400d dust removal no good for close-ups

[mike_dodd]

How are people finding the 400D's dust removal system? In test of the 400d I

have seen the reviewers say that the dust removal seems to be good, but none of

them have done specific tests of the dust removal system itself.

 

I would agree that the system appears to be good for normal use BUT not good for

close-ups. Comparing a 20d with 400d under similar usage the 20d gets large

chunks of dirt that I have to periodially clean off with a sensor swab, these

large chunks sometimes show up on 'normal' (e.g. f8 infinity focus) images. So

far these large chunks have not shown up on the 400d photos, probably the system

has got rid of them, so normal pictures are better with the 400d.

However in place of the large chunks of dirt is a fine covering of small chunks

of dirt which do show up on close-ups (e.g. macro lens f16+) and which cover the

whole picture area not just in single large chunks like on the 20d.

Interestingly I have not seen anything like this fine covering of small pieces

on the 20d so it could be that the dust removal system on the 400d is actually

breaking up the large pieces and scattering them everywhere across the image.

The bottom line here is that it can be easier to clean up a macro shot taken on

the 20d than on the 400d as its just one or two large chunks of dirt to be dealt

with rather than the fine scattering of particles over the whole picture area.

 

I would be very interested to hear other people's experience with using the

system for CLOSE-UPS.

[mike_smith2]

It is highly unlikley that the dust is being smashed in the way you describe,

 

What are your macro subjects?

 

Just a thought but maybe it's pollen currently entering the camera body that was not airborn at the time you used the 20D?

[m_barbu1]

I'm not sure the photo being a closeup is of issue. Instead, I think it's your high aperture. The higher the aperture, the more you can see anything that might be on the sensor. At f/2.8, I can't see any of the dust on my sensor (and consequently, I haven't cleaned it yet). My inclination is to think not that the vibration is scattering them, but that the vibration can't dislodge those tiny specs of dust, because they have insufficient mass.

[mike_dodd]

I would still like to hear from other people who have actually used the system as I describe.

The specks are unlikely to be pollen or fungal spores as its not the time of year when these are most of an issue. I did have problems with pollen once on the 20d so do know what this can be like. I do take a lot of close-ups 50, 90, 180, 65mm macro lenses and thousands of shots, most of the shots with the 400d have been invertebrates, usually f16-f22 although sometimes less to avoid diffraction issues.

[m_barbu1]

Understandable. Try taking a shot at those apertures with a normal lens, against a light, solid colored background, too.

[lester_wareham]

My understanding is the filter (where the dust collects) is at a different distance from the actual sensor in the 400d compared to pre dust removal cameras like the 20D/30D et al. I'm not sure why this is but aparantly its something to do with the anti-dust measures.

 

This might change the fstop they show up at and the apparant size of the dust that is visible.

[mike_dodd]

If anyone is in any doubt about the effect of dust the enclosed shot shows it up very nicely. Its a stacked multiple image for extra depth of field so each of the 8 pieces of dust shows up as a track rather than an individual piece. the shot was taken with a 400d (with all the 'standard' dust reduction) and a 65mm macro, it is a crop of the original shot.<div></div>

[lester_wareham]

Hi mike that example is really interesting.

 

I wonder if what is happening is the dust is settling in vibration nodes across the top of the sensor (actuly the AA filter rather than the sensor).

 

One is reminded of the science experiments at school with the dust in a vibrating tube that settles in the nodal points where the vibration standing waves cancel out.

[mike_dodd]

in response to the last comment, well no, this is a stacked image, when stacking images you often get this effect of a single piece of dirt appearing several times. so here there are just 4 or 8 (not exactly certain) pieces of dirt and each bit is repeated when the images are stacked together for increased depth of field. You need to look up stacked images to understand this fully. I show a stacked extreme close-up image of this type as this is where the dirt is extremely annoying and where the dust removal technology should have been the most effective but in practice may well be worse than useless.

[lester_wareham]

OK Mike, if you were stacking then the auto frame alignment may be causing the dust to apear to move, or were you using a tripod so this is not an issue.

 

Looks like its back to cleaning the sensor in the normal way then.

 

What about the dust mapping out function, have you tried that?

 

My expectation is that that is only effective for areas of flat tone like sky etc.