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G3 Underexposing with Manual Lenses in weak light.

Discussion in 'Panasonic Cameras' started by simonz, Jul 14, 2011.

  1. simonz

    simonz Mu-43 Regular

    89
    Jul 20, 2010
    New England
    I've noticed several times that my G3 underexposes by a couple of stops when using MF lenses in weak light using aperture priority. I've experienced this on several of my legacy lenses Changing to P mode doesn't make any difference.

    My gut feeling is that the the G3 is getting into trouble while trying to lower the shutter speed into a range that would cause blurring but the firmware give an incorrect exposure reading.

    Any other G3 owners experienced this?
     
  2. G1 User

    G1 User Mu-43 Veteran

    411
    Jul 20, 2010
    I am going out with my 400mm f/5.5, and I will get back with my experienced...
    I have only used my P/20mm so far...
    The Picture in Picture is almost like a RF center spot... Love it!
     
  3. Hikari

    Hikari Mu-43 All-Pro

    Nov 26, 2010
    Are you also stopping down? The exposure system is just having a hard time. I use exposure compensation in those situations.
     
  4. zettapixel

    zettapixel Mu-43 Veteran

    470
    Aug 12, 2010
    NY
    Yep, same with E-P1. And, actually, Canon 40d too. And yes, it happens when the lens is stopped down.
    Maybe it's because I use ESP (evaluative) metering and it's confused without aperture info. Gotta try spot sometime.
     
  5. pxpaulx

    pxpaulx Mu-43 All-Pro

    Jan 19, 2010
    Midwest
    Paul
    Yep, if you're already in low light and you stop the lens down, there is hardly any light reaching the sensor. With automated lenses, they will typically stay at a wide aperture right until the photo is taken, allowing the most light in so that exposure can be accurately calculated. It is just a limitation of using manual lenses on modern cameras.

    I was curious what kind of low light we are talking...what are the final exposure settings? If it is anything but wide open aperture with shutter speeds below probably around 1/10th, you're going to run into problems.

     
  6. Wasabi Bob

    Wasabi Bob Mu-43 Top Veteran

    Have you considered ....

    If you are using a legacy lens with a lens adapter, there is no electronic communication between the lens and the body. To an extent, it is a manual operation. The camera can compensate within a certain range, but if you stop the lens way down the camera will not arbitrarily increase the exposure time, probably to avoid motion blur (as has already been stated). On the few occasions I used a legacy lens I manually set my lens F stop and adjust the shutter speed using the histogram to set my final exposure.
     
  7. dko22

    dko22 Mu-43 Regular

    163
    Jul 26, 2010
    Stuttgart, Germany
    never noticed this so I did a few tests and I'm getting the same sort of behaviour though it varies from shot to shot. But Zettapixel has already hinted at the solution which is to use spot metering --that seems to fix it as far as I can see on the GH2 at any rate. If anything there may be a slight overexposure in poor light at small aperture. But I'm certainly not complaining. I get better metering using Nikon AIS lenses with the GH2 than on the D700, not to mention much more accurate focussing. Liveview of course on Nikon DSLR's is only really usable on a tripod so you rely on the green focus light which is not too reliable.

    David
     
  8. simonz

    simonz Mu-43 Regular

    89
    Jul 20, 2010
    New England
    I only stopped the lens down to f2.8 or f4, so I don't think it's an issue of available darkness. Since it's aperture priority, the camera chooses the shutter speed, which seemed a reasonable hand held speed.

    Also of note is that the EVF shows a correct exposure (visually), but after the picture is taken the playback show a dark, 2 stop underexposure. I think there is a bug in the G3 firmware and I hope they post a software update (they give us great customer service and throw in "peaking" as Sony has done).

    I saw a post on DPReview about someone having the same problem with the G3, so others are noticing this too.
     
  9. dko22

    dko22 Mu-43 Regular

    163
    Jul 26, 2010
    Stuttgart, Germany
    Did you check with spot metering? If that is just as bad then maybe it's a specific G3 problem as I didn't get it with the G1 or GH2. Certainly just changing 1 stop should not show a perceptible change. And yes, the EVF always shows the right exposure whatever the final result is.
     
  10. Wasabi Bob

    Wasabi Bob Mu-43 Top Veteran

    Um not quite.
    With Aperture Priority you set the aperture using the camera's thumbwheel. Knowing that, the camera will calculate the shutter speed.

    1. How does the camera body know what aperture your lens is set to?
    2. Most lens adapters will require you to turn off the body to lens communication, using the "shoot w/o lens option". With that done, the body has no "real" communication with the legacy lens.

    Aperture priority was designed to work with lens that it can control the aperture, or, in the case of Four-Third lens where the body can "read" the aperture through the data connection between the body and the lens.

    I cannot honestly say that I've used many legacy lens, but the lack of communications will cause a loss of features.
     
  11. snkenai

    snkenai Mu-43 Top Veteran

    523
    Sep 5, 2010
    I use all legacy lenses with E-p1 and G1. I set mode to P and aperture on lens. camera sets shutter speed as slow as necessary, until lower limit is reached. As lens is stopped down the vf on the G1 gets darker, but exposure stays very close to accurate. On E-p1 vf stayed accurate until lower limits reached. Much better that G1's method. I do use center weighted metering. (from my old film days) I get better control of exposure. I use exposure comp as needed
     
  12. pxpaulx

    pxpaulx Mu-43 All-Pro

    Jan 19, 2010
    Midwest
    Paul
    Bob, you're off on that one, sorry! In aperture priority you set the aperture, and the camera sets the shutter speed. When using manual lenses, you are still setting the aperture...only physically, but moving the aperture ring. The camera then selects an appropriate shutter speed (since that is what aperture priority mode does - it asks the camera to conduct auto shutter setting). Manual lenses work in either A or M modes on micro 4/3 cameras!

    To the OP, every stop down of the aperture reduces the amount of light entering the camera by half. If you are in a room with a single 75w light bulb on (since you haven't specified exactly what your shooting conditions are), I would consider that to be low light. Lets say an f1.4 lens can take a picture at 1/50th in those conditions, at f1.4. Then, it could take a properly exposed photo at 1/25th at f2, 1/10th at f2.8 and 1/5th at f4. At f4, the sensor is only receiving 1/8th the amount of light that it would receive at f1.4 - that is a very significant difference. At this point, the sensor is not receiving enough light to adequately calculate a proper shutter speed.

    Once a camera does not receive enough light, it will only go down to a shutter speed at that point (this has been my perception with a number of my pentax cameras). Say it can accurately choose proper exposure at a speed of 1/5th at f2.8 - if you then set the lens to f4, it won't work properly, and will still set itself to 1/5th shutter at f4, resulting in under exposure. This is likely what is happening, it is a limitation of the camera and no firmware could ever fix it.

    I'd still like to know the camera's settings and maybe see an example of what you're trying to say, it would make diagnosis much, much easier!

    Also regarding LCD gaining up - at least on the Oly cameras you can turn this off (have to read the manual), not sure about Panasonic, but it likely is a menu option. This is a camera feature. In order to know whether you will obtain a properly exposed photo, you should add the live histogram to your viewfinder information, that will enable you to see if the camera's chosen settings will result in a properly exposed photo.

    Now, some examples!
     
  13. G1 User

    G1 User Mu-43 Veteran

    411
    Jul 20, 2010
    I have noticed with my 400mm f/5.5 at f/11 today, that all my files were very low contrast, and underexposed a bit also.. but looking at the histogram, the dark side started a bit more to the right than normal,

    [​IMG]

    I was shooting at ISO 640-1000, and on Standard Photo with -2 NR only. Raw+JPG
    So, I guess with MF lenses... pump up the saturation, and contrast for JPG, and add 2/3 stop for RAW

    with native lenses, no problem...
     
