How much dust is too much?

I just bought a second hand lens from the auction site and it was listed as being in "very good condition".

It has arrived and does look to be in a reasonable state externally but examining the inside it looks like there is a fair amount of dust.

I managed to take a photo which illustrates it fairly well:



What do you guys think? Will this affect image quality? Should I send it back?

I'm new to SLR so I don't know how much I need to worry about this kind of thing.

I think we need a few more details:

How old is it?

What lens is it?

Have you taken any pics with it, if so does the dust affect it?

How much did it cost?

Bottom line is whether or not it was accurately described and whether or not you are happy with the images it provides.

Regards
David

yeah very good for 70's disco shots only....
enter "not as discribed"..item

Hi David

Thanks for the reply. The lens is a SMC Pentax-A 50mm F1.7 prime. Not sure of the age. It cost me £47.50 including postage.

I have taken a couple of shots with it but not in great light. I'll need to test it more properly in daylight.

The only thing is that I have never used a fast prime lens like this before so I am not sure what results to expect.

If the dust is bad will it be immediately obvious in photos? What kind of effect on the images would it have do you think?

Thanks for your help.

The Pentax-A 50mm F1.7 is a fine lens, pictures with it should be sharp and fairly contrasty. If i were you I would take some with the lens then some with another lens to provide a comparison. It should be immediately apparent if the dust is having a significant impact. I'm puzzled as to how this much dust would get into this lens as it is normally only a problem on zooms.

Regards
David

Ok thanks David. I'll give that a go and see if I can spot anything wrong with the images.

The only other lens I have is the 18-55 kit lens that came with my K-x, probably not the best comparison! Should be ok though. I can open the kit lens up a bit wider and get in close.

Am I best testing the 50mm at the widest aperture do you think?

Eddy, the kit lens is V. good, but the 50mm F1.7 should be sharper at wide apertures (try testing both at F4). 18-55mm is very contrasty though, so may display more contrast than the 50mm F1.7. The best comparison would be another 50mm F1.7, there may be some PU members near to you who could help?

Regards
David

Thanks. I'll try testing at F4. I'll be interested to see what happens. It is really odd because the lens looks totally clear from some angles but not others. My kit lens is clear though so that should be ok.

I'm beginning to think that I might send it back anyway if I can find another that isn't dusty. Not sure it is worth the worry of always wondering if I could have had a better image.

Also it really annoys me when people don't describe their bay items properly.

Depends if I can find another cheap enough though. I don't have much cash to spend on this. Just made an offer on one in the Ads section of this forum. Fingers crossed.

I'm sure that was a goldfish swimming across!

Maybe one of these would clean it up:

http://www.seapets.co.uk/products/aquarium-supplies/aquarium-ornaments/cleaners/...

If I recieved a lens with that amount of 'gak' on it I'd deffo be sending it back...

Just one other question, is the dust in it or on it? If it's only on the surface of the rear element it's easily cleaned.

Regards
David

Inside I am afraid. The outside was also dirty when it arrived but I have given it a good clean with lens cleaning fluid and a microfibre cloth.

Possibly the seller assumed that all the dirt he could see was on the outside and never knew that it was inside as well.

I wonder if it has been taken apart - not sure how so much dust could get in it otherwise, unless it's been used in a hot dusty environment like a desert or very dry country. Send it back if you can get a refund.

Regards
David

Could be. It is odd. Can't see any signs of tampering but I guess you wouldn't necessarily.

I should be able to get a refund. Clearly been badly described.

Hassle. I was really looking forward to playing with a new toy at the weekend!