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Thread: Flash question

  1. #1

    Question Flash question

    Flash question

    last week, I shot for friends wedding with k-x + *16-50 + Sigma 610 std...
    i will set the iso to 100-400 or 100-800 f4-8 with AV mode
    flash will be ttl with ev -0.7 to -1.3
    AF.S

    overall still ok with the output

    1. problem is the shutter speed will auto lower to 1/15 or 1/20 so some movement shots will have double image.
    anyway to set it to up the shutter speed?
    is K-5 have a mode call AT mode? so will have a fix shutter speed and F number only ISO is auto?
    or you will recommand Manual mode so the flash will auto itself with ttl?

    2. is the bound flash issue... i can set the flash to point up... with TTL, looks like will output full power... how to set for the bound flash?

    sorry for the bad english...

  2. #2

    Default

    Tav mode for k5 .
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  3. #3

    Default Re: Flash question

    Quote Originally Posted by JinG14 View Post
    Tav mode for k5 .
    got try? good to work with flash?

  4. #4

    Default Re: Flash question

    I use manual on camera and manual on flash.

    1. Set the camera for ambient w/o turning on the flash 1st.
    The guideline is that you want
    a. Fast enough motion stopping speed. (eg. 1/80; 1/125)
    b. The ambient exposure is enough on the test shot, but it does not need to be proper exposure (usually 1-2 stops under); Trying to meet exact exposure in low light and good shutter speed is rather taxing on the settings.
    c. Enough DOF to be tolerant to focus error or focus shifts (eg. subject shifting)
    d. Acceptable ISO at normal viewing sizes (eg. ISO1600)

    Eg. 1/125; f2.8; ISO1600
    Result : Ambient is -1Ev underexposed

    2. Set flash power to light up the subject to be properly exposed
    (Eg. 1/16 power)
    a. Try not to reach 1/1 as recycle time will be too slow for follow up shots
    b. Typically, since ISO is high, flash power does not need to be so high.


    Sometimes exposure will be off by 0.5 to 1ev, but easily correctable in post.



    I usually don't trust PTTL with bounced flash.
    Auto ISO does not work well with flash imo.

  5. #5
    Moderator catchlights's Avatar
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    Default Re: Flash question

    Quote Originally Posted by Moonlightsg View Post
    Flash question

    last week, I shot for friends wedding with k-x + *16-50 + Sigma 610 std...
    i will set the iso to 100-400 or 100-800 f4-8 with AV mode
    flash will be ttl with ev -0.7 to -1.3
    AF.S

    overall still ok with the output

    1. problem is the shutter speed will auto lower to 1/15 or 1/20 so some movement shots will have double image.
    anyway to set it to up the shutter speed?
    is K-5 have a mode call AT mode? so will have a fix shutter speed and F number only ISO is auto?
    or you will recommand Manual mode so the flash will auto itself with ttl?

    2. is the bound flash issue... i can set the flash to point up... with TTL, looks like will output full power... how to set for the bound flash?

    sorry for the bad english...
    when you use bounce flash, the flash light will travel longer distance, bounce off a surface, it may left only 20% of the light reaches the subject, so when using TTL mode, the camera meter the flash light thru the lens and instruct the flash to output more light for compensating to get the correct exposure, so it may max out the flash power.

    You do want to max out the flash power when using bounce light, you can try..
    use higher ISO,
    use bigger aperture,
    bounce only when the ceiling is low,
    bounce only in a small confine area,
    get a more powerful flash light
    Shoot to Live, Live to Shoot
    www.benjaminloo.com | iStock portfolio

  6. #6

    Default Re: Flash question

    Quote Originally Posted by pinholecam View Post
    I use manual on camera and manual on flash.

    1. Set the camera for ambient w/o turning on the flash 1st.
    The guideline is that you want
    a. Fast enough motion stopping speed. (eg. 1/80; 1/125)
    b. The ambient exposure is enough on the test shot, but it does not need to be proper exposure (usually 1-2 stops under); Trying to meet exact exposure in low light and good shutter speed is rather taxing on the settings.
    c. Enough DOF to be tolerant to focus error or focus shifts (eg. subject shifting)
    d. Acceptable ISO at normal viewing sizes (eg. ISO1600)

    Eg. 1/125; f2.8; ISO1600
    Result : Ambient is -1Ev underexposed

    2. Set flash power to light up the subject to be properly exposed
    (Eg. 1/16 power)
    a. Try not to reach 1/1 as recycle time will be too slow for follow up shots
    b. Typically, since ISO is high, flash power does not need to be so high.


