Results 1 to 11 of 11

Thread: Why won’t I get same exposure from M and P with flash?

  1. #1
    Join Date
    Dec 2007
    Location
    Pacific Northwest
    Posts
    209
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Feedback Score
    2 (100%)

    Default Why won’t I get same exposure from M and P with flash?

    Can anyone explain why the P mode would expose differently with flash than the M mode???

    I carefully exposed the Manual image for dead center on the meter. The P mode exposed for 1/50 f 3.4 and the M mode exposed for 1/6 f3.4.

    Clearly one is brighter…the manual looks better to me in terms of exposure, but the Auto may be more accurate in terms of tonality at that time of the day—without flash in the room...pictures below can be view large with the images labelled...
    Last edited by martin kimeldorf; 07-25-2009 at 02:38 PM.
    Martin Kimeldorf
    If you want to make God laugh
    Tell him your plans...

  2. #2
    Join Date
    Jan 2006
    Location
    In Beautiful So-Cal
    Posts
    6,791
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Feedback Score
    20 (100%)

    Default Re: Why won’t I get same exposure from M and P with flash?

    Fill flash verse main flash?
    It looks like the M mode has a lot more ambient light than the P mode one does.

  3. #3
    Join Date
    Mar 2006
    Location
    Ayer, Massachusetts, USA
    Posts
    4,646
    Thanks
    0
    Thanked 24 Times in 21 Posts
    Feedback Score
    20 (100%)

    Cool Re: Why won’t I get same exposure from M and P with flash?

    Quote Originally Posted by martin kimeldorf View Post
    Can anyone explain why the P mode would expose differently with flash than the M mode???

    I carefully exposed the Manual image for dead center on the meter. The P mode exposed for 1/50 f 3.4 and the M mode exposed for 1/6 f3.4.

    Clearly one is brighter…the manual looks better to me in terms of exposure, but the Auto may be more accurate in terms of tonality at that time of the day—without flash in the room...pictures below can be view large with the images labelled...
    Ultimately, because the source code to the camera firmware is closed source, and Olympus engineers don't hang around the forums answering questions, we won't know why they do this or that. We can speculate about the behavior, but we can't give authoritative answers. It can be frustrating, but you often times have to treat the camera as a black box. You use it enough that you know in this case it does this, and in this other case it does that.

    I would speculate that in the auto case, the camera is trying to maximize the use of background light and minimize the use of the flash. This is actually a feature, in that if it optimized for the flash, it may leave the rest of the scene dark. The white walls also probably through off the metering.

  4. #4
    Join Date
    Feb 2008
    Location
    USA (Pittsburgh PA) and Singapore
    Posts
    561
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Feedback Score
    89 (100%)

    Default Re: Why won’t I get same exposure from M and P with flash?

    These are the notes I made from "systematic" probing of the TTL-flash logic:

    -- In Aperture Priority mode with Flash modes Auto, Fill-in or Red-eye
    - If the ambient light meters less than your selected F-number and a S-speed of 2x current lens focal length, the camera will select a S-speed of 2x focal length (hand-holding S-speed). Therefore, your chosen F-number and the camera chosen S-speed will under-expose the scene. When taking the shot, the flash will put out enough light to fill-in the missing f-stops, so that your shot is correctly exposed.
    - If the ambient light meters more than your selected F-number and a S-speed of 2x focal length, the camera will select the correctly metered S-speed. Therefore, your chosen F-number and the camera chosen S-speed will expose the scene correctly. When taking the shot, the flash will put out enough light to fill-in the shadows, but the ambient light is the main light. Watch out for a camera chosen S-speed of 1/160s, 1/180s or 1/250s, as this might be an indication the camera has hit the max flash sync-speed. You will need to go into FP Flash mode so that a higher S-speed can be chosen, otherwise the scene will be overexposed.

