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Thread: Focus Issues

  1. #1
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    Focus Issues

    I've taken some pretty serious criticism on another thread for saying that, in my opinion, back/front focus issues are more likely to be attributable to the Camera's AF system than to the lens itself.
    I've tested all my lenses for focus issues using Tim Jackson's focus chart and the results are below; some of the lenses I no longer own but still have the focus chart. Every one of the 30 lenses was focussing accurately enough within the DOF given the inherent inaccuracies in AF systems.

    Lens,,fnumber tested,,negative and positive DOF
    Minolta AF 17-35mm f2.8/4,,f2.8,,-14mm +30mm
    Minolta AF 24mm f2.8,,f2.8,,
    Minolta AF 28mm f2.8,,f2.8,,-12mm +12mm
    Minolta AF 28-135mm f4/4.5,,f4.5,,-14mm +10mm
    Minolta AF 35-70mm f4,,f4,,-14mm +16mm
    Minolta AF 35-70mm f4,,f4,,-14mm +20mm
    Minolta AF 35-105mm f3.5/4.5,,f4.5,,-14mm +14mm
    Minolta AF 50mm f1.7,,f1.7,,-4mm + 10mm
    Minolta AF 50mm f1.7,,f4.5,,-8mm + 16mm
    Minolta AF 50mm Macro f2.8,,f2.8,,-3mm + 10mm
    Minolta AF 50mm Macro RS f2.8,,f2.8,,-12mm + 10mm
    Minolta AF 70-210mm f4,,f4,,-12mm +5mm
    Minolta AF 80-200mm f45/5.6,,f5.6,,-4mm +10mm
    Sony 70-300mm G SSM f4.5/5.6,,f5.6,,-8mm +8mm
    Minolta MC Rokkor PF 55mm f1.8,,f5.6,,-16mm +18mm
    Minolta MC Rokkor PF 58mm f1.4,,f2.8,,-12mm +8mm
    Minolta MC Rokkor HG 35mm f2.8,,f2.8,,-10mm +40mm
    Minolta MC Rokkor PG 50mm f1.4,,f5.6,,-20mm +24mm
    Minolta MC Tele Rokkor QD 135mm f3.5,,f3.5,,-14mm +6mm
    Minolta MD W-Rokkor 24mm f2.8,,f2.8,,-14mm +10mm
    Minolta MD Rokkor 50mm f1.4,,f5.6,,-12mm +18mm
    Minolta MD Rokkor 50mm f1.4,,f5.6,,-16mm +20mm
    Minolta MD 50mm f1.4,,f1.4,,-3mm +8mm
    Minolta MD 50mm f1.4,,f1.4,,-3mm +6mm
    Minolta MD 50mm f1.7,,f5.6,,-12mm +18mm
    Minolta MD Macro 50mm f3.5,,f5.6,,-18mm +22mm
    Minolta MD Macro Rokkor 100mm f2.8,,f4,,-4mm +8mm
    MD Tele Rokkor 135mm f3.5,,f3.5,,-8m +12mm
    MD Tele Rokkor-X 135mm f3.5,,f3.5,,-14m +8mm
    MD 135mm f2.8,,f5.6,,-14m +18mm

    Although this doesn't prove or otherwise my opinion of where the fault generally lies, it does show that my A700 is behaving OK. It's also a tribute to Minolta QC that 30year old lenses are still delivering the goods. I purchased my first Minolta AF Camera back in the 80's and never had an AF problem with that or subsequent Cameras. Having said that, it's true to say that we weren't "pixel peeping" in those days and now that digital resolutions are attaining the level of film, lens problems are more obvious and some lenses just don't have the resolving power for 20MP sensors. It's also true that the higher resolution sensors will show up AF system inaccuracies. These factors have highlighted problems with some Cameras and Canon seems to be more affected than most and both Canon and Nikon had to introduce "microfocus adjust" in order to cut down on warranty returns.

    It's still early days for Sony so I think it could be a useful exercise if other Sony users on this Forum tested and published their results here. It may give an insight into what's going on.

