K24 colour rendition
Posted 28/07/2010 - 08:06
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They are from very different eras, but there is no lack of "bite" or contrast in the SMC Pentax 24mm f2.8 lens.
My first suspicion is that the exposure may be off and the 24mm images are actually over-exposed and a little washed out. This could be caused by a lazy lens diaphragm not closing quickly enough, or by the exposure errors that may occur when using older lenses on the DSLRs.
My first suspicion is that the exposure may be off and the 24mm images are actually over-exposed and a little washed out. This could be caused by a lazy lens diaphragm not closing quickly enough, or by the exposure errors that may occur when using older lenses on the DSLRs.
Best regards, John
Posted 28/07/2010 - 08:25
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johnriley wrote:
They are from very different eras, but there is no lack of "bite" or contrast in the SMC Pentax 24mm f2.8 lens.
My first suspicion is that the exposure may be off and the 24mm images are actually over-exposed and a little washed out. This could be caused by a lazy lens diaphragm not closing quickly enough, or by the exposure errors that may occur when using older lenses on the DSLRs.
Thank you for your answer John! I have quite high expectations for the K24, having read a lot about this lens in this forum and other sites on the net. My hope is that this lens will be useful in my attempts with low light landscape photography. The lens is in very good condition, and the diaphragm action seems to be 100%. With my limited knowledge of histograms I believe that the exposure of the photo above is quite acceptable. Most probably I just need to learn how to use this lens with the K20D...They are from very different eras, but there is no lack of "bite" or contrast in the SMC Pentax 24mm f2.8 lens.
My first suspicion is that the exposure may be off and the 24mm images are actually over-exposed and a little washed out. This could be caused by a lazy lens diaphragm not closing quickly enough, or by the exposure errors that may occur when using older lenses on the DSLRs.
[IMG]http://i812.photobucket.com/albums/zz50/bjolester/Bilde2.png[/IMG]
Best regards
Bjørn
Posted 28/07/2010 - 08:36
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I have always found that older, pre-digital, lenses tend to produce lower contrast images than new lenses do.
I feel this is likely to be the result of a combination of changing fashions among photographers for what a "good" image should look like, and the higher reflectivity of digital sensors compared with film.
When they say a lens is "designed for digital" we all know it's mostly hype, but the key word is "mostly". The newer, digital optimised lenses benefit from anti-reflection coatings designed to combat reflections from the camera sensor as well as internal reflections within the lens.
such stray light as might result from uncontrolled sensor reflections could well reduce contrast (stick an uncoated UV filter on an 80-320 and take it out in the sunshine, you'll quickly see the same effect).
Thankfully I've never found it to be a problem which couldn't be addressed by a little tweaking in processing and the sharpness of the lenses is unaffected.
I feel this is likely to be the result of a combination of changing fashions among photographers for what a "good" image should look like, and the higher reflectivity of digital sensors compared with film.
When they say a lens is "designed for digital" we all know it's mostly hype, but the key word is "mostly". The newer, digital optimised lenses benefit from anti-reflection coatings designed to combat reflections from the camera sensor as well as internal reflections within the lens.
such stray light as might result from uncontrolled sensor reflections could well reduce contrast (stick an uncoated UV filter on an 80-320 and take it out in the sunshine, you'll quickly see the same effect).
Thankfully I've never found it to be a problem which couldn't be addressed by a little tweaking in processing and the sharpness of the lenses is unaffected.
you don't have to be mad to post here
but it does help
but it does help
Posted 28/07/2010 - 08:37
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It looks like a dirty lens to me, probably the rear element. Just give it a good cleaning and try again.
It should be better with a clean, but I would be surprised if it's as good as the 18-55WR (same as Mk.2) I've yet to see any old WA lens that's as good as the Mk.2 Kit Lens or even a good Mk. 1.
It should be better with a clean, but I would be surprised if it's as good as the 18-55WR (same as Mk.2) I've yet to see any old WA lens that's as good as the Mk.2 Kit Lens or even a good Mk. 1.
