting dust inside the lens if not properly sealed against dust. Fixed barrel zoom lenses like the 70-200 G(M) and the 18-105 G don't suck in external air so much when zoomed, so these lenses are less prone to getting dust inside the lens.

Edited April 3, 2019 by Pieter

[Pieter]

I'll have to rectify my previous post a bit: some lenses have a moving rear element, such as my E 55-210mm. The rear element moves outward when zooming in, thus creating underpressure in the sensor chamber.

Out of pure curiosity and a scientific mindset I taped off the rear side of the lens to see if I could create a vacuum between the rear lens element and the tape. I couldn't, indicating that there must be a vent in the lens which lets in external air into the rear part (and thus into the sensor chamber). Removing the tape and holding my hand over the rear side of the lens while rapidly zooming in and out, I could feel some airflow against my hand. Air that would normally be blown right onto the sensor.

I guess the air is sucked in through the tight seams in the lens so I wouldn't really worry about big dust particles, but it seems plausible that lenses with a moving rear element might pump some air (and dust) onto your sensor.

 

[Wally The Confused]

b

On 4/3/2019 at 3:54 PM, Chrissie said:

Wally, please don't spread this kind of nonsense claims.

Without an opening, micro or not, you would simple just be changing the internal air pressure, which would definitely not block the lens from moving.

If you want to read up on physics, this would be a good start.

I guess, you did not read my post very well !

I clearly stated, that , somewhere, on Youtube, I saw a clip of a camera being activated in a smoke filled box, that showed how an extending lens , sucked outside air, into the body.

Unfortunately I did not bookmark the page, otherwise I could have posted it here.  Never thought I would need it !

It was to do with an owner of a ??  G10 ? complaining about dust on his sensor, and  ? Canon ?? reluctantly honoring their guarantee !

So do not call it  NONSENSE !

As said, I cannot find the video, but i found this !

https://photographylife.com/what-to-do-with-dust-inside-lens

Now, read that ! And tell him, he is talking NONSENSE !

You might be wondering how and why lenses get dust inside. Let me explain a couple of things about lenses. Every time a lens focuses or it is zoomed in and out, it “breathes”. And no, I am not talking about the effect of lens “breathing”, when an image appears smaller or bigger when focus is adjusted – I am talking about the process of inhaling and exhaling. Lenses have to breathe, due to lens elements constantly moving inside them when focus is adjusted and/or when zooming takes place. Remember what happens with pressure inside a closed plastic container? If you try to reduce the container size, the pressure inside the container will only let you reduce it to a certain level before it pushes back. A simple concept of air pressure in physics.

Now take the same concept and apply it to lenses. What would happen if lenses were completely sealed from all sides? You would only be able to zoom in a little before the lens would force you back to its original state due to pressure, especially on lenses that extend in size. A similar thing would happen with lens focus. Hence, there was no other way for camera manufacturers to design lenses – lenses with moving lens elements must inhale and exhale air.

Look ! There goes  Chrissie....   Shot down in flames  !!!!!!!

Edited April 29, 2019 by Wally The Confused
Wrong Brand !

[Chrissie]

Wally, this is your initial claim:

On 4/3/2019 at 4:05 PM,  Wally The Confused said: 

There has to be a micro opening , otherwise the lens would not be able to move.

Even as you are backpedalling now, conceding the possibility of only a little movement, before being overwhelmed by air pressure forces, this still remains nonsense, as the undisputed forces generated by the pressure differential between inside and outside don't exceed 15 Newton on a zoom lens  with dimensions similar to a 100-400GM.

This minuscule force does not qualify as making any zoom action difficult or even impossible. Any claim to the contrary does however qualify as nonsense.

[Wally The Confused]

7 hours ago, Chrissie said:

Wally, this is your initial claim:

On 4/3/2019 at 4:05 PM,  Wally The Confused said: 

There has to be a micro opening , otherwise the lens would not be able to move.

Even as you are backpedalling now, conceding the possibility of only a little movement, before being overwhelmed by air pressure forces, this still remains nonsense, as the undisputed forces generated by the pressure differential between inside and outside don't exceed 15 Newton on a zoom lens  with dimensions similar to a 100-400GM.

