# What does dust look like?



## mitsugirly (Feb 20, 2009)

I bought a 28mm 2.8 from someone (a used minolta maXXum <---lol double x) and when it came, there are like 3 "things" on the inside of the outter lens. The only way to describe it is that they look like "sparkles" or "glitter". Is this dust? They don't come off with blowing or a soft cloth so it's definately inside the lens.

I hear people talking about  dust on the lens all the time, but I have no clue if this is what it looks like when it's inside the lens...or will it actually look like dust? Could it just be imperfections in the glass on the lens? I have no clue and I'm thinking maybe I should send it back and get a refund. I'm just afraid that it is going to effect my pictures...any ideas?


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## Overread (Feb 20, 2009)

shoot some shots and see!
from my experinces dustis most likley to appear in the bokeh of small aperture shots (like macro and landscape) so try some f16 shots and see if appears in the shots.

If it does you can have lense cleaned profesionaly, but that costs of course - might be worth investigating as the price might not be too much for you - depends on how much this lens was and how much a new copy of it would cost you


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## EOS_JD (Feb 20, 2009)

Overread said:


> shoot some shots and see!
> from my experinces dustis most likley to appear in the bokeh of small aperture shots (like macro and landscape) so try some f16 shots and see if appears in the shots.


 
Small aperture landscape shots have little to no bokeh at all? Sure macro shots even at small apertures will have some out of focus areas but with a 28mm lens that's not a macro lens......  Did you mean large aperture shots? Bokeh is usually found in large aperture shots?

I agree that the dust may appear in very small aperture shots f16 and smaller - try a shot and see.  TBH the dust is unlikely to be seen in a normal every day shot. [/quote]


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## Overread (Feb 20, 2009)

sorry - was in macro thinking mode


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## mitsugirly (Feb 20, 2009)

bokeh<--new word for me (had to look it up). So that is the fuzziness out of focus areas in the picture around the main focused subject-correct?

I haven't had time to take any pictures...my son and his fiance have been in the hospital giving birth to my granddaughter (a month early so she's a preemie and it's been very hectic around here lately).

But now that you mentioned the "bokeh"...I'm confused. I thought that when you get a lens (like the one size 28mm, 55mm and so on) that it was for taking completely everything in clear focus pictures. So, is there still going to be bokeh on them? I guess I must have misunderstood that then.


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## Big Mike (Feb 20, 2009)

Dust on the lens rarely show us in images unless it catches stay light...light maybe sunlight coming from the side.  Try some shots and see if it affects the images.  If it doesn't, don't worry about it.


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## Overread (Feb 20, 2009)

ignor me - I am thinking all macro and small tonight!

but any lens can show bokeh if you set the settings and the shooting conditions are right - shoot at f2.8 and focus on a person infront of you with a field behind them and you will see larger areas of out of focus shot in the background


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## dxqcanada (Feb 20, 2009)

The seller should have disclosed the particles on the inside of the lens.
This is usually metallic dust particles that have collected on the internal lens elements ... it happens.

If the particles are not that large they may not affect the light entering the lens. It is hard to say, as it will be influenced by how light enters the lens and is reflected by the particles.

The only way to clean it, would be to disassemble the lens.


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## EOS_JD (Feb 20, 2009)

mitsugirly said:


> bokeh<--new word for me (had to look it up). So that is the fuzziness out of focus areas in the picture around the main focused subject-correct?
> 
> I haven't had time to take any pictures...my son and his fiance have been in the hospital giving birth to my granddaughter (a month early so she's a preemie and it's been very hectic around here lately).
> 
> But now that you mentioned the "bokeh"...I'm confused. I thought that when you get a lens (like the one size 28mm, 55mm and so on) that it was for taking completely everything in clear focus pictures. So, is there still going to be bokeh on them? I guess I must have misunderstood that then.


 
A wider lens has less magnification than a long lens so you are correct to a point.... The 28 will have more depth of feild than a longer lens at the same subject distance.

However if you move in close to your subject and set that aperture large, you will get a lot of depth of field. Here's one at 18mm f3.5


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## EOS_JD (Feb 20, 2009)

mitsugirly said:


> But now that you mentioned the "bokeh"...I'm confused. I thought that when you get a lens (like the one size 28mm, 55mm and so on) that it was for taking completely everything in clear focus pictures. So, is there still going to be bokeh on them? I guess I must have misunderstood that then.


 
Yes you have misunderstood. Single focal length lenses are just that. They are no different to the same focal length on a zoom lens. The main difference with Prime Lenses (single focal length lenses) is that they are generally faster (large maximum apertures).

To get everything in focus you want a small aperture like f16 or smaller (f22, f32 etc)  The smaller the aperture the more depth of field (dof) you will have.

Also if you are shooting a subject the further distance from your point of focus, the more dof you will have.

Wider lenses also provide a lot of dof usually because the magnification on wide lenses is lower.

So get a wide lens, small aperture and a landscape and you'll get everything in nice sharp focus.

Use even a wide lens close up to your subject and a large aperture (as noted above) and you will still see bokeh!


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