The mirror box is not sealed from all camera systems I have seen but shutter is also in front of the sensor and is only open when you take a photo. all you can do is just blow air into the shutter box to clean it. Static swabs work the best for me.

Am I right in assuming, dust has to get into the mirror box before it gets on to the low pass filter

and can only get onto the LPF while the shutter is open

it seems the solution to preventing dust on the low pass filter, is regular cleaning of the mirror box, rather than worrying about what lens to use

or I have I, as usual, got it all wrong

vidrazor
You can't be serious. So you're saying you wouldn't carry an ideal lens for an African shoot because it's known to potentially put dust on your sensor and instead use a less than ideal lens for the African shoot because it's known not to put as much dust on the sensor?

I think some people are looking to answer for themselves what their "Ideal" lens would be by trying to understand all of the gives and takes of different lens designs. I find choosing traveling lenses a tough choice I am constantly considering weight/size vs weather conditions vs the images I am looking to create. Sometimes it is a few primes or a very compact kit with 2 small zooms or maybe I'm needing top IQ and I have to pull out the hand cart. If I know bad weather is coming, the cheap zooms stay home and I only take my "pro" glass as I know it will work the next day.

Example: Africa (dusty) Desire a 400mm lens
Choices: 80-400vr or one of the Sigma and Tamrons that also have many zooms in that range. You also have the 400mm vr or 200-400vr.

Reality check: Your budget is under $2k.

That knocks out the 400 & 200-400 but a used 70-200vr with TC comes into play.

Most people's instinct would be the 80-400vr and not a used 70-200vr with a TC that is much better sealed.

>>as an eample, if you are in Africa or going to Africa on a Safari, would it be best to carry lens X instead of lens Y, because you will get less dust on the sensor.<<

You can't be serious. So you're saying you wouldn't carry an ideal lens for an African shoot because it's known to potentially put dust on your sensor and instead use a less than ideal lens for the African shoot because it's known not to put as much dust on the sensor?

casperwb said:
However, can this thread be used as a guide as to which lens one should purchase depending on the enviroment the camera will be used in?
As an eample, if you are in Africa or going to Africa on a Safari, would it be best to carry lens X instead of lens Y, because you will get less dust on the sensor.

I agree and I think it is naive to be dismissive. If you are out for weeks on end, you don't want half of your images with dust blotches on them.

I would think as long as you stay away from telescoping zooms you would keep more dust out. There is much to be said about the higher end (usually gold ring) Nikkors being better sealed than the consumer or 3rd party zooms. I have noticed with many primes that the front element on many moves as well. I always put a filter on out of the box to help limit any opportunity.

I have also noticed that it seems that the higher range bodies get less dust in comparison to the lower ones. I have only had dust issues a couple of times over the last 3 years on my D300 and I shoot primes swapping them out regularly in windy dust laden weather all the time. A D50 and a D80 I used, had many issues with dust. Maybe there is better sealing with the higher end ones along with the anti-static shaker thing.

SkintBrit said:
That's another interesting point to me NSXType-R. All my lenses are Nikons, and all have the gasket (rubber strip) you mention. It has always interested me to know how it stops dust etc getting through to lens mount, as it appears to me to be inappropriately sized and placed to do the job.

I think it's more of a weatherproofing thing, but I guess it could help with dust too.

It certainly think it helped a bit when I brought the D40 out with the 35mm 1.8 in the snow.

NSXType-R said:
Look for AF-S lenses maybe? The focus ring isn't always moving all the time, I guess there's less chance for grit to get caught in the ring.

But definitely look for a lens with a rear gasket going around the lens mount. Not sure what the official term is. Some refer to it as an ass gasket.

That's another interesting point to me NSXType-R. All my lenses are Nikons, and all have the gasket (rubber strip) you mention. It has always interested me to know how it stops dust etc getting through to lens mount, as it appears to me to be inappropriately sized and placed to do the job.

casperwb said:
Okay.

However, can this thread be used as a guide as to which lens one should purchase depending on the enviroment the camera will be used in?

as an eample, if you are in Africa or going to Africa on a Safari, would it be best to carry lens X instead of lens Y, because you will get less dust on the sensor.

Look for AF-S lenses maybe? The focus ring isn't always moving all the time, I guess there's less chance for grit to get caught in the ring.

But definitely look for a lens with a rear gasket going around the lens mount. Not sure what the official term is. Some refer to it as an ass gasket.

