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Thread: DSLR low light focusing accuracy...

  1. #1

    Default DSLR low light focusing accuracy...

    Hi People,

    I am looking for a new DSLR body. Budget is around 2.5k-3k.

    I just sold my minolta 7D reason being that the focusing is kind of hit and miss affair. Before that I had a D70 which is much more accurate in the focusing, IMHO. (maybe it is me) I chose the 7D for the anti shake so I can have a 20mm f1.8 lens with image stabilization.

    After my honeymoon, I find a lot of my pics at low light is OOF even after the camera has locked focus. Maybe it is the photographer but I have since sold the 7D and now looking for a new body.

    Is the canon 20D focusing under low light much better than the 350D and D70? How about S3 pro?

  2. #2

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    wah....i dont think the 7D is that bad...you may want to relook your technique...buying a 1Dmk2 or a D2X is not going to help if its your technique thats the issue....

  3. #3
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    in low light, almost no cameras can focus properly without any additional aid, you'll need the af assist. for the 20D it fires the flash as AF assist which can be distracting, D70 has the af assist lamp, or if you have the sb800 it illuminates the area with red lines which helps to focus even on featureless walls/paper which is the best option.

    With the 20D, the darkest I have tried focussing is in karaoke rooms where the light is just barely enough to see your face.
    “How fortunate for leaders that men do not think.” - Adolf Hitler

  4. #4

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    with the AF assist from the 580 or 550, the 20D (like all eos cameras) focusses spot on in pitch darkness.

  5. #5

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    Quote Originally Posted by yanyewkay
    With the 20D, the darkest I have tried focussing is in karaoke rooms where the light is just barely enough to see your face.
    hahaha, depending on the type of karaoke you were in, why not post some pics? hahahaha!

  6. #6

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    The 7D is actually more accurate than the D70 in low light, it has a double-cross sensor in the center which is very accurate. However, its main difficulty is that the AF sensors are very small. Good for precise focusing in good light, but hard to use in lowlight.

    This is because in lowlight, you need to find an edge contrast to get a good lock and the sensors are too small to position over an edge properly. However, if you are able to find an edge with the sensor it usually works pretty well.

    The D70 although having less sensitivity has a larger sensor which easily detects multiple edges whereever you point.
    Thus the D70 is somewhat easier to use, but I sometimes do wish for a smaller sensor like the 7D when precision is needed.


    Also, were you comparing the same class of lenses with each camera? e.g f5.6 vs f5.6 or f2.8 vs f2.8? Lenses make a big difference.
    I found the 28-75f2.8 to perform better on the 7D than on the D70 in lowlight.
    Last edited by Zerstorer; 23rd July 2005 at 09:18 AM. Reason: Key statements emphasized in bold

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    1D mkII has soo many focussing points that it is almost impossible to miss focussing.. i was once 'suaned' that if it is still OOF it is user problem already.
    “How fortunate for leaders that men do not think.” - Adolf Hitler

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    Quote Originally Posted by GitS
    hahaha, depending on the type of karaoke you were in, why not post some pics? hahahaha!
    definitely not the type which features your avatar
    “How fortunate for leaders that men do not think.” - Adolf Hitler

  9. #9

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    You need a fast lens and ensure the shutter speed is not slower than 1/focal length sec.

    So far my old D60 has such slow AF in poor lighting. But I believe minolta 7D do not have such issue.
    See my Photo Gallery at the Clubsnap

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    megaweb... i think the D7D, being a user here... does have slow focusing on some lens... esp in low light condition... slow to a crawl...
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  11. #11
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    U may want to adjust your focus technique, try to aim for something with a "contrast", eg the line between the door and the wall, the eye- the white and the black portion, etc.

  12. #12

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    Quote Originally Posted by Del_CtrlnoAlt
    megaweb... i think the D7D, being a user here... does have slow focusing on some lens... esp in low light condition... slow to a crawl...
    that is quite bad. I tried 300D with 35mm f2 and 85mm f1.8, the AF focusing is good.
    See my Photo Gallery at the Clubsnap

  13. #13

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    Quote Originally Posted by Del_CtrlnoAlt
    megaweb... i think the D7D, being a user here... does have slow focusing on some lens... esp in low light condition... slow to a crawl...
    Lens and focusing technique plays a part. Do note that the D7/D7D focus is as good as a F100/F5 in my experience. Minolta cameras have never been poor performers in lowlight.

