Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
01-01-2014, 07:46 AM - 3 Likes   #1
Pentaxian
Gray's Avatar

Join Date: Oct 2011
Location: Cape Town
Photos: Gallery
Posts: 387
Gray's Rule: K-5 & bounced flash overexposure workaround

A little new year's present for everyone.

I'm an outdoor photographer, but have recently become interested in indoor flash photography. Besides the on-board flash of the K-5/K-5II, I have a AF-360FGZ and AF-540FGZ. I been playing and experimenting with all three flashes, mounted and wireless external flashes, with some forbearance from my friends and family.

Like many I have have bumped heads with the K-7/K-5/K-5II bounced flash P-TTL overexposure problem, and been extremely irritated by it and Pentax/Ricoh's public inability even to acknowledge the problem or suggest workarounds. Pentax insiders have hinted at a hardware problem with the K-7 & K-5 series being the cause - something which apparently is not fixable by a firmware update.

Anyway, I've done a fair amount of testing with different lenses using the 360 and 540 flashes and have come up with this rule of thumb:

In words
  • If you're using the wide angle diffuser panel, set total flash exposure compensation to -3.0
  • If the current focal length (zoom or prime) is less than about 28mm, or if your prime lens is fast (max. aperture = greater than f/2.4): dial the total flash exposure compensation (either on the camera and/or flash) to -2.0
  • Otherwise leave the flash exposure compensation on the camera (& flash) set to 0.0

or in shorthand:

Gray's Rule
  • a) if using wide angle diffuser : -3.0
  • b) else if f <= 28mm or fast prime* : -2.0
  • c) else : 0.0

*fast prime = max aperture larger than f/2.4 whatever the focal length

Caveats:
  • the rule is not perfect, but I have found it holds true for me in most situations with apertures f/8 and greater
  • your experience may be different; you may wish to shift the flash exposure compensation corrections up by half a stop or a full stop to -2.5, -1.5 or -2.0, -1.0.
  • a), b) & c) options are mutually exclusive and apply downwards, i.e. if a) is false, then test b), if b) is false, then c) applies.
  • remember flash compensation on the camera and on the flash itself is cumulative, e.g. (camera -2.0) + (flash -1.0) = (total -3.0)
  • the rule applies for LV use too
  • tested with matrix (segmented) metering
  • tested on AF zoom and AF prime lenses from 8mm to 250mm in indoor conditions with a white ceiling, within the relevant flash's range (from close up to about 5 or 6 m / 15 or 18ft)
  • not tested with manual focus "A" lenses
  • tested with P-AV and AV using
    - K-5 and K-5II
    - zooms: DA 18-135 WR, DA* 60-250, Sigma 8-16, 17-70 "C", Tamron 28-75
    - primes: DA 15, 70, FA 20, 31, 43, 50/1.7, 77, 100/2.8, 135

I'd be very interested to know if this rule can be applied to the K-7 and bounced flash, and how useful or not other K-5 users find it. It's a work in progress and will certainly benefit from pooled experience.

Happy New Year!


Last edited by Gray; 01-16-2014 at 09:36 PM. Reason: edited to add metering mode
01-01-2014, 09:12 AM   #2
Veteran Member
gbeaton's Avatar

Join Date: Apr 2012
Location: Montreal
Photos: Gallery | Albums
Posts: 338
Thanks for the info. You certainly have a lot of patience!
01-02-2014, 12:50 AM   #3
Veteran Member
adwb's Avatar

Join Date: Sep 2009
Location: Bristol UK
Photos: Gallery
Posts: 1,631
All my bodies are permanently set to -2 fec and have been since K10 days.
01-08-2014, 04:09 PM   #4
Site Supporter




Join Date: Apr 2008
Location: Central Ohio (formerly SF Bay Area)
Posts: 1,490
QuoteOriginally posted by Gray Quote
Gray's Rule
  • a) if using wide angle diffuser : -3.0
  • b) else if f <= 28mm or fast prime* : -2.0
  • c) else : 0.0

*fast prime = max aperture larger than f/2.4 whatever the focal length
Fantastic, thanks for this! I wish there were an actual solution rather than just workarounds, but this seems pretty straightforward.

Have you noticed any distance dependence (either camera-to-subject or flash-to-bounce-surface)?