    As for the Lens/Camera question, there is plenty of talk about focus issues on the forums and most come down to user error or the AF system rather than the lens. I came across this...
    "Here's some overview of ColorFoto's lab-test on AF quality. To measure this they shoot 10 shots with AF and give the achieved contrast relative to a best manual focus result (as the benchmark). So these results can never be better than 100% and if you see a best AF value of say 80% that means that even taking 10 AF-shots the best shot of the bunch just reached 80% contrast of the MF results
    Now, what I looked first into was the 70-200mm class of lenses as the problem of inconsistent AF was haunting me with my Tamron 70-200/2.8 review. Here are the results at different focal lengths. The 1st number is the contrast of the worst AF-try, the second number the contrast of the best AF-try out of 10 shots, all measured relative to the best you can get with MF. I've marked all results below 60%.
    - Nikon 70-200/2.8 on a D300: @70mm: 82-99%, @120mm: 94-100%, @200mm: 85-99%
    - Tamron 70-200/2.8 on a 450D: @70mm:
    25-98%, @120mm: 33-83%, @200mm: 44-99%
    - Canon 70-200/2.8 on a 450D: @70mm: 83-100%, @120mm:
    24-81%, @200mm: 22-97%
    - Sigma 70-200/2.8 on a 450D: @70mm:
    27-90%, @120mm: 40-83%, @200mm: 49-96%
    - Sigma 70-200/2.8 on a D300: @70mm: 65-77%, @120mm: 99-100%, @200mm:
    58-94%
    Well, this confirms my thoughts: AF quality is swinging wildly. Even if you (safely) assume, that 20% difference in contrast is not easily visible there are many figures below the 80% mark above.


    If you want the rest it's on this page http://www.cameralabs.com/forum/view...?p=76057#76057

  2. #2
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    I like it ... fighting fire with fact. Good job!
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

    flickr & Sdi

  3. #3
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    the a900 has microadjust

  4. #4
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    i hope v5 for a700 brings microadjust. i tested my 2 BF lenses on 2 different a700 bodies in 2 different cities and the problem remains :-(
    Canon EOS 7D

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  5. #5
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    Quote Originally Posted by Peekayoh View Post
    I've taken some pretty serious criticism on another thread for saying that, in my opinion, back/front focus issues are more likely to be attributable to the Camera's AF system than to the lens itself.
    what a thn skin you have. you didnt cop criticism on that, we disagreed.

    you're also taking the discussion compeltely out of context. if elisha said that all of her lens' were BF or only had 1 lens and it was BF, i dont disagree that it could be the result of the body.

    but elisha's OP specifically said that ONE lens was BF and the rest of them were spot on. when you have that information, its a natural conclusion tht it is FAR more liekly to be the LENS that is the problem.

    les use another analogy...if you have specs appearing in your photos it could be cos there is dust on the sesnor of dust on the glass. if someones says, "i have 4 lens' and this dust only appears when i use lens A but doesnt appear when i use lens B,C,D." where would you say the most likely location of the dust was ?

    Although this doesn't prove or otherwise my opinion of where the fault generally lies, it does show that my A700 is behaving OK. It's also a tribute to Minolta QC that 30year old lenses are still delivering the goods.
    forget all those numbers and all the rest of the commentry. think about the issue rationally based on the evidence above and tell me how the cameras AF system could be the culprit in this context. dont dosge the question...answer it.

    both Canon and Nikon had to introduce "microfocus adjust" in order to cut down on warranty returns.
    what a load of complete and utter RUBBISH. they did not HAVE to introduce it at all. the chose to introduce it as a feature by which lens' can be seperately adjusted at home with no inconvenience.