    -- In Aperture Priority mode with Flash modes 1st Curtain, 2nd Curtain or Red-eye 2nd Curtain
    - Given your chosen F-number, the camera will choose a S-speed to expose the scene correctly. When taking the shot, the flash will put out enough light to fill-in the shadows, but the ambient light is the main light. Again, Watch out for a camera chosen S-speed of 1/160s, 1/180s or 1/250s, as this might be an indication the camera has hit the max flash sync-speed. You will need to go into FP Flash mode so that a higher S-speed can be chosen, otherwise the scene will be overexposed.

    -- In Shutter Priority mode with all Flash modes
    - Given your chosen S-speed, the camera will choose a F-number to expose the scene correctly. When taking the shot, the flash will put out enough light to fill-in the shadows, but the ambient light is the main light.
    - If the metered F-number is less than your lens' smallest F-number, your chosen S-speed and the camera chosen F-number will under-expose the scene (F will blink in the Viewfinder). When taking the shot, the flash will put out enough light to fill-in the missing f-stops, so that your shot is correctly exposed.

    -- In Manual mode with all Flash modes
    - If your chosen F-number and S-speed expose the scene correctly, when taking the shot, the flash will put out enough light to fill-in the shadows, but the ambient light is the main light.
    - If your chosen F-number and S-speed underexpose the scene , when taking the shot, the flash will put out enough light to fill-in the missing f-stops, so that your shot is correctly exposed.

    I can see a certain pattern in the TTL logic Olympus used, and it seem consistent and useful. Comments and corrections welcomed.
    Last edited by travelfotografer; 05-13-2008 at 09:11 PM.
    Leon . . travelfotolog E-3 HLD-4 GS-3 . E-420 . E-420i . E-330 . E-1 FS-2 SHLD-2 GS-2 . 9-18 . 12-60 x2 . 14-42 . 14-50 Vario-Elmarit . 25 Summilux . 25 Pancake LH-43 . ED 40-150 . 50 . 50-200 SWD x2 . EC-14 . EC-20 . EX-25 . FL-50R x2 . FL-36R x2 . FL-BKM03 . RM-1 . RM-CB1 x2 . RM-UC1 x2 . AC-1 x2 . B+W MRC KSM. COLORMUNKI . ENELOOP . FEISOL . LENSPEN . LEXAR UDMA . LOWEPRO . MARUMI Super DHG . NEXTODI . PROSTRAP . UPSTRAP

  5. #5
    Join Date
    Sep 2005
    Location
    Sweden
    Posts
    6,393
    Thanks
    1
    Thanked 8 Times in 5 Posts
    Feedback Score
    5 (100%)

    Default Re: Why won’t I get same exposure from M and P with flash?

    Wow! Good work probing and registering the behaviour Leon.

    I have read but not yet digested your summary so I can't comment but it appears to make sense.

    Cheers, Jens.
    Motto: Wildlife won't come to me unless I go to it.
    --------------------------------------------------------
    My Wildlife Photos: jensbirch.smugmug.com

    E-5, E-3, E-510, IR-E-1 ,E-P2
    ZD: 7-14, 14-54, 50, 50-200 SWD, 90-250/2.8, 300/2.8, EC-14, EC-20
    Peleng 8mm fisheye, shift Tamron SP 17/3.5, Tokina AT-X 300/2.8
    FL-50R, FL-40, FL-20, HLD-2, HLD-4, cleaved ZD EX-25 w. electric bypass, 250D, 500D, KatzEye Plus OptiBrite
    Feisol CT-3472LV and CM-1471

  6. #6
    Join Date
    Feb 2008
    Location
    USA (Pittsburgh PA) and Singapore
    Posts
    561
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Feedback Score
    89 (100%)

    Default Re: Why won’t I get same exposure from M and P with flash?

