can back focus be fixed?
Posted 12/07/2009 - 21:57
Link
I would imagine that if it is a clear case of back focussing then it is 'not fit for purpose' and you would be entitled to a refund or replacement. How long ago did you buy it?
By the way, I thought I had the same issue with my 16-50mm until realised I had the wrong focus settings in the K20D and changed it so it would focus on the centre of the screen which is what I am used to. Inadvertently it was focusing on a point I wasn't! Once I changed the setting it was perfect. It's a beautiful lens and very sharp. I just took some snaps (literally) of a climbing rose outside my front door and it is almost as good as a prime macro, I didn't realise it could focus so close and give such great bokeh (there, I've been dying to use that word :wink
But seriously, either a product is fit for the purpose for which you bought it or it is not, but if too much time has elapsed they may try and fix it under warranty instead of a straight swap. I guess it's one of those cases where you need to know your rights under consumer law. I would be insisting on a new lens myself, but I'm just bolshy!
By the way, I thought I had the same issue with my 16-50mm until realised I had the wrong focus settings in the K20D and changed it so it would focus on the centre of the screen which is what I am used to. Inadvertently it was focusing on a point I wasn't! Once I changed the setting it was perfect. It's a beautiful lens and very sharp. I just took some snaps (literally) of a climbing rose outside my front door and it is almost as good as a prime macro, I didn't realise it could focus so close and give such great bokeh (there, I've been dying to use that word :wink
But seriously, either a product is fit for the purpose for which you bought it or it is not, but if too much time has elapsed they may try and fix it under warranty instead of a straight swap. I guess it's one of those cases where you need to know your rights under consumer law. I would be insisting on a new lens myself, but I'm just bolshy!
FILM - Pentax: LX, K2 - 24/2.8, 40/2.8, 50/1.4, 120/2.8, 80-200/4.5, 28-105mm 2.8 macro, AF 280T
DIGITAL - Nikon : D300 - 18-200mm f/3.5-5.6G IF-ED AF-S VR DX
DIGITAL - Nikon : D300 - 18-200mm f/3.5-5.6G IF-ED AF-S VR DX
Posted 12/07/2009 - 22:26
Link
I bought it less than a month ago. It took me a few weekends to make sure it was definitely back focus.
I wanted a new lens but they insisted they had none in stock.
I wanted a new lens but they insisted they had none in stock.
https://www.flickr.com/photos/_cypher/
Pentax K10D, 50, 18-55, 28-70, 100, Sigma 10-20, Tamron 18-250, 28-75
Pentax K10D, 50, 18-55, 28-70, 100, Sigma 10-20, Tamron 18-250, 28-75
Posted 12/07/2009 - 22:37
Link
surely PENTAX have them in stock to be able to give you a like for like replacement? I would insist or ask for a complete refund unless you bought it at the old price and don't want to have to hunt around for another at that price. Less than a month? If it is faulty it is not fit for purpose and you have rights you can exercise.(My 16-50mm is for sale by the way if you do end up back on the market for one, but that's not the reason I am writing this, m'lud, honest)
A few years ago I bought an Optio 60 and it drained the batteries immediately and I insisted Pentax gave me a new one. They didn't have one in stock so they gave me the next model up
A few years ago I bought an Optio 60 and it drained the batteries immediately and I insisted Pentax gave me a new one. They didn't have one in stock so they gave me the next model up
FILM - Pentax: LX, K2 - 24/2.8, 40/2.8, 50/1.4, 120/2.8, 80-200/4.5, 28-105mm 2.8 macro, AF 280T
DIGITAL - Nikon : D300 - 18-200mm f/3.5-5.6G IF-ED AF-S VR DX
DIGITAL - Nikon : D300 - 18-200mm f/3.5-5.6G IF-ED AF-S VR DX
Posted 12/07/2009 - 22:41
Link
The k10 and k20 can be adjusted for back and front focus more so on the k20.I think the k20 allows up to 20 lens adjustments and the k10 only 1.
But its not a process i've tried
But its not a process i've tried
Posted 12/07/2009 - 22:53
Link
I did buy it at the old price so I guess my options were limited. I really wanted to just swap it out as I don't know if a lens with back focus can be fixed. I have the K10 so no focus adjustments and even if I did, when I pay £450+ for a lens I want something that works. My Sigma and Tamron lenses all worked perfectly and they cost less.
https://www.flickr.com/photos/_cypher/
Pentax K10D, 50, 18-55, 28-70, 100, Sigma 10-20, Tamron 18-250, 28-75
Pentax K10D, 50, 18-55, 28-70, 100, Sigma 10-20, Tamron 18-250, 28-75
Posted 12/07/2009 - 22:59
Link
I know your frustration eric i had a sigma 18-50mm do the same.I sent it back to srs and got a credit note(my choice)from them.I later bought a DA16-45mm.
Lenses can definately be calibrated which was an option i had at the time from sigma.But i preferred to send it to srs.
Lenses can definately be calibrated which was an option i had at the time from sigma.But i preferred to send it to srs.
Posted 12/07/2009 - 23:10
Link
It is a tough one. I can't help but feel that a calibrated lens will not be as sharp as a lens that was made correctly in the first place.