    Sometimes exposure will be off by 0.5 to 1ev, but easily correctable in post.



    I usually don't trust PTTL with bounced flash.
    Auto ISO does not work well with flash imo.
    you are using bound or direct with the above?
    Last edited by Moonlightsg; 21st September 2011 at 04:18 PM.

  7. #7

    Default Re: Flash question

    Quote Originally Posted by catchlights View Post
    when you use bounce flash, the flash light will travel longer distance, bounce off a surface, it may left only 20% of the light reaches the subject, so when using TTL mode, the camera meter the flash light thru the lens and instruct the flash to output more light for compensating to get the correct exposure, so it may max out the flash power.

    You do want to max out the flash power when using bounce light, you can try..
    use higher ISO,
    use bigger aperture,
    bounce only when the ceiling is low,
    bounce only in a small confine area,
    get a more powerful flash light
    will the body smart enough to know there is a bound flash happen? looks like it don't care and just full burst....
    if manual flash, normally will set to 1/8, or 1/16? will it be too weak for 1/16? because flash only have 1/1 or 1/16 setting... i know different room different output... just want to know a est.

  8. #8

    Default Re: Flash question

    P-TTL is not really reliable. The best workaround is to get a flash with A mode (the pentax 540 / Metz 58 etc) then use it with the camera in manual mode.

    If that is not possible then you will need to follow pinholecam's advice and learn how to use both the camera and the flash in M mode.

  9. #9

    Default Re: Flash question

    Quote Originally Posted by CorneliusK View Post
    P-TTL is not really reliable. The best workaround is to get a flash with A mode (the pentax 540 / Metz 58 etc) then use it with the camera in manual mode.

    If that is not possible then you will need to follow pinholecam's advice and learn how to use both the camera and the flash in M mode.
    ok thanks, now understand the Auto mode in Metz 58 is not the same as Pttl...

  10. #10

    Default Re: Flash question

    Quote Originally Posted by Moonlightsg View Post
    Flash question

    last week, I shot for friends wedding with k-x + *16-50 + Sigma 610 std...
    i will set the iso to 100-400 or 100-800 f4-8 with AV mode
    flash will be ttl with ev -0.7 to -1.3
    AF.S

    overall still ok with the output

    1. problem is the shutter speed will auto lower to 1/15 or 1/20 so some movement shots will have double image.
    anyway to set it to up the shutter speed?
    is K-5 have a mode call AT mode? so will have a fix shutter speed and F number only ISO is auto?
    or you will recommand Manual mode so the flash will auto itself with ttl?

    2. is the bound flash issue... i can set the flash to point up... with TTL, looks like will output full power... how to set for the bound flash?

    sorry for the bad english...
    Pinholecam answered your question very well. When shooting flash photography, it is ideal and best to use M mode at the body, then P-TTL or Manual at the flash. Reason being you want total control of the settings at the body so that you can use shutter speed to control ambient exposure while P-TTL will determine its output according to the settings at the body. Visit Neil Van Nerkerk's website about Flash Photography. You have not understand how flash photography actually works so go read up. If still have any questions, feel free to ask. I am sure many pentaxians are glad to help.

    Quote Originally Posted by Moonlightsg View Post
    you are using bound or direct with the above?
    Depends on the environment. If indoor, will be bounce. If outdoor, mixture of bounce and direct. Using direct at indoor typically will produce very harsh light and shadow on the subject so its definitely a no-no.

