| daft_biker |
| (Action Man!) |
| 30/05/2008 16:05 |
|
Anti Dust - any good?
|
Is it any good for you? It doesn't seem to do much for me as I've had dust bunnies since I got my 40D a couple of months back.
Just a gimmick for keeping up with the competetion on features and fooling people into peace of mind or is it genuinely useful? (although is worth noting I shoot a lot at really small apertures and have heard comments from other MP-E users about discovering a whole new world of dust)
| sjaszczak |
| (A Real Gentleman) |
| 30/05/2008 16:58 |
|
|
Re: Anti Dust - any good?
|
Quote:
Is it any good for you? It doesn't seem to do much for me as I've had dust bunnies since I got my 40D a couple of months back.
Just a gimmick for keeping up with the competetion on features and fooling people into peace of mind or is it genuinely useful? (although is worth noting I shoot a lot at really small apertures and have heard comments from other MP-E users about discovering a whole new world of dust)
I've not had my 40D all that long, but I haven't noticed any dusk spots yet...but then again, I don't often shoot at really small apertures.
| bench_ubbster |
| (Bench Meister) |
| 30/05/2008 17:15 |
|
|
Re: Anti Dust - any good?
|
Well, I've had my 400D for over 2 years and I've only had to give it a wet clean once. I've given it a blow job
on a few occasions, but I've had no problems.I've had the 40D since February and again no problems and both cameras do go everywhere and I change lenses very often. So, in summary I've found the anti-dust measures very effective.
| daft_biker |
| (Action Man!) |
| 30/05/2008 18:27 |
|
|
Re: Anti Dust - any good?
|
Ah but if you never really had a dust problem before how do you know it really does work?
I reckon I've as much dust in my 40D with anti dust (left at factory settings for dust) as I do in the 300D with no anti dust
| beejaybee |
| (Marvin) |
| 30/05/2008 18:40 |
|
|
Re: Anti Dust - any good?
|
Quote:
I reckon I've as much dust in my 40D with anti dust (left at factory settings for dust) as I do in the 300D with no anti dust
Hmmm ... with a 5D which I've had to wet clean a couple of times & blow out a few more times, and a 40D which I haven't had to do anything to yet, my experience is the reverse.
| bench_ubbster |
| (Bench Meister) |
| 31/05/2008 10:32 |
|
|
|
Re: Anti Dust - any good?
|
I 'spose what I really meant is that I don't let it get in the way of my enjoyment of picture taking. The cleaning process was generally part of cleaning lenses and filters and only on one occasion have I had to give the sensor a special clean.
| daft_biker |
| (Action Man!) |
| 02/06/2008 12:27 |
|
|
|
Re: Anti Dust - any good?
|
My dialup is still goosed so couldn't upload over the weekend but this is from my 2 and a bit month old 40D before I cleaned the sensor:
I don't think there's any need for a bigger pic so you can cringe at every spot of dust on there
I think the big splodges are stuff on the lens which I've also since cleaned. Pic taken at an effective f/96 BTW.I guess without the anti dust there might have been a few more specs but from what I've seen so far the Canon anti dust feature is doing next to nothing for me and was one of my reasons for upgrading
My 300D was just as dust prone as far as I can tell.
| Malcolm_Stewart |
| (Carpal \'Tunnel) |
| 02/06/2008 13:23 |
|
Re: Anti Dust - any good?
|
My latest purchase (s/h 1D MkIII) has an anti-dust feature. It may be that it got disturbed in the post on its way to me, anyway I soon noticed a distinct dust spot in the middle of my images which was not taken out by the default turn on and turn off shakes of the filter. I had to blow it out using a Giottos Major rocket blower which is far, far more effective than any other blower I have. (In my opinion, one of the few value for money photo gadgets!)
| alanS |
| (Dr Dust) |
| 02/06/2008 13:59 |
|
Re: Anti Dust - any good?
|
I took a few shots at the weekend and only one shot (at f22) showed contamination. The place where it was almost meat that removing it could have spoilt the shot but I managed.
I used to think that my 20D suffered a lot of contamination and it certainly shows up worse when using hyper focal focusing or doing a specific check for contamination but more recently I've suffered less contamination. I assume that this is possible because the mechanism is getting bedded in and less bits are coming off the moving parts?