    Jens,

    Thanks. I did this a while ago to try to make sense of the E-system TTL-flash logic. I wanted to get predictable results and Oly's infamous product documentation didn't help. I hope more forum members will check, correct and add to this.
    Leon . . travelfotolog E-3 HLD-4 GS-3 . E-420 . E-420i . E-330 . E-1 FS-2 SHLD-2 GS-2 . 9-18 . 12-60 x2 . 14-42 . 14-50 Vario-Elmarit . 25 Summilux . 25 Pancake LH-43 . ED 40-150 . 50 . 50-200 SWD x2 . EC-14 . EC-20 . EX-25 . FL-50R x2 . FL-36R x2 . FL-BKM03 . RM-1 . RM-CB1 x2 . RM-UC1 x2 . AC-1 x2 . B+W MRC KSM. COLORMUNKI . ENELOOP . FEISOL . LENSPEN . LEXAR UDMA . LOWEPRO . MARUMI Super DHG . NEXTODI . PROSTRAP . UPSTRAP

  7. #7
    Join Date
    Dec 2007
    Location
    Palo Alto, California
    Posts
    141
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Feedback Score
    4 (100%)

    Default Re: Why won’t I get same exposure from M and P with flash?

    Very useful, Leon; thanks for working it out. I've been puzzling about the TTL logic, too.

    The table "Flash Synchronization and Shutter Speed" on p. 129 of the English version of th E-3 manual is consistent with what you said, particularly the shutter speed of 1/(2 x focal length) for P and A modes. But you've gone significantly farther than the table, particularly in your analysis of how much light the flash supplies depending on whether the photo would otherwise be underexposed or adequately exposed.

    ----------------------

    Photo website: www.symbiote.smugmug.com

    E-3, E-5, E-M1
    12-60mm SWD,
    50-200mm SWD,
    ZD 50mm f/2.0, Sigma 150mm f/2.8 macro
    Panasonic/Lumix 25mm f/1.4
    Rokinon 7.5mm f/3.5 FE
    Misc OM & FD lenses
    EX-25, EC-14, EC-20, Canon 500D
    FL-36R, FL-50R, Yongnuo 560-II
    FL-BKM03 Twin Bracket

    Induro CX-213 tripod,Velbron ballhead
    Gitzo G1564L monopod




  8. #8
    Join Date
    Jan 2006
    Location
    In Beautiful So-Cal
    Posts
    6,791
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Feedback Score
    20 (100%)

    Default Re: Why won’t I get same exposure from M and P with flash?

    Very Nice write up, and an excellent explanation.

  9. #9
    Join Date
    Mar 2006
    Location
    McKinney, Texas
    Posts
    1,849
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Feedback Score
    2 (100%)

    Default Re: Why won’t I get same exposure from M and P with flash?

    Leon: What Tony and others said - thank you !

    Peter

  10. #10
    Join Date
    Aug 2006
    Location
    St. Peters, Missouri USA
    Posts
    1,111
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Feedback Score
    14 (100%)

    Default Re: Why won’t I get same exposure from M and P with flash?

    appreciate the explaination Leon,, seems to make sense but another item to try and remember about the E3,,

    Derry

  11. #11
    Join Date
    Dec 2007
    Location
    Pacific Northwest
    Posts
    209
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Feedback Score
    2 (100%)

    Question Re: Why won’t I get same exposure from M and P with flash?

    Okay...I've consulted further and came up with the following observation. I'd enjoy hearing what any of you might think further on this issue:

    I concluded based on Leon's input that In P mode the E-3/Fl50 did not expose enough for ambient, rather it under-exposed the scene so flash could be hand held choosing S = 1/fl or 1/23 x 2 1/46 (about 1/50)…which should be close to hand holding speed.

    (When I manaully exposed for the scene at max f-stop 3.4...it read 1/6 and 1/50 for ambient.)

    Since I was at max aperture for the fl (23) the P-mode could not change ISO which was fixed, and tried to add enough flash to bring the scene up from the 1/6 to the 1/50 (which it seems to prefer for hand holding).

    Now I’m guessing that it could not put out enough broad light to give me the bright scene I had in M-mode at 1/6 and 1/50.

    Do you think that is a good guess on my part?

    (This seems to explains why so many people I talk to use Manual instead of P mode.)

    However, the Manual was dependent on having a tripod. Alas.

    HERE ARE MY TWO FURTHER QUESTIONS
    1) Is my assumption that FL50 could not put out enough light and so left it under-exposed looking in the P-mode?

    2) If you found yourself without a tripod...what might you have done?
    Martin Kimeldorf
    If you want to make God laugh
    Tell him your plans...

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •