Possibly embarassing newbie question: defective camera or misunderstanding

Discussion in 'Photography Beginners' Forum' started by AlbertoDeRoma, Dec 9, 2009.

  1. AlbertoDeRoma

    AlbertoDeRoma TPF Noob!

    Joined:
    Nov 26, 2009
    Messages:
    71
    Likes Received:
    1
    Location:
    San Francisco Bay Area
    Can others edit my Photos:
    Photos OK to edit
    Hopefully the newbie forum is OK for asking potentially embarrassing questions :confused:.

    I have 2 "beginner" cameras:

    1) A Leica (Panasonic) D-Lux 4
    2) A Panasonic FZ35

    I love the D-Lux 4, but I missed having a zoom for certain types of pictures so, after reading many positive reviews, I bought the FZ35.

    I took the FZ35 out for a "shoot" today and I was surprised to see how slow the shutter speeds had to be in order to get the correct exposure all the shots. The FZ35 was on average 2 stops "slower" than the D-Lux 4 - even when I wasn't taking advantage of the zoom. So when I went home I used both cameras to make a more controlled comparison.

    Even when I set the aperture on both cameras to the same value (i.e. 2.8) and use the same ISO (say 200) and don't use any zoom on either (i.e. 1x), the FZ35 requires a considerably slower shutter speed to take the exact same shot (no flash.)

    Here are some actual readings I just took (indoor) for the same exact picture with the two cameras:

    D-Lux 4: f2.8 1/8 ISO200
    FZ35: f2.8 1/2 ISO200

    This difference (i.e. two stops) carries to other lighting conditions (e.g. 1/100 for the D-Lux and a sloooow 1/25 for the FZ35 for an outdoor shot.)

    Does this sound right? Everything seems to be working on the FZ35, and I like everything about this camera except for this big difference between it and the D-Lux 4. Is it possible that the FZ35 is this much "slower" (sorry if that's not the right term) even though I am using the same aperture and ISOs?

    Any explanations would be greatly appreciated.

    Thanks a bunch,

    Alberto
     
  2. Inst!nct

    Inst!nct TPF Noob!

    Joined:
    Sep 16, 2009
    Messages:
    702
    Likes Received:
    1
    Location:
    Troll, Wisconsin
    Can others edit my Photos:
    Photos OK to edit
    I havent looked up the lens on those things, im guessing they are p&s? but if its a PnS, if its optical, problem is youre shooting at different zooms, and if you have a dslr, check the length of your lens and compare the (cant find the word atm, like 55mm, idk) but yea
     
  3. KmH

    KmH Helping photographers learn to fish Supporting Member

    Joined:
    Apr 9, 2009
    Messages:
    38,225
    Likes Received:
    5,003
    Location:
    Iowa
    Can others edit my Photos:
    Photos OK to edit
    They are only comparable at f/2.8 if they are both at the same focal length.

    To keep the math simple: A 100 mm lens with an aperture setting of f/4 will have a lens opening of 25 mm. A 135 mm lens with a setting of f/4 will have a pupil lens opening of about 33.8 mm.
     
  4. Derrel

    Derrel Mr. Rain Cloud

    Joined:
    Jul 23, 2009
    Messages:
    35,456
    Likes Received:
    12,795
    Location:
    USA
    Can others edit my Photos:
    Photos OK to edit
    Does the Panny have optical image stabilization? I was thinking if it did, maybe the manufacturer favored a slower exposure, which the OS could help alleviate shake issues with. But yeah--I understand your issue totally--a 1/100 second speed is "okay", but 1/25 second is potentially disastrous on a wide,wide range of outdoor subjects.

    Not being familiar with either camera, my comments are only suppositions, but one thing I might say is that I think the Leica D-Lux 4 is aimed more at the street shooter/candid market, while the Panny is aimed at a different type of shooter; back in the 80's and 90's, a similar situation existed with Programmed Auto cameras and Point and Shoots; they took GREAT PHOTOS indoors in Programmed auto modes, but only IF the camera was on a tripod! Speeds like 1/4 second at f/8 at ISO 200 would give nice depth of field for interiors of churches, landmarks, etc, but produced beautifully exposed smears in candid shooting due to slow shutter speeds; the Panasonic's current settings seem slanted toward a very slow shutter speed, which is indicative of a different *actual ISO* than the D-Lux has *if* the exposures you list give the same density in exposures.

    One small "trick" manufacturers were doing a few years ago was incorrectly stating the ISO settings, which lead to better reviews of the cameras in terms of noise-per-ISO setting; not saying that's what Panasonic did when they engineered the Leica D-Lux 4 (it is a Panasonic with a Leica badge), but obviously, there's something odd at play; is the Panasonic camera set to an exposure compensation mode? Does it have shiftable programmed mode?
    Do the exposures have *identical* density, despite the difference in exposure settings? IS one camera set to say a semi-spot metering mode, the other to an evaluative mode?

    One of the simplest ideas would be to compare shots from each camera, of the same,exact scene, to see which one has the higher density exposure, or the more-bright exposure, and then adjust the ISO on the other camera upward to see if you can get a result that is still acceptable on (this is a guess--on the Panasonic???) the other camera.
     
  5. AlbertoDeRoma

    AlbertoDeRoma TPF Noob!

    Joined:
    Nov 26, 2009
    Messages:
    71
    Likes Received:
    1
    Location:
    San Francisco Bay Area
    Can others edit my Photos:
    Photos OK to edit
    Thanks KmH,

    Here are the specs for the FZ35:

    Zoom wide (W) 27 mm
    Zoom tele (T) 486 mm (18 x)
    Aperture range F2.8 - F4.4

    And here are the specs for the D-Lux4:

    Zoom wide (W) 24 mm
    Zoom tele (T) 60 mm (2.5 x)
    Aperture range F2.0 - F2.8

    By using the W number, I get:

    FZ35: 27/2.8 = 9.6mm
    D-Lux 4: 24/2.0 = 12.0mm

    Am I using the right numbers?