I'm disappointed that anti dust systems (at least some of them) are not more effective. I wonder how much further forward the filter would need to be to render contamination out of focus? or if a glass plate (like the Sigma, is it?) could be an option. It'd have to be assembled and sealed well in the factory but surely more effective measures could be found? I don't know if there's room for moving the filter forward or fitting a glass plate with EF-S cameras.
| daft_biker |
| (Action Man!) |
| 02/06/2008 15:16 |
|
|
|
Re: Anti Dust - any good?
|
Quote:
I wonder how much further forward the filter would need to be to render contamination out of focus?
In the pic I posted above some of the blotches were from dust on the rear lens element...or possibly even the front element as I cleaned both and they are not there now. Either way if you stop down enough they still seem to show up as blotches...probably easier to clone out the sharp dust?
Thanks for reminding me that some dust comes from wear of moving parts so hopefully I'll get less dust spots in future. It's not like I change lenses all that often! I'll see how it goes but at the moment anti dust has dived down my list of useful features to somewhere below liveview and I've never even tried to use that yet!!
| Benchmark |
| (Is it safe?) |
| 03/06/2008 23:38 |
|
|
Re: Anti Dust - any good?
|
I find the dust reduction system on my camera is excellent.
I bought the said camera nearly four years ago, and have taken around 40,000 exposures in some extremely dusty industrial environments, often with several lens changes. I have never suffered a problem with dust in all of that time, so if the Canon system is even half as good as that on my E1 then it will be worthwhile.
If only Canon had thought of it earlier.
| daft_biker |
| (Action Man!) |
| 04/06/2008 08:11 |
|
|
|
Re: Anti Dust - any good?
|
I'll take your word for it Nigel
.I don't think kidding ourselves on that the Canon anti dust system is as effective as it needs to be will help anybody. Canon could do with raising their game IMO.
| Malcolm_Stewart |
| (Carpal \'Tunnel) |
| 04/06/2008 08:22 |
|
Re: Anti Dust - any good?
|
Quote:
...In the pic I posted above some of the blotches were from dust on the rear lens element...or possibly even the front element ...
You are joking, I hope?
If you really can see the dust on your lens elements, what happens when your lens stops down to take the picture? Do you see the image of the diaphragm? What if it covers some of the dust spots?
| beejaybee |
| (Marvin) |
| 04/06/2008 08:37 |
|
|
|
Re: Anti Dust - any good?
|
Quote:
You are joking, I hope?
If you really can see the dust on your lens elements, what happens when your lens stops down to take the picture?
He said it was taken at f/96.... The small sharp dots are obviously close to the sensor i.e. on the anti-alias filter, there are a few large diffuse blobs which cannot possibly be unless they're blobs of contaminant (water spotting) rather than dust. OTOH they look like the sort of thing I've seen when webcamming at f/30(ish) and the IR/UV blocking filter I use, which is approx. 3 cm in front of the sensor, gets slightly dusty... Dust somewhere in or on the lens, used at a very small aperture, corresponds well with the posted image.
| beejaybee |
| (Marvin) |
| 04/06/2008 08:51 |
|
|
|
Re: Anti Dust - any good?
|
Quote:
I don't know if there's room for moving the filter forward or fitting a glass plate with EF-S cameras.
It may be of some interest that Hutech produce a range of specialist filters which fit the Canon Rebel range (i.e. the three number models) - these clip into the front of the lens mount and would do a good job of keeping dust from external sources away from the sensor. I think the UIBAR is a simple UV/IR blocking filter which would have very little if any effect on the colour balance ... it is however an interference filter and the price is somewhat extortionate, £249 from the UK supplier.
Note that these front mounted filters are incompatible with EF-S lenses and some lenses designed for APS-C sensors, because the filter occupies space which the lens rear element may wish to share. There is also an impact on the closest focusing distance to some extent (minimal with tele lenses, possibly significant with wide angles) because of the optical thickness of the filter.
Also note that there is evidence that a significant amount of sensor contaminating dust appears to originate within the camera ... a front mounted filter, or a permanently mounted lens, won't stop particles of shutter blind etc. from sticking to the sensor.
| daft_biker |
| (Action Man!) |
| 04/06/2008 09:31 |
|
|
|
Re: Anti Dust - any good?
|
I haven't cleaned one surface at a time to work out where the big blotches come from but if it was a shot from a wideangle lens with raindrops on the front element I'd expect them to show in a similar way. It was a shot from the MP-E 65mm set at 5:1 and smallest aperture.
I also seem to have a bit dust* within the lens of my compact which shows smaller and sharper at the wide end than it does at the long end of the optical zoom.