I may not have minded if it was a £200-£300 lens but when you are spending nearly £500 it just doe not feel right. I want it to be the best lens in my bag. It is a shame Pentax don't feel the same way as I keep hearing about quality control issues on that lens.
I may not have minded if it was a £200-£300 lens but when you are spending nearly £500 it just doe not feel right. I want it to be the best lens in my bag. It is a shame Pentax don't feel the same way as I keep hearing about quality control issues on that lens.
https://www.flickr.com/photos/_cypher/
Pentax K10D, 50, 18-55, 28-70, 100, Sigma 10-20, Tamron 18-250, 28-75
Pentax K10D, 50, 18-55, 28-70, 100, Sigma 10-20, Tamron 18-250, 28-75
Posted 12/07/2009 - 23:40
Link
sanderscapes wrote:
Lenses can definately be calibrated which was an option i had at the time from sigma.But i preferred to send it to srs.
I wonder how though...Lenses can definately be calibrated which was an option i had at the time from sigma.But i preferred to send it to srs.
I can't see the lens paying any "active" part in the focusing.
The lens doesn't say if it is in focus or not it simply moves nothing more right?
The sensor for the autofocus works through the lens.
The mirror is semitransparent and a second mirror behind the big mirror reflects the "focus-beam" to the focus sensor in the camera and the camera let the lens move (SDM or screwdrive).
So how can the lens effect to focus?
Even got a pretty picture
1: silicium-diode from the exposure metering system
2: ocular
3: pentaprism
4: focusing screen
5: main mirror
6: auxiliary mirror
7: auto focus module SAFOX
Stefan
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
Posted 12/07/2009 - 23:48
Link
There was a wonderful link a little while back to this topic. Essentially, lenses are made to within a certain tolerance, and so are camera bodies. This gives the possibility that if a lens is at one extreme of its tolerance, and the camera body at the other, the combination will seem awful. If, however, both lens and body are at the same position within the tolerances, they will be stunning. (Can anyone supply the link to this?)
In this case, if SRS say they are out and have sent it off for adjustment, I would believe them. Not often I say that about retailers these days! If it still doesn't stand up to expectations, then ask for a replacement.
Best wishes, Kris.,
In this case, if SRS say they are out and have sent it off for adjustment, I would believe them. Not often I say that about retailers these days! If it still doesn't stand up to expectations, then ask for a replacement.
Best wishes, Kris.,
Kris Lockyear
It is an illusion that photos are made with the camera… they are made with the eye, heart and head. Henri Cartier-Bresson
Lots of film bodies, a couple of digital ones, too many lenses (mainly older glass) and a Horseman LE 5x4.
It is an illusion that photos are made with the camera… they are made with the eye, heart and head. Henri Cartier-Bresson
Lots of film bodies, a couple of digital ones, too many lenses (mainly older glass) and a Horseman LE 5x4.
Posted 12/07/2009 - 23:55
Link
Tolerance of what Kris, you got me totally lost there
Stefan
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
Posted 12/07/2009 - 23:57
Link
Womble, in case it came across like that I wasn't implying SRS were out of order. I was really saying that regardless of whether SRS have one in stock Pentax should simply swap it out on a matter of principle and good customer service. And if we're saying that Pentax UK doesn't have one in stock, now that's really something to worry about...
FILM - Pentax: LX, K2 - 24/2.8, 40/2.8, 50/1.4, 120/2.8, 80-200/4.5, 28-105mm 2.8 macro, AF 280T
DIGITAL - Nikon : D300 - 18-200mm f/3.5-5.6G IF-ED AF-S VR DX
DIGITAL - Nikon : D300 - 18-200mm f/3.5-5.6G IF-ED AF-S VR DX
Posted 13/07/2009 - 00:06
Link
Bojidar Dimitrov wrote:
"SAFOX" stands for Sensor Ability Fortifying Optical Compensating System. It has gone through four revisions, with SAFOX-I being used in the SF series AF bodies, and SAFOX-IV being used in the ZX/MZ bodies. All SAFOX-type lenses are fully compatible with all SAFOX bodies. Basically, this means that the SF, Z/PZ, and ZX/MZ bodies are all compatible with all F and FA lenses.
This system works as follows. The main mirror which is semi-transparent in the middle lets a fixed amount of light pass to a small auxiliary mirror at its back. This mirror redirects the light to a light sensitive CCD-sensor which makes a decision on whether the image is in focus, and then transmits an electrical signal to the auto focus chip. This chip calculates the required amount and direction of rotation of the AF motor. The "in focus" analysis is based on phase detection. The light rays which are deflected by the auxiliary mirror are passed through an infra-red filter and then through a lens system that splits the image in two. If the image is in focus, these two images match. If the lens is focused to far, the two images have a greater distance on the CCD line, if it is focused to narrow these two images have a shorter distance then in the ´zero´ position. Out of this image-, phase-shifting the computer calculates the number and direction of rotations for the auto focus motor. It is not possible to stop right now from a full speed focusing to the exact point. So the speed is reduced before the right focus point is reached. The computer of the camera subdivide the number of turns to reach the right focus point. A photo interrupter in the lens count the impulses and send it back to the camera. The camera compares the actual value with the rated value. A certain steps before the rated value is reached the speed of the auto focus motor is reduced. To the motto "Trust is good — control is better" the computer starts a control measuring.