Half Man... Half Pentax ... Half Cucumber
Pentax K-1 + K-5 and some other stuff
Algi
Pentax K-1 + K-5 and some other stuff
Algi
Posted 28/07/2010 - 08:45
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It will however go to f/2.8, which the kit lens can't do. It's only one stop, but sometimes one stop is all you need.
you don't have to be mad to post here
but it does help
but it does help
Posted 28/07/2010 - 09:00
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Mongoose wrote:
It will however go to f/2.8, which the kit lens can't do. It's only one stop, but sometimes one stop is all you need.
If it's not sharp at f/11...... what's it going to be at f/2.8 Ha!! Ha!! It will however go to f/2.8, which the kit lens can't do. It's only one stop, but sometimes one stop is all you need.
Bjørn the Exif data is showing 35mm for shake reduction, which won't be helping. Try a shot also with no shake reduction, also try to get 1/250th sec. exposure. It's been reported here and elsewhere that the K-7 suffers from shake at around 1/125th. The K20D doesn't but just to be safe 1/250th with SR OFF would be safer.
For any lens tests you need to take the shot at least 4 times and then pick the sharpest of the 4.
Half Man... Half Pentax ... Half Cucumber
Pentax K-1 + K-5 and some other stuff
Algi
Pentax K-1 + K-5 and some other stuff
Algi
Posted 28/07/2010 - 09:33
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Algernon wrote:
Bjørn the Exif data is showing 35mm for shake reduction, which won't be helping. Try a shot also with no shake reduction, also try to get 1/250th sec. exposure. It's been reported here and elsewhere that the K-7 suffers from shake at around 1/125th. The K20D doesn't but just to be safe 1/250th with SR OFF would be safer.
For any lens tests you need to take the shot at least 4 times and then pick the sharpest of the 4.
Ooophs... I forgot to change shake reduction input when switching from my main lens, the A35-105, to the K24Bjørn the Exif data is showing 35mm for shake reduction, which won't be helping. Try a shot also with no shake reduction, also try to get 1/250th sec. exposure. It's been reported here and elsewhere that the K-7 suffers from shake at around 1/125th. The K20D doesn't but just to be safe 1/250th with SR OFF would be safer.
For any lens tests you need to take the shot at least 4 times and then pick the sharpest of the 4.
I cleaned the rear element, and then I realized that the K24 has a lot of dust inside. What now
[IMG]http://i812.photobucket.com/albums/zz50/bjolester/K24_DUST.jpg[/IMG]
Thank you for your helpful comments Algernon, Mongoose, and John!
Best regards
Bjørn
Posted 28/07/2010 - 10:47
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I'm not sure about the K 24mm but I've opened a few 50mm and a 55mm lens before now to blast dust out, it wasn't too hard. You will never get it completely dust-free unless you have a clean room, mask, hairnet, white coat, etc. I have never had a 24mm in my hands so I've no idea how it comes apart - hopefully someone else will turn up who has done so! I find a can of compressed air (air duster) very effective for this. I even managed to blast most of the dust out of a zoom without opening it up, just by putting the air duster nozzle into suitable gaps and giving it a few good squirts.
The K lenses usually produce cooler tones than the more recent glass, I always put it down to the SMC coating recipe having changed over the years.
The K lenses usually produce cooler tones than the more recent glass, I always put it down to the SMC coating recipe having changed over the years.
Matt
Shooting the Welsh Wilderness with K-m, KX, MX, ME Super and assorted lenses.
Shooting the Welsh Wilderness with K-m, KX, MX, ME Super and assorted lenses.
Posted 28/07/2010 - 10:52
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It looks like it needs stripping down and cleaning. It might not be worth it, possibly get a few quotes and weigh up the cost.