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    Quote Originally Posted by Zerstorer
    Lens and focusing technique plays a part. Do note that the D7/D7D focus is as good as a F100/F5 in my experience. Minolta cameras have never been poor performers in lowlight.
    thats y i say some lens mah... actually i shouldn't say slow to crawl... focusing still fast... but it goes front & back, front & back, cannot lock...

    i'd say primes are sure fast no fight, like 50mm 1.7 or 1.4, sure spot on, if you have lens that are beyond f2.8, use in wedding, confirm die case...
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  15. #15

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    Quote Originally Posted by Zerstorer
    The 7D is actually more accurate than the D70 in low light, it has a double-cross sensor in the center which is very accurate. However, its main difficulty is that the AF sensors are very small. Good for precise focusing in good light, but hard to use in lowlight.

    This is because in lowlight, you need to find an edge contrast to get a good lock and the sensors are too small to position over an edge properly. However, if you are able to find an edge with the sensor it usually works pretty well.

    The D70 although having less sensitivity has a larger sensor which easily detects multiple edges whereever you point.
    Thus the D70 is somewhat easier to use, but I sometimes do wish for a smaller sensor like the 7D when precision is needed.

    Also, were you comparing the same class of lenses with each camera? e.g f5.6 vs f5.6 or f2.8 vs f2.8? Lenses make a big difference.
    I found the 28-75f2.8 to perform better on the 7D than on the D70 in lowlight.
    Being both a former 7D and D70 user, I feel the 7D sensor seems to be larger than the D70... But the center 7D sensor can lock focus in very low light with my f2.8/f1.8 lens but err.. sometimes not accurate. I rather it takes LONGER to lock with a higher accuracy than it locks focus very fast but not accurate.

    Ya maybe you are right in that the 7D is better than the D70 as I could never shoot in low light condition with the D70 kit as I could with my 7D and 20mm f1.8 lens. Can could get decent shots at a Bar in Brussels without flash with my 7D.... I am starting to miss my 7D already

    Ok so lets say I am looking for a body with "better" AF than the 7D. Is 20D better? but f2.8 zoom lens is so expensive for Canon. I read that the 20D AF is more accurate with f2.8 and better lens. Does that applies to third party f2.8 lens?

  16. #16

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    Astin gave good advice.

    try to "lock on" something that has a contrast like maybe a black design on a white teeshirt or such.

    think may sound silly but i sometimes use a torch to shine a beam at the target. (mainly for night shoots of plants and spiders)

    remember to turn on your AF assist beam (if the cam got one)

  17. #17

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    The 7D sensors are smaller than the D70. I'm very certain of it coz I've handled all the cameras I mentioned and have tested in lowlight.

    One thing you have to note is that AF accuracy for wide angle lenses in low light can be a hit or miss affair sometimes. It is not 100% accurate. It is actually far harder to achieve accurate focus with a wide compared to a tele which gives greater de-focus contrast.

    I've not tried a 20D enough to make any statement, but I can dare say that a 7D>D70>10D in low light if you are using the same type of lenses.

    Do note that traditionally, canon has lagged in the low light AF department. i.e their camera AF is specified at (20D)-0.5EV compared to -1EV for minolta and nikon. Whether this translates into actual relevance in realtime use is up to you to find out.

    In low light shooting without flash, most people resort to using primes that are faster than f2.8. f2.8 zooms can also work if you can find a edge and there isn't much difference between 1st party or 3rd party as long as the lens can transmit sufficient contrast.

    Do test out the cameras concerned with the same type of lenses before you proceed on your purchase.

    Good luck in your search.

  18. #18

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    the user manual states that so long any lens with f2.8 or faster is used, the camera executes its higher-precision AF points for focussing, hence it is independent of lens manufacturer.

    Quote Originally Posted by wind30
    Being both a former 7D and D70 user, I feel the 7D sensor seems to be larger than the D70... But the center 7D sensor can lock focus in very low light with my f2.8/f1.8 lens but err.. sometimes not accurate. I rather it takes LONGER to lock with a higher accuracy than it locks focus very fast but not accurate.

    Ya maybe you are right in that the 7D is better than the D70 as I could never shoot in low light condition with the D70 kit as I could with my 7D and 20mm f1.8 lens. Can could get decent shots at a Bar in Brussels without flash with my 7D.... I am starting to miss my 7D already

    Ok so lets say I am looking for a body with "better" AF than the 7D. Is 20D better? but f2.8 zoom lens is so expensive for Canon. I read that the 20D AF is more accurate with f2.8 and better lens. Does that applies to third party f2.8 lens?

  19. #19

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    if you're shooting with a shallow dof and using focus and recompose, that will also account for your OOF issues.

  20. #20
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    Quote Originally Posted by Astin
    U may want to adjust your focus technique, try to aim for something with a "contrast", eg the line between the door and the wall, the eye- the white and the black portion, etc.
    When its too dark, you can ask your subjects to flick a lighter or hold s tea-candle, then focus on the flame. Then while half-press, they can remove those stuff... then shoot. Also helps u visualize the framing.

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