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  #1  
Old 27th February 2020, 04:10 PM
Svend Svend is offline
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Default Effect of "cleaning marks"

I was about to pull the trigger on purchase of a 24mm lens to use on my Pentax MX, but am now hesitating after the seller has told me the front element is covered in micro-fine scratches, AKA "cleaning marks". He says these are only visible using a magnifying glass. A picture he sent of the lens shows nothing apparent on my PC screen.

Question is how much do such very fine scratches affect image quality? My understanding is they may cause loss in contrast and flare. But how bad do they have to be before this is noticeable? Can this be countered using a good lens hood? Would resolution be reduced?

I would be interested to hear the experience of others with this.

Thanks in advance!
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Old 27th February 2020, 05:22 PM
Mike O'Pray Mike O'Pray is offline
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Must have been a disappointment to learn of this, Svend, when on the point of purchase. I think our problem will be that of judging the severity of the marks in order to make an informed judgement unless we can see them and until you see the lens yourself then frankly no-one, not even you, can know if photos of the lens shows nothing

Is it possible to ask to see examples of darkroom prints from the seller that have been taken with the lens in question.

If the seller has no pics to show but he has been honest enough to admit to marks so will that person agree to a money back guarantee if on using the lens problems arise with the quality of the prints?

In the long run this may be the best guarantee that you do not buy a product that fails to meet requirements

Mike
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Old 27th February 2020, 05:25 PM
alexmuir alexmuir is offline
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Hi Svend.
Regardless of the popular line from sellers that such things ‘ have no effect on image quality, I find it hard to imagine that they don’t. The question really is how much does it bother you? I would try to avoid anything with an obvious issue, unless it was either a really good price, or hard to find another one. After all, if you decided to re-sell at some future point, you have the hassle of declaring and explaining the defect. I would have thought that suitable 24mm lenses in this fitting are plentiful, and perhaps not that expensive. I don’t use Pentax equipment, but the PK mount cameras were very popular for a long period. If you’re hesitant, I’d wait for a better example to come along.
Alex


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Old 27th February 2020, 05:31 PM
Richard Gould Richard Gould is offline
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Depends on how bad they are, I had a lens on a Retina that was badly marked with micro scratchs and the effect was not only a loss of contrast but a very soft focus effect, others have had a few marks and were fine, The retina was bought from a dealer and I got my money back, but these micro scratches, ifbad, ca completely ruin a lens, so I would personally stay away, unless it was very cheap, after all there are a lot of pentax lenses around, so one in superb condition should not be hard to find,
Richard
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Old 27th February 2020, 06:54 PM
Svend Svend is offline
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Guys - thanks for the replies. The seller is local (only an hour drive) so I will go and see the lens this weekend to check it out for myself. He has offered to discount the price quite a bit, so if the marks are minor I may go for it just to try it out. Low risk buy. I have a Pentax K5ii dslr which I could bring with me to do a few test shots, but I question whether that would tell me much given the small screen and limited zoom factor on the rear screen.

Alex, Richard - surprisingly there are very few good quality 24mm primes available for PK mount here. Pretty much none in my area except the one in question, and only a few in N. America on ebay, with most of the latter listed for ridiculous asking prices.

Richard - how bad was the Retina lens you had? Were the scratches visible without a magnifier?

Mike - good suggestion re. return guarantee. I will ask about that.
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Old 27th February 2020, 07:14 PM
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GoodOldNorm GoodOldNorm is offline
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The cleaning marks give you a good lever to bring down the price. If I was buying the lens to use and abuse I would not be concerned about very light scratches. I have a lens with a 3mm long scratch in it 1 mm deep right in the centre of the lens. I filled the scratch with black india ink and compared it to another lens without a scratch, no flare not even when facing the sun. If you have an old uv filter scratch it with wire wool and put it on a good lens and take some photographs and compare them to photographs taken without the scratched filter. See if you can tell a difference on actual prints. That will answer your question. If you want to buy the lens use it for a while then sell it on, buy a mint lens.
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Old 27th February 2020, 07:22 PM
John King John King is offline
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Default Micro scratches

For normal picture taking there would probably be very little difference, it would be only when you took pictures against the light, the flare would make the contrast drop out of the bottom of the barrel.
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Old 27th February 2020, 07:26 PM
Mike O'Pray Mike O'Pray is offline
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Svend a quick look at one of our sponsors called SDS does not reveal any 24mm lenses in either Pentax or Nikon but quite a few 28mm. I think that the 24mm is a much rarer beast. The great advantage of the 24mm is that it is about the shortest focal length that doesn't distort the picture except in those scenes where a door frame or an object with similar long straight lines is really prominent.

I have a Pentax 28mm and it is fine for almost all of my shots but if shots in very confined spaces were my speciality I'd certainly choose a 24 over a 28

A great indoors group lens. At f8 anything from about 3.5 ft to 24 ft is in focus and with a 400/800 film or faster in b&w shots with existing light, be that daylight or household lighting, are perfectly possible without flash. However I have strayed far enough from the topic at hand.

Mike
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Old 27th February 2020, 07:49 PM
Svend Svend is offline
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Norm, John - thanks for the reassurance. Makes it easier to part with a bit of cash for this. As it is the seller has dropped his price by 25% already from an already reasonable amount, so I am not worried about losing a lot on this.

Sounds like a good lens hood will be mandatory for this one. I guess we will see how it behaves shooting directly into the light.

Mike - points well taken! I am keen on the 24mm focal length for much the same reason you are. I had a Pentax M 28/2.8 but sold it -- never really took to the focal length...kind of neither here-nor-there...not wide enough to be interesting, and too wide to look natural for most landscape and nature scenes. And it didn't wow me with image quality...very blah, no depth or life...probably the only lens I have ever owned that I disliked. I have since pulled out of storage a lovely Vivitar 35/2.5 with an M42 mount that belonged to my wife's Grandmother -- what a great lens! The focal length just feels "right" to my eye, and the image quality is quite excellent. But what is missing is something wider to use on the MX, hence the 24mm (which is a Tokina RMC, by the way, which has quite a good rep). Plus, a 24 would have the bonus of working like a 36mm on my K5ii crop sensor digital....nice.

I will let you know how it works out. Should be done by Saturday, either way.
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Last edited by Svend; 27th February 2020 at 07:54 PM.
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Old 27th February 2020, 08:02 PM
Richard Gould Richard Gould is offline
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Quote:
Originally Posted by Svend View Post
Guys - thanks for the replies. The seller is local (only an hour drive) so I will go and see the lens this weekend to check it out for myself. He has offered to discount the price quite a bit, so if the marks are minor I may go for it just to try it out. Low risk buy. I have a Pentax K5ii dslr which I could bring with me to do a few test shots, but I question whether that would tell me much given the small screen and limited zoom factor on the rear screen.

Alex, Richard - surprisingly there are very few good quality 24mm primes available for PK mount here. Pretty much none in my area except the one in question, and only a few in N. America on ebay, with most of the latter listed for ridiculous asking prices.

Richard - how bad was the Retina lens you had? Were the scratches visible without a magnifier?

Mike - good suggestion re. return guarantee. I will ask about that.
The retina was bad, but did not look to bad untill I developed a test film and saw the very soft results, then upon shining a torch though the lens you could see the problem, If you go to see the lens thrn my best advice is to take a torch and shine it though the lens and that will show the problem up
Richard
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