    Quote Originally Posted by Moonlightsg View Post
    will the body smart enough to know there is a bound flash happen? looks like it don't care and just full burst....
    if manual flash, normally will set to 1/8, or 1/16? will it be too weak for 1/16? because flash only have 1/1 or 1/16 setting... i know different room different output... just want to know a est.
    Don't confuse bounce flash with output. You must understand that the body uses P-TTL to determine how much output to use from the flash. So regardless of bounce or direct, its P-TTL that will determine the output. How P-TTL determine the correct output is by using a pre-flash to meter the scene. This pre-flash is discharged just right before the actual output, so you mostly won't notice it. From this pre-flash, P-TTL will determine to use more or less output. Like what catchlights mentioned, bounce flash will lose power as it travel and bounce, so its just understandable that it will compensate by full burst.

    I hope I didn't confuse you further.
    Aaron Neo | flickr

  11. #11

    Default Re: Flash question

    Actually there is some basis to moonlightsg's impression that the camera tends to fire full power when set to bounce mode, since there are many reports of the pentax flash system's tendency to massively overexpose when set to bounce mode. I myself have experienced this on numerous occasions.

  12. #12

    Default Re: Flash question

    Quote Originally Posted by neon2 View Post
    Pinholecam answered your question very well. When shooting flash photography, it is ideal and best to use M mode at the body, then P-TTL or Manual at the flash. Reason being you want total control of the settings at the body so that you can use shutter speed to control ambient exposure while P-TTL will determine its output according to the settings at the body. Visit Neil Van Nerkerk's website about Flash Photography. You have not understand how flash photography actually works so go read up. If still have any questions, feel free to ask. I am sure many pentaxians are glad to help.



    Depends on the environment. If indoor, will be bounce. If outdoor, mixture of bounce and direct. Using direct at indoor typically will produce very harsh light and shadow on the subject so its definitely a no-no.



    Don't confuse bounce flash with output. You must understand that the body uses P-TTL to determine how much output to use from the flash. So regardless of bounce or direct, its P-TTL that will determine the output. How P-TTL determine the correct output is by using a pre-flash to meter the scene. This pre-flash is discharged just right before the actual output, so you mostly won't notice it. From this pre-flash, P-TTL will determine to use more or less output. Like what catchlights mentioned, bounce flash will lose power as it travel and bounce, so its just understandable that it will compensate by full burst.

    I hope I didn't confuse you further.
    I think i understand how flash and camera work...
    but don't understand how the p-ttl will react or how smart is can be...
    understand the camera use slow shutter speed is to get more Ambient lighting...

    and yes direct flash will be harsh with shadow...

    yes, bounce flash is hard for the flash or cam to determine the output... hoping someone to surprise me that there is some way the smarter cam/flash can do it... looks like try and error is the way... also my flash only have 1/16 or 1/1 mode... so i don't have much option to play with...
    so there is a pre-flash going on.... really didn't notice it.... i always thought is the red light beam from the flash determine the flash power....so is only for foucing only...

    thank you!

  13. #13

    Default Re: Flash question

    Quote Originally Posted by CorneliusK View Post
    Actually there is some basis to moonlightsg's impression that the camera tends to fire full power when set to bounce mode, since there are many reports of the pentax flash system's tendency to massively overexpose when set to bounce mode. I myself have experienced this on numerous occasions.
    yes... i have plan at the very begining that i know the bounce mode is not easly... so almost whole wedding i use direct with PTTL is more safe...
    i only try a few shot with bounce, fail, and i got no time for it already....

    actually, there was a paid photographer + another friend(who did wedding day shooting before) shot for this wedding....

  14. #14

    Default Re: Flash question

    Quote Originally Posted by CorneliusK View Post
    Actually there is some basis to moonlightsg's impression that the camera tends to fire full power when set to bounce mode, since there are many reports of the pentax flash system's tendency to massively overexpose when set to bounce mode. I myself have experienced this on numerous occasions.
    I've encountered this rather frequently on a Metz48.
    But seems improved with K5 firmware upgrade to 1.03.
    Have not bothered to use PTTL too often to further verify it though.

    My brother uses AF540 and he does not see to have any issues.