    If that's the case, the D-Lux opening is 12.0mm and the FZ35 is 9.6mm (i.e. smaller opening) - which *is* smaller, but is that smaller enough to explain a 2-stop difference?

    Thanks.
     
  6. Dwig

    Dwig TPF Noob!

    Joined:
    Mar 11, 2009
    Messages:
    1,261
    Likes Received:
    0
    Location:
    Key West FL
    Can others edit my Photos:
    Photos NOT OK to edit
    KmH is incorrect in that the absolute aperture (diameter of the exit pupil) is not a factor in exposure. The metric that is related to exposure is in theory the "focal ratio" or "f/stop", the aperture relative to the focal length. In practice there are additional factors that influence the effective transmission of a complex lens that cause the brightness of the image to vary between lenses of the same f/stop. The metric that includes a correction for transmission is the T/stop.

    The OP's original test is valid if, and only if, the comparison pictures were taken at each camera's widest focal length, taken of very distant subjects, the ISOs were set manually, and were processed into JPEGs using very similar settings. If the RAW to JPEG conversion took place in camera, as is normal with this class of camera, the cameras need to be set to as similar a set of settings (brightness, contrast, saturation, ...) as possible.

    Assuming that the OPs test was performed correctly there appears to be several possible reasons for the difference in settings:

    1. Round-off error: f/stop and shutter speed info is not displayed with 100% accuracy in any camera. f/stops are usually rounded off to the nearest 1/3 or 1/2 stop increment though P&S cameras sometimes only display full stop increments. Shutter speeds in P&S cameras are often displayed in only full stop increments. If the lenses were wide open so that they both were theoretically at f/2.8 the actual shutter speeds could be as close as 1 1/3 stop and still result in the seemingly 2 stop difference,

    2. T/stops: complex zoom lenses can be as much as one stop "slower" than their f/stop indicates although a 1/2 stop discrepancy is more likely. Still this could easily account for around a 1/2 stop difference between two f/2.8 lenses. In fact, lenses made for the cinema industry are usually marked in precisely measured T/stops since it is so critical that scene to scene exposures match.

    3. ISO Calibration accuracy: calibrating ISO speed for digital sensors is difficult. There are standards, but many camera manufacturers deviate somewhat to get image files they think look right. It is common to see two cameras with as much as a stop difference in actual sensitivity at the same marked ISO. ISO 200 on one camera isn't the same as ISO 200 on another. Check out DXOmark.com for some carefully done sensor tests. BTW, these are the only noise tests that I've every seen that are valid as they compare noise at actual measured ISOs rather than manufacturer's often elevated ISO markings.

    4. F/stop calibration accuracy: Its perfectly normal for there to be 1/6 stop difference between the actual f/stop and the marked f/stop. f/stops are not usually marked in increments smaller than 1/3 stop. Max aperture is almost always rounded off to the nearest 1/3 stop increment. Its not uncommon for lenses to show even larger "inaccuracies" due to manufacturer's bravado.

    5. light fall off: No lens delivers perfectly even illumination across the whole image. Better lenses are more even. One f/2.8 lens may yield the brightness expected of f/2.8 in the center but be 1-2 stops dimmer at the edges while another looses only 1/2 stop. The result is that even though they both produce identical brightness at a spot in the center the later lens yields more light over the image on average. In such cases, the more even lens will cause the metering system to use a higher shutter speed (all else being equal).

    It would take only moderate and normal differences in several of these points combined to account for the displayed exposure difference in the OPs two cameras. In fact, display roundoff and light fall off together are sufficient. Add a slight difference in ISO calibration and its easy to see how this can happen without any intentional overly zealous calibration of f/stop or ISO on the part of one manufacturer or any fault in a particular camera. Actually, if the images look properly exposed there is no reason to accuse either camera of being "defective" (e.g. not up to design and manufacturing target specifications or quality).
     
  7. AlbertoDeRoma

    AlbertoDeRoma TPF Noob!

    Joined:
    Nov 26, 2009
    Messages:
    71
    Likes Received:
    1
    Location:
    San Francisco Bay Area
    Can others edit my Photos:
    Photos OK to edit
    Dwig,

    Thank you very much for an extremely thorough and illuminating reply and explanation.

    After reading your explanation (and numerous other posts on similar issues,) I believe that my major newbie mistake was to assume that there would be much more consistency and accuracy in the way lenses+cameras are rated/labelled in terms of f/stop, ISOs, etc. I now realize that camera specs are much like audio components specs (I know much more about audio than photography at this point) where one manufacturer's spec of 200W/channel or 90db speaker efficiency rating should always be taken with a large grain of salt.

    When you add potential errors from my somewhat controlled -- but still far from test-lab standard -- test shot data with the accumulated f/stop errors you mention, it's easy to see how things can easily add up to a couple of stops.

    Thanks a bunch again for this quick lesson,

    Alberto

    P.S. As an experienced audiophile and newbie photographer, I am finding an increasing number of similarities between the two hobbies. The debate between digital and analog, discussions over specs, some people who focus more on the technical aspects of the hobby, while others are more focused on the artistic aspects, etc.
     
  8. BoblyBill

    BoblyBill TPF Noob!

    Joined:
    Oct 30, 2006
    Messages:
    2,860
    Likes Received:
    36
    Location:
    in the eye of a tornado
    Can others edit my Photos:
    Photos OK to edit
    LOL... you sir have nailed that one on the head.
     

Share This Page