Yes, buy a zoom lens that will let you switch lenses less often. PERIOD.

SquamishPhoto said:
This is such a moot point. Dust happens. Clean it. Thread over.

Okay.

However, can this thread be used as a guide as to which lens one should purchase depending on the enviroment the camera will be used in?

as an eample, if you are in Africa or going to Africa on a Safari, would it be best to carry lens X instead of lens Y, because you will get less dust on the sensor.

This is such a moot point. Dust happens. Clean it. Thread over.

Another issue: the sensor when turned on also attracts dust due to static electricity.

I'm bringing some of my post on from the thread that went a-wall. Dust and a zoom has to do with Large volume changes in air.

Separate this discussion into two completely different zooms:
1) Telescoping Zooms like the 18-200mm
and the
2) Internal Zooms like the 70-200mm.

The Telescoping zooms many times act like a plunger, it moves in and out and the volume inside the lens barrel changes significantly. It takes Speed and a large Volume change for this to happen. Some dust does get in due to this. 3rd party lenses are much more prone in my experience as Nikon does a better job sealing their lenses.

Internal Zooms lack the volume change of air that creates the suction and the subsequent push of air and dust to a sensor. To move a significant amount of dust, the whole lens casing has to move like the 18-200mm not just a couple of elements like the 70-200mm. Even with the rear element moving, there is just not enough of a volume change for any real suction to happen.

Primes are no different than Internal Zooms - they do not suck any dirt in.

Think of it like a toilet plunger. It has a cup on the end that when you push it in, it collapses and what was in the cup is pushed out. The larger the volume of the cup, the more force you have pushing out. That is like a Telescoping zoom.

Take that same plunger, cut about 2" of the ring off and drill about 20 large holes in the remainder of the cup. When you push it and the cup collapses, what volume is there passes through the holes with very little if any exerting downward into the drain. This is just like any Prime or Internal Zooms. Even if the rear element moves, it does not move enough to create a vacuum that is needed to suck or blow dust in.

Take a your lens, prime/zoom and as you focus and zoom it, put your hand at the back and see if you can feel any "wind" or "breathing" from the lens.

Like I said in the off-topic 70-200 price drop thread, it's pointless to "debate" this unless you NEVER change lenses. If you want a dust free camera then get a waterproof point & shoot.

As I said in the other thread, assuming the rear element doesn't move, I can see no way that zooming the lens can possibly leave any dust on the sensor. However if Jeri is correct and he has seen/owns lenses where the rear element is not sealed, then it would seem quite likely. However I still maintain that a zoom lens that doesn't extend can technically be completely air tight.

1. All primes move internally when they focus and therefore, and by same reasoning, also suck dust.

2. 10.5mm f/2.8 fisheye, 35mm f/1.8, 50mm f/1.4 and 50mm f/1.8 not only have internal moving parts and elements, their back elements also move when being focused. (The back element movement of the 10.5 is very little but it's there).

3. The 105mm f/2.8 macro has a fixed back element. By comparison though the 24-70mm f/2.8 also has a fixed back element. Maybe others can confirm what other primes and zooms have fixed back elements.

4. If you're the type that shoots with primes and only switch lenses once every season then you might have an advantage over the average photographer. Although the moment you start switching lenses more often, you loose any advantage you might have since you need to switch a lot more just to keep up with the range of just one zoom lens.

Changing lenses in a dusty environment is the main culprit for me.

Maybe a zoom could also suck dust off the sensor.

Well, with many zooms, the rear element moves in and out and the entire lens expands. That air has to come from somewhere, and the air flow will generally tend to increase the amount of dust that you will see. Of course, this is not to say that not using zooms will not give you dust. There is always dust in the air (unless you are in a specially filtered clean-room), and something as simple as changing lenses is all it takes for a little bit of dust to get in.

Guys

this has been mentioned in passing and there is not a thead dedicated to this topic.

it is a subject that will be of intrest, therefore the imput of members on this subject should be valuable to all.

It seems to be the opinion of some members that some zooms suck dust into the camera, and it gets onto the sensor.

This is worth investigating.

I have found dust on the sensor of my D7000, however, lately, I am not using my zooms, mostly just the 50mm f1.8 and Tokina 100mm marco, no dust on the sensor.

maybe it is the enviroment, as we are in the rainy season and there is less dust around, however I think these lenses suck less air in as they do not zoom.

let hear what you think.