    It's still early days for Sony so I think it could be a useful exercise if other Sony users on this Forum tested and published their results here. It may give an insight into what's going on.
    As for the Lens/Camera question, there is plenty of talk about focus issues on the forums and most come down to user error or the AF system rather than the lens. I came across this...
    "Here's some overview of ColorFoto's lab-test on AF quality. To measure this they shoot 10 shots with AF and give the achieved contrast relative to a best manual focus result (as the benchmark). So these results can never be better than 100% and if you see a best AF value of say 80% that means that even taking 10 AF-shots the best shot of the bunch just reached 80% contrast of the MF results
    Now, what I looked first into was the 70-200mm class of lenses as the problem of inconsistent AF was haunting me with my Tamron 70-200/2.8 review. Here are the results at different focal lengths. The 1st number is the contrast of the worst AF-try, the second number the contrast of the best AF-try out of 10 shots, all measured relative to the best you can get with MF. I've marked all results below 60%.
    - Nikon 70-200/2.8 on a D300: @70mm: 82-99%, @120mm: 94-100%, @200mm: 85-99%
    - Tamron 70-200/2.8 on a 450D: @70mm: 25-98%, @120mm: 33-83%, @200mm: 44-99%
    - Canon 70-200/2.8 on a 450D: @70mm: 83-100%, @120mm: 24-81%, @200mm: 22-97%
    - Sigma 70-200/2.8 on a 450D: @70mm: 27-90%, @120mm: 40-83%, @200mm: 49-96%
    - Sigma 70-200/2.8 on a D300: @70mm: 65-77%, @120mm: 99-100%, @200mm: 58-94%
    Well, this confirms my thoughts: AF quality is swinging wildly. Even if you (safely) assume, that 20% difference in contrast is not easily visible there are many figures below the 80% mark above.

    If you want the rest it's on this page http://www.cameralabs.com/forum/view...?p=76057#76057
    great...another numbers person. use your common snese and answer my question.
    D800e l V3 l AW1 l 16-35 l 35 l 50 l 85 l 105 l EM1 l 7.5 l 12-40 l 14 l 17 l 25 l 45 l 60 l 75
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  6. #6
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    hey why are you bringing me into this?

    i've isolated my problem. i'm just hoping for a new FW with microadjust or worst case scenario, new lenses.
    Canon EOS 7D

    flickr
    FLUIDR

  7. #7
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    Cool Just get it fixed.

    Look, you can have the lens adjusted to standards at the depot level. I have done this in the past with terrific results. If it isn't broken, it should be adjustable for a fee. Stop worrying about "micro-adjust" and just get your glass permanently adjusted. Then it should work on every camera Minolta Maxxum through the SONY A900, no problem.
    Last edited by DonSchap; 03-25-2009 at 02:49 PM.
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

    flickr & Sdi

  8. #8
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    Quote Originally Posted by DonSchap View Post
    Look, you can have the lens adjusted to standards at the depot level. I have done this in the past with terrific results. If it isn't broken, it should be adjustable for a fee. Stop worrying about "micro-adjust" and just get your glass permanently adjusted. Then it should work on every camera, no problem.
    yeah i priced it, it's between $60-90 per lens. and i have 2 lenses that need it done
    Canon EOS 7D

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  9. #9
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    There you go ... the real answer is right in front of ya! Yes, it has a price ... but what is done is DONE!

    Last December, I had my Minolta AF 28mm f/2.8 and AF 24mm f/2.8 adjusted for focus issues. I admit, they are not zooms, but I am also counting on their focal accuracy in the studio. They are PRIMO, now.
    Last edited by DonSchap; 03-25-2009 at 02:53 PM.
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

    flickr & Sdi

  10. #10
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    Quote Originally Posted by DonSchap View Post
    Look, you can have the lens adjusted to standards at the depot level. I have done this in the past with terrific results. If it isn't broken, it should be adjustable for a fee. Stop worrying about "micro-adjust" and just get your glass permanently adjusted. Then it should work on every camera Minolta Maxxum through the SONY A900, no problem.
    when sony catch up, you will be singing a very different tune Don. micro adjust is another key feature missing from the a700. when you upgrade to the new sony a800 which will prpbably have some of these missing features you'll be telling everyone who will listen how convenient and good it is to have that feature. wait and see.
    D800e l V3 l AW1 l 16-35 l 35 l 50 l 85 l 105 l EM1 l 7.5 l 12-40 l 14 l 17 l 25 l 45 l 60 l 75
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