Half Man... Half Pentax ... Half Cucumber
Pentax K-1 + K-5 and some other stuff
Algi
Pentax K-1 + K-5 and some other stuff
Algi
Posted 28/07/2010 - 12:39
Link
Hi Bjorn
I have only quickly read this post as I am in a rush so I apologise if someone have already mentioned this.
I have a few old lenses and one in particular seems sometimes to have a low contrast however the contrast slider in photoshop raw converter does not really help.
Not to panic moving the black slider to the right makes the whole image come to life - have you tried this?
This works specifially for me on images using my NPS 400mm f5.9 - it may be worth a try even though the two lenses are totally different - this may help also if you reduce the exposure as well
Cheers
Stu
I have only quickly read this post as I am in a rush so I apologise if someone have already mentioned this.
I have a few old lenses and one in particular seems sometimes to have a low contrast however the contrast slider in photoshop raw converter does not really help.
Not to panic moving the black slider to the right makes the whole image come to life - have you tried this?
This works specifially for me on images using my NPS 400mm f5.9 - it may be worth a try even though the two lenses are totally different - this may help also if you reduce the exposure as well
Cheers
Stu
Posted 28/07/2010 - 17:23
Link
Dangermouse wrote:
I'm not sure about the K 24mm but I've opened a few 50mm and a 55mm lens before now to blast dust out, it wasn't too hard. You will never get it completely dust-free unless you have a clean room, mask, hairnet, white coat, etc. I have never had a 24mm in my hands so I've no idea how it comes apart - hopefully someone else will turn up who has done so! I find a can of compressed air (air duster) very effective for this. I even managed to blast most of the dust out of a zoom without opening it up, just by putting the air duster nozzle into suitable gaps and giving it a few good squirts.
The K lenses usually produce cooler tones than the more recent glass, I always put it down to the SMC coating recipe having changed over the years.
I "only" paid about GBP 45 for the K24, so I guess I will have a go at blowing the dust of the lens like you suggest. I would be very interested in getting some advice regarding disassembly of the lens (so that I can get to the optics with an air duster!I'm not sure about the K 24mm but I've opened a few 50mm and a 55mm lens before now to blast dust out, it wasn't too hard. You will never get it completely dust-free unless you have a clean room, mask, hairnet, white coat, etc. I have never had a 24mm in my hands so I've no idea how it comes apart - hopefully someone else will turn up who has done so! I find a can of compressed air (air duster) very effective for this. I even managed to blast most of the dust out of a zoom without opening it up, just by putting the air duster nozzle into suitable gaps and giving it a few good squirts.
The K lenses usually produce cooler tones than the more recent glass, I always put it down to the SMC coating recipe having changed over the years.
Thank you Matt, Algi and Stu!
Best regards
Bjørn
Posted 28/07/2010 - 18:25
Link
You could try sucking the dust out with a powerful vacuum cleaner such as a Dyson. If it doesn't shift it at first, strip a bit off and try again.
Usually the nameplate (Pentax 1:2.8 24mm etc.) just screws out via the filter thread. Rubber or Blu-Tak should hold it on a table so you can unscrew the lens.
These two pages show you how to strip a 50mm Pentax lens down.
Link
Link
Edit: Just noticed on the same website a Spotmatic with a MIRROR LOCKUP SWITCH
Usually the nameplate (Pentax 1:2.8 24mm etc.) just screws out via the filter thread. Rubber or Blu-Tak should hold it on a table so you can unscrew the lens.
These two pages show you how to strip a 50mm Pentax lens down.
Link
Link
Edit: Just noticed on the same website a Spotmatic with a MIRROR LOCKUP SWITCH
Half Man... Half Pentax ... Half Cucumber
Pentax K-1 + K-5 and some other stuff
Algi
Pentax K-1 + K-5 and some other stuff
Algi
Posted 28/07/2010 - 19:19
Link
As the links should show, generally you unscrew the finishing ring/nameplate after which you can unscrew the front element group. The dust is usually between the front and rear element groups as this space isn't airtight - the aperture operating lever goes into it.