* the dust looks like a bit thread from clothing FWIW
| BigAl999 |
| (newbie) |
| 04/06/2008 19:15 |
|
Re: Anti Dust - any good?
|
I know that this may be a daft question but what is the best way to find dust on the sensor, apart from using one of those sensor scopes. I have had my 300d since Jan 05 and have never noticed any dust spots on my sensor. I do tend to change lenses quite a lot as well.
Alan
| Norman |
| () |
| 04/06/2008 19:32 |
|
|
Re: Anti Dust - any good?
|
Take a photo of a plain white surface that fills the frame. Use as small an aperture as possible. You could also try a plain blue/grey sky. Any dust will show as spots/blotches.
| beejaybee |
| (Marvin) |
| 04/06/2008 19:40 |
|
|
|
Re: Anti Dust - any good?
|
Quote:
what is the best way to find dust on the sensor, apart from using one of those sensor scopes.
Stop down to minimum aperture and take a shot of a uniformly illuminated plain wall, blue sky or something similar.
| Bone_Idle |
| (Mr Maybe) |
| 05/06/2008 15:53 |
|
|
Re: Anti Dust - any good?
|
Why does stopping dows show up dust? I can see why it would if it was on the lens, but I've never understood the phsyscs/science behind it to highlight dust on the sensor?
| alanS |
| (Dr Dust) |
| 05/06/2008 16:05 |
|
Re: Anti Dust - any good?
|
Well, as far as I can gather if you have a large aperture there's plenty of room for the light to get around any obstructions so if there are any they either don't appear or appear to be fuzzy.
If you have a small aperture the light is less able to avoid the obstruction and therefore it is defined more sharply.
So, contamination may not show up at all at f1.4, may appear and be fuzzy at f11 and may be sharply defined at f18.
I often do a test at the smallest possible aperture before going out for the day and if something is sharply defined I clean it away. I find this preferable to cloning out later and risking a shot I may want to keep being ruined, although to be honest I've only ever had to delete maybe half a dozen shots because I wasn't happy with them after cloning out contamination.
| El Sid |
| (Going potty) |
| 05/06/2008 17:08 |
|
|
Re: Anti Dust - any good?
|
Quote:
Why does stopping dows show up dust? I can see why it would if it was on the lens, but I've never understood the phsyscs/science behind it to highlight dust on the sensor?
A sort of explanation...
The sharper the light source, the narrower the beam of light becomes and the less it spreads. At small apertures the light source is a very small point, the light rays are then very close to parallel and as a result any speck on the sensor either blocks them more or less totally with respect to the photo-sites underneath or doesn't affect them at all. As a result the speck appears very clean edged.
With a large aperture the light is far less parallel as the source is less of a point. As a result the dust interacts with the light much less effectively. Because the incident angle of the light is much more varied and shallow the speck casts a shadow over more photo-sites, making it appear larger than it is, while at the same time other light rays pass behind the speck reducing the intensity of the shadows. This reduces the contrast of the shadow effectively rendering it semi-transparent.
The net result of all this is that at wide apertures dust appears as a large fuzzy blob becoming a small sharp speck as aperture reduces. The greater the edge contrast the sharper it appears which is also why it's far more visible in large plain toned light areas such as sky and virtually invisible in dark and or heavily patterned areas...
I hope this explanation is slightly clearer than mud.....
| beejaybee |
| (Marvin) |
| 06/06/2008 08:12 |
|
|
|
Re: Anti Dust - any good?
|
Quote:
Why does stopping dows show up dust?
Because the front surface of the anti-alias filter is some distance ahead of the focal plane ... there's the microprism array and the Bayer filter matrix to squeeze in as well before the light reaches the actual light sensor array.
When well stopped down, dust casts a small sharp shadow because the rays of light which just miss it are almost parallel, whichever part of the lens aperture they came through. When the lens is opened up, the shadow cone becomes wider and shorter, so that the dust shadow is large and diffuse - much harder to spot by casual inspection.
| Terrywoodenpic |
| (A whiff of silicon...) |
| 09/06/2008 20:38 |
|
|
Re: Anti Dust - any good?
|
I suspect one day every lens will come with its own sealed and attached sensor that is also matched for CA, distortion and vignetting. Of course It will also need an inbuilt semi silvered mirror pellicle. for directing the image to the viewfinder. The shutter would also need to be purely solid state electronic.
| Bone_Idle |
| (Mr Maybe) |
| 25/06/2008 13:06 |
|
|
|
Re: Anti Dust - any good?
|
Thanks for the explanations, it makes sense now!