  15. #15

    Default Re: Flash question

    Quote Originally Posted by Moonlightsg View Post
    I think i understand how flash and camera work...
    but don't understand how the p-ttl will react or how smart is can be...
    understand the camera use slow shutter speed is to get more Ambient lighting...

    and yes direct flash will be harsh with shadow...

    yes, bounce flash is hard for the flash or cam to determine the output... hoping someone to surprise me that there is some way the smarter cam/flash can do it... looks like try and error is the way... also my flash only have 1/16 or 1/1 mode... so i don't have much option to play with...
    so there is a pre-flash going on.... really didn't notice it.... i always thought is the red light beam from the flash determine the flash power....so is only for foucing only...

    thank you!
    My personal suspicion is that pre-flash is just a fast and weak strobe of light (since the power is reserved for the main flash). So if its a largish area or the camera cannot really capture the pre-flash to gauge the flash setting to use, it anyhow 'hamtam'
    (assuming that its a large space that needs a lot of flash power)

    What flash are you using and is the firmware on your camera the latest one?

  16. #16

    Default Re: Flash question

    Quote Originally Posted by pinholecam View Post
    My personal suspicion is that pre-flash is just a fast and weak strobe of light (since the power is reserved for the main flash). So if its a largish area or the camera cannot really capture the pre-flash to gauge the flash setting to use, it anyhow 'hamtam'
    (assuming that its a large space that needs a lot of flash power)

    What flash are you using and is the firmware on your camera the latest one?
    K-x with ver 1.1
    Sigma EF-610 DG ST
    if there is a pre-flash, yes, i think the metering time not get back much return light that why go for full power...
    will try the manual way this afternoon during the site visit of the company event (flash 1/16, cam with M mode, ISO 1600, F4 and slowly play with the shutter speed....)

  17. #17

    Default Re: Flash question

    I don't buy this. If the final image can be so badly overexposed by the bounced flash, then there should be enough of the metering pre flashed reflected for a proper reading. If the area is simply too big for the flash to fill, the final image will simply look underexposed.

    This is a bug, plain and simple. It is not my intention to start a brand war here but the difference between pentax and nikon in this respect is goddamn night and day.

  18. #18

    Default Re: Flash question

    Quote Originally Posted by CorneliusK View Post
    I don't buy this. If the final image can be so badly overexposed by the bounced flash, then there should be enough of the metering pre flashed reflected for a proper reading. If the area is simply too big for the flash to fill, the final image will simply look underexposed.

    This is a bug, plain and simple. It is not my intention to start a brand war here but the difference between pentax and nikon in this respect is goddamn night and day.

    Like I said, just my thoughts on it.
    Its how the camera 'sees' the pre-flash not how much pre-flash there actually is.
    Its also how the system (ie. Pentax + flash) is programmed to handle the situation. (ie. just wack full power when in doubt = bad)


    No one is saying Pentax pttl in bounce is good.

  19. #19

    Default Re: Flash question

    Quote Originally Posted by Moonlightsg View Post
    K-x with ver 1.1
    Sigma EF-610 DG ST
    if there is a pre-flash, yes, i think the metering time not get back much return light that why go for full power...
    will try the manual way this afternoon during the site visit of the company event (flash 1/16, cam with M mode, ISO 1600, F4 and slowly play with the shutter speed....)
    Just got to try and try with some bit of read up on flash photography.
    Even the pros 'cheat' with setup test shots and light meter readings, so its just the same with testing a shot or two and fudging

  20. #20

    Default Re: Flash question

    Quote Originally Posted by CorneliusK View Post
    I don't buy this. If the final image can be so badly overexposed by the bounced flash, then there should be enough of the metering pre flashed reflected for a proper reading. If the area is simply too big for the flash to fill, the final image will simply look underexposed.

    This is a bug, plain and simple. It is not my intention to start a brand war here but the difference between pentax and nikon in this respect is goddamn night and day.
    i would say they have not plan until this function in Pttl...?
    the place i try at the house may be a bit hight... about 4 meter ceiling....
    also try at the wedding dinner place with low ceiling, just 1/2 meter more than our HDB.... i can almost touch the ceiling with just a chair...
    i saw my nikon user friend just bounce flash all the way and no pp needed and play at the wedding dinner.... i PP until like mad about 30-50% shot need to pp.... may be i more demanding....
    the Paid photograder even better... 50D +11-16mm and 550D with a manual lens... whole morning no flash needed even indoor! i wounder the outcome....

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