This minuscule force does not qualify as making any zoom action difficult or even impossible. Any claim to the contrary does however qualify as nonsense.

Where, am I backpedalling  ? 

  I am proving you wrong, on all fronts ! 

I even have independent  reviews, from honored photographers, & scientists, to back me up !

Even people on this very forum !

Perhaps you subscribe to the scientific equation, that  proves,  Bumble Bees, cannot  fly ?

There are none so blind... As those  who will not see !

I am not wasting any more of my time, on this thread !

 

Edited April 30, 2019 by Wally The Confused

[Pieter]

16 hours ago, Chrissie said:

15 Newton on a zoom lens  with dimensions similar to a 100-400GM.

This minuscule force does not qualify as making any zoom action difficult or even impossible. Any claim to the contrary does however qualify as nonsense.

1,5kg of force is minuscule to you? Ever tried a vacuvin pump? This displaces about twice the volume of air as my 55-210 but even extending it for 1cm takes effort. I won't say impossible, but I'd have a seriously hard time extending the lens if it were creating a vacuum, let alone keeping it in place for an extended period of time. I usually respect your comments Chrissie but this one just doesn't cut it.

20 hours ago, Wally The Confused said:

What would happen if lenses were completely sealed from all sides? You would only be able to zoom in a little before the lens would force you back to its original state due to pressure, especially on lenses that extend in size. A similar thing would happen with lens focus.

You keep on foregoing my statement that intake air can be blown out the same way rather than into the camera body. As for lens focus (and non-extending zoom lenses with fixed front/rear elements): it can be done with a fully airtight lens as long as the volumes of air in front and behind of the focus group (or zoom group) are connected by a levelling vent.

Summary of the whole discussion: some (but not neccesarily all) lenses indeed pump some air into the body. The important question is: which lenses do/don't, and what about dust in the lenses? To me this seems more like a problem than sensor dust as it can't be cleaned as easily as the sensor.

Edited April 30, 2019 by Pieter
added fixed zoom lenses into the equation

[Chrissie]

3 hours ago, Pieter said:

this one just doesn't cut it

Pieter, thanks for your openness.

To give Wally the Unspeakable the benefit of any doubts possible, I took the worst of all possible assumptions. The 15 Newton resisting force would only be reached, if all of the following conditions would be met. In particular, if the sample lense:

• had a barrel diameter of 70mm
• a fully compressed length of 200mm
• a fully extended length of 280 mm
• was completely hollow inside
• had been manufactured and sealed at the fully extended (400mm) position (i.e. rendering a pressure differential of zero between inside and outside of the lens at this position).

Compressing this volume by fully zooming out (100mm position) would shrink its internal volume by 28.5%, resulting in an increase of internal pressure up to 140% of ambient pressure. So we are talking about a pressure differential of 0.4 bar, acting upon the full front surface (diameter 70mm), and this is where the 15 Newton comes from. And this is, btw, only the force acting axially, while the user would only have to apply his force to the zoom ring, which has a friction brake in itself. What I'm implying by this is, that holding this zoom lens in any position is effortless, regardless of pressure differential.

We can discuss ad nauseam whether this force is difficult to overcome or not. This of course is very much subject to everyones physical capabilities and individual perception. I'm not going into that.

But the initial claim, that 

On 4/3/2019 at 4:05 PM, Wally The Confused said:

the lens would not be able to move.

is definitely nonsense. It states in absolute terms, that regardless of the force applied, no movement would be possible. Being a mechanical engineer by education and profession, I tend to take such statements as verbatim. Having to overcome a maximum resisting force of 15 Newton just does not qualify as a blocking obstacle whatsoever.

To put this a little into perspective:

Whoever handles a Sony alpha and the 100-400GM lens combo is dealing with a combined weight (force) of 21 Newton already, and nobody in their right minds would claim, that this weight is impossible to lift. This, btw, is the factual background, against which I qualified Wally's initial claim as nonsense.

Thanks to everybody for their patience. I'm leaving the last word to whoever wants to have it. I'm not going to elaborate this any further.

 

 

 

[slackercruster]

Never a problem and have had dozens of dig cams. Turn the cam down and change lens. Or change lens quick and cam not down. Once in a while I blow off the sensor, but not very seldom. If you are in a dust storm or something OK, be worried.