Full read
A photo interrupter in the lens is the only part in the lens that plays a part in the autofocus sequence. Would that be the cause to all the trouble?"SAFOX" stands for Sensor Ability Fortifying Optical Compensating System. It has gone through four revisions, with SAFOX-I being used in the SF series AF bodies, and SAFOX-IV being used in the ZX/MZ bodies. All SAFOX-type lenses are fully compatible with all SAFOX bodies. Basically, this means that the SF, Z/PZ, and ZX/MZ bodies are all compatible with all F and FA lenses.
This system works as follows. The main mirror which is semi-transparent in the middle lets a fixed amount of light pass to a small auxiliary mirror at its back. This mirror redirects the light to a light sensitive CCD-sensor which makes a decision on whether the image is in focus, and then transmits an electrical signal to the auto focus chip. This chip calculates the required amount and direction of rotation of the AF motor. The "in focus" analysis is based on phase detection. The light rays which are deflected by the auxiliary mirror are passed through an infra-red filter and then through a lens system that splits the image in two. If the image is in focus, these two images match. If the lens is focused to far, the two images have a greater distance on the CCD line, if it is focused to narrow these two images have a shorter distance then in the ´zero´ position. Out of this image-, phase-shifting the computer calculates the number and direction of rotations for the auto focus motor. It is not possible to stop right now from a full speed focusing to the exact point. So the speed is reduced before the right focus point is reached. The computer of the camera subdivide the number of turns to reach the right focus point. A photo interrupter in the lens count the impulses and send it back to the camera. The camera compares the actual value with the rated value. A certain steps before the rated value is reached the speed of the auto focus motor is reduced. To the motto "Trust is good — control is better" the computer starts a control measuring.
Full read
Still the AF works even with M lenses giving indication when it sees it's in focus.
And as far as I know it confirms focus right?
Stefan
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
Posted 13/07/2009 - 00:55
Link
womble wrote:
There was a wonderful link a little while back to this topic. Essentially, lenses are made to within a certain tolerance, and so are camera bodies. This gives the possibility that if a lens is at one extreme of its tolerance, and the camera body at the other, the combination will seem awful. If, however, both lens and body are at the same position within the tolerances, they will be stunning. (Can anyone supply the link to this?)
In this case, if SRS say they are out and have sent it off for adjustment, I would believe them. Not often I say that about retailers these days! If it still doesn't stand up to expectations, then ask for a replacement.
Best wishes, Kris.,
I don't doubt the service SRS offer. I am just disappointed I could not just replace the lens as I am £450 out of pocket and have nothing to show for it at the moment. They think it will be back in two weeks but that was a guess so I am just waiting.There was a wonderful link a little while back to this topic. Essentially, lenses are made to within a certain tolerance, and so are camera bodies. This gives the possibility that if a lens is at one extreme of its tolerance, and the camera body at the other, the combination will seem awful. If, however, both lens and body are at the same position within the tolerances, they will be stunning. (Can anyone supply the link to this?)
In this case, if SRS say they are out and have sent it off for adjustment, I would believe them. Not often I say that about retailers these days! If it still doesn't stand up to expectations, then ask for a replacement.
Best wishes, Kris.,
My more immediate concern was whether back focus can be fixed at all. I kind of understand your tolerance point but then it sort of implies it is just pot luck to get a really sharp result as both camera and lens have to be at the same position with regards to tolerance. That does not sound good nor encouraging. I expect Pentax lenses to work in harmony with Pentax cameras bodies. I may forgive Sigma and Tamron but surely Pentax would test each lens and body before shipping it. What ever happened to quality control.
I don't know how factually correct your comments are womble but I hope it is not the case.
https://www.flickr.com/photos/_cypher/
Pentax K10D, 50, 18-55, 28-70, 100, Sigma 10-20, Tamron 18-250, 28-75
Pentax K10D, 50, 18-55, 28-70, 100, Sigma 10-20, Tamron 18-250, 28-75
Posted 13/07/2009 - 03:43
Link
Hopefully someone will find the link to the article which was about all makes of camera / lens. Good luck with it all.
Kris.
Kris.
Kris Lockyear
It is an illusion that photos are made with the camera… they are made with the eye, heart and head. Henri Cartier-Bresson
Lots of film bodies, a couple of digital ones, too many lenses (mainly older glass) and a Horseman LE 5x4.
It is an illusion that photos are made with the camera… they are made with the eye, heart and head. Henri Cartier-Bresson
Lots of film bodies, a couple of digital ones, too many lenses (mainly older glass) and a Horseman LE 5x4.
Add Comment
To leave a comment - Log in to Pentax User or create a new account.
278 posts
18 years
London,
UK
Question is, can back focus be fixed? Is the lens not just faulty? Should I be requesting a brand new lens?
Pentax K10D, 50, 18-55, 28-70, 100, Sigma 10-20, Tamron 18-250, 28-75