  14. Wasabi Bob

    Wasabi Bob Mu-43 Top Veteran

    Going to check

    Try this, using aperture priority take a photo. Examine the EXIF data. What aperture is listed? If a legacy lens is used, the body won't know what F stop you've set. Yes, the body will vary the shutter speed, but only within a smaller range, compared to using an MFT lens.

    I may very well be wrong. I'm going to reach out to someone I know at Panasonic's service group. I'm enjoying this discussion!
     
  15. photoSmart42

    photoSmart42 Mu-43 Top Veteran

    628
    Feb 12, 2010
    San Diego, CA
    The camera varies the shutter speed to match your EV regardless of whether or not the camera knows what aperture you're using. The camera meters based on incoming light hitting the sensor, not based on algorithms involving aperture knowledge. That's the advantage of live view. What data do you have that says the body only varies the shutter speed within a small range with legacy lenses?

    I've been shooting primarily legacy lenses on my G1/GH1 since the cameras came out, and I've never run into a metering issue because the camera didn't know what aperture the lens had.
     
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  16. Conrad

    Conrad Mu-43 Veteran

    There is no fundamental reason why the camera needs the aperture setting to figure out the shutter speed. On top of that, you have to tell the camera explicitly that it should function without lens when you want to use legacy lenses. So the camera knows it cannot set the aperture, even if, for some obscure reason, it woul need that info.

    I've had the same experience with the GF1, and I consider it a metering problem. It's one of the reasons for me not to use legacy glass.
     
  17. Wasabi Bob

    Wasabi Bob Mu-43 Top Veteran

    Follow up

    This weekend I reached out to someone I know within Panasonic's service facility. I'll share the info as soon as I get a response. Stand by.
     
  18. Diane B

    Diane B Mu-43 Regular

    44
    Nov 8, 2010
    Its also Panaasonic's philosophy it seems to not have the LCD be WYSIWYG. The LCD will gain up so that composition and focusing are easily possible in low light--do not judge exposure in low light by what you see on the LCD or EVF. You must decide based on histogram and can adjust, as stated, with EV compensation. You cannot turn this feature off in Panasonic MFTs.

    Diane B
     
  19. G1 User

    G1 User Mu-43 Veteran

    411
    Jul 20, 2010
    A blessing with shooting at small f/stops, but a cruse for others I guess.. Yes, the Histogram always the best way to adjust EV adjustments. You never know what the Manufacture did with the LCD gain for viewing pleasure.

    I find with MF lenses, a +2/3 keeps the exposure close enough to tweak in post. Since I shoot RAW, I am not that concerned with "Exact" exposure. I still want to get it pretty close though.. it makes for easier editing.
     
  20. Wasabi Bob

    Wasabi Bob Mu-43 Top Veteran

    Here's the response

    Guys, I reached out to someone I know within Panasonic's service group. My understanding was not totally correct. Here's the reply I received last night.

    "Bob, your understanding is partially correct. When using some legacy lens with the appropriate lens adapters, we have recommended using the spot mode. If the lens is set to the largest aperture it’s possible that some lens will experience some vignette in the corners. Aside from being in slightly soft focus, the corners can be slightly darker. When these areas fall within the active metering area they can result in the photo being slightly over exposed. By using spot, it would eliminate that situation.

    Regarding your understanding, since the legacy lens has no communication with the camera body, the range that the camera body can adjust the exposure via shutter speed is slightly limited. In some situations such as the low light scenario you described the camera may not be able to extend the exposure time to properly expose the image. In part this was intentional. When the lens can communicate with the camera body some logic is used to calculate the exposure while factoring in any motion within the scene. Since there is no communication, “motion logic” can’t be included, so the range of adjustment is less. This design is not limited to Panasonic, and is used in many other brands."
     
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