Do not disturb the focusing helix or the infinity stop as otherwise you'll have to re-set this, which is annoying. Assuming the 24mm is basically the same design as the 50mm then you shouldn't need to. I've dealt with a couple of lenses of late (K 28-50mm with fungus and a Tokina 28mm with a dislocated focusing ring) where there was no way to avoid disturbing these parts and I really wouldn't care to open either up again!
You might want a lens spanner like this, it makes it much easier to unscrew the notched rings used to hold some lens parts in without risking slipping and damaging the glass.
I wish I could find a 24mm for £45, with or without dust! I saw one go for £60 a while ago with a declared fungus problem, I was very close to buying it but felt the price a bit daft for a lens with a fault.
Do not disturb the focusing helix or the infinity stop as otherwise you'll have to re-set this, which is annoying. Assuming the 24mm is basically the same design as the 50mm then you shouldn't need to. I've dealt with a couple of lenses of late (K 28-50mm with fungus and a Tokina 28mm with a dislocated focusing ring) where there was no way to avoid disturbing these parts and I really wouldn't care to open either up again!
You might want a lens spanner like this, it makes it much easier to unscrew the notched rings used to hold some lens parts in without risking slipping and damaging the glass.
I wish I could find a 24mm for £45, with or without dust! I saw one go for £60 a while ago with a declared fungus problem, I was very close to buying it but felt the price a bit daft for a lens with a fault.
Matt
Shooting the Welsh Wilderness with K-m, KX, MX, ME Super and assorted lenses.
Shooting the Welsh Wilderness with K-m, KX, MX, ME Super and assorted lenses.
Posted 28/07/2010 - 19:52
Link
Dangermouse wrote:
As the links should show, generally you unscrew the finishing ring/nameplate after which you can unscrew the front element group. The dust is usually between the front and rear element groups as this space isn't airtight - the aperture operating lever goes into it.
Do not disturb the focusing helix or the infinity stop as otherwise you'll have to re-set this, which is annoying. Assuming the 24mm is basically the same design as the 50mm then you shouldn't need to. I've dealt with a couple of lenses of late (K 28-50mm with fungus and a Tokina 28mm with a dislocated focusing ring) where there was no way to avoid disturbing these parts and I really wouldn't care to open either up again!
You might want a lens spanner like this, it makes it much easier to unscrew the notched rings used to hold some lens parts in without risking slipping and damaging the glass.
I wish I could find a 24mm for £45, with or without dust! I saw one go for £60 a while ago with a declared fungus problem, I was very close to buying it but felt the price a bit daft for a lens with a fault.
Doing DIY repair to a lovely little lens like the K24 feels almost like a tabu for me, but I will give it a try Hopefully I will be able to improve the condition of the lens. Thank you Matt and Algi!
As the links should show, generally you unscrew the finishing ring/nameplate after which you can unscrew the front element group. The dust is usually between the front and rear element groups as this space isn't airtight - the aperture operating lever goes into it.
Do not disturb the focusing helix or the infinity stop as otherwise you'll have to re-set this, which is annoying. Assuming the 24mm is basically the same design as the 50mm then you shouldn't need to. I've dealt with a couple of lenses of late (K 28-50mm with fungus and a Tokina 28mm with a dislocated focusing ring) where there was no way to avoid disturbing these parts and I really wouldn't care to open either up again!
You might want a lens spanner like this, it makes it much easier to unscrew the notched rings used to hold some lens parts in without risking slipping and damaging the glass.
I wish I could find a 24mm for £45, with or without dust! I saw one go for £60 a while ago with a declared fungus problem, I was very close to buying it but felt the price a bit daft for a lens with a fault.
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981 posts
16 years
Trondheim,
Norway
K24
[IMG]http://i812.photobucket.com/albums/zz50/bjolester/K24.jpg[/IMG]
18-55WR
[IMG]http://i812.photobucket.com/albums/zz50/bjolester/18_55WR.jpg[/IMG]
Best regards
Bjørn
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