01-08-2014, 07:43 PM   #5
Pentaxian
Gray's Avatar

Join Date: Oct 2011
Location: Cape Town
Photos: Gallery
Posts: 387
Original Poster
QuoteOriginally posted by Quicksand Quote
Have you noticed any distance dependence (either camera-to-subject or flash-to-bounce-surface)?
I've tested it in domestic situations: in rooms with white ceilings at normal height (not double-vaulted) and/or light-coloured walls. Having more white in the subject does make a difference, but not too much. My hope is that others would try the rule and let us know their results so that it can be refined or completely reworked.
01-09-2014, 05:56 AM   #6
Veteran Member




Join Date: Sep 2013
Posts: 306
I did give up with k5&pttl external flash hopeless combination. A-mode in flash is working much better with k5. If want use pttl better get more new body. Even K30 pttl is much better.
01-13-2014, 07:54 AM   #7
Site Supporter
GeneV's Avatar

Join Date: Oct 2008
Location: Albuquerque NM
Photos: Albums
Posts: 9,772
I have been a big believer in bounce for years, but the last body which really did well with P-TTL and bounce was the K20d. That is sad, and I had hoped with the K-5II, the problems of the K-5 had been improved upon, but not in this area. For some reason, the K-5 bodies also will not provide good bounce results in rooms with higher ceilings where the K20d would. It is lucky that the sensor in the K-5 series produces a raw file that will handle a good deal of adjustment for the setting imposing underexposure that is required.
01-16-2014, 05:07 AM   #8
Pentaxian




Join Date: Apr 2010
Location: Wangaratta, Victoria
Photos: Gallery
Posts: 3,359
I haven't put a lot of work into it, but with my Sigma EF-530, I just get confused with bounce flash.
(I'll have to do the work, won't I?)
The unit has three settings - TTL , High power and Low power.
Regardless of what I think is appropriate, I review the image and then adjust the power setting.
Nothing seems consistent and it is most frustrating.
If I hadn't put my DS out on permanent loan to a friend, I would use it exclusively for flash, to alleviate the frustration.

01-16-2014, 09:59 AM   #9
Loyal Site Supporter




Join Date: Aug 2011
Photos: Albums
Posts: 1,850
Gray, what is the metering setting on your camera when you did the test?
I am curious because in the past weekend, in my daughter's dress-up birthday party at home, I used bouncing flash from 540 on K5II. Light is very uneven in the living room so most of photos were taken with flash. Flash was set P-TTL without adjusting, camera was set center spot meter. I didn't adjust the output on both camera and flash in most time. Exposure were accurate in 95% shots.
I guess if camera meters the background light, it might overexpose the closer subject.

instead, I noticed I had to set flash output to -1.7 if I point the flash directly to the subject in the fill-in flash to avoid over exposure.
01-16-2014, 09:34 PM   #10
Pentaxian
Gray's Avatar

Join Date: Oct 2011
Location: Cape Town
Photos: Gallery
Posts: 387
Original Poster
QuoteOriginally posted by grahame Quote
Gray, what is the metering setting on your camera when you did the test?
Matrix metering. I haven't tested spot or centre-weighted metering.
01-17-2014, 04:43 AM   #11
Loyal Site Supporter
clackers's Avatar

Join Date: Jul 2013
Location: Melbourne
Photos: Albums
Posts: 8,638
QuoteOriginally posted by Gray Quote
Matrix metering. I haven't tested spot or centre-weighted metering.
Doesn't the camera always use matrix metering for flash purposes?
01-17-2014, 07:20 AM   #12
Site Supporter




Join Date: Jan 2010
Location: Michigan
Photos: Gallery
Posts: 2,153
Looks like the K-01 does not need the Gray's Rule
At 24mm with the pentax AF360fgz pointing at the white ceiling
#1 Gray's Case 1
#2 Case 1 with no compensation

#3 Gray's Case 2
#4 Case 2 with no compensation
Attached Images
View Picture EXIF
PENTAX K-01  Photo 
View Picture EXIF
PENTAX K-01  Photo 
View Picture EXIF
PENTAX K-01  Photo 
View Picture EXIF
PENTAX K-01  Photo 
01-17-2014, 08:18 AM   #13
Pentaxian
Gray's Avatar

Join Date: Oct 2011
Location: Cape Town
Photos: Gallery
Posts: 387
Original Poster
QuoteOriginally posted by clackers Quote
Doesn't the camera always use matrix metering for flash purposes?
I can't find anything in the K-5II manual to confirm that.
05-23-2015, 10:57 PM   #14
New Member




Join Date: Jun 2010
Location: Hong Kong
Posts: 2
QuoteOriginally posted by Gray Quote
A little new year's present for everyone.

I'm an outdoor photographer, but have recently become interested in indoor flash photography. Besides the on-board flash of the K-5/K-5II, I have a AF-360FGZ and AF-540FGZ. I been playing and experimenting with all three flashes, mounted and wireless external flashes, with some forbearance from my friends and family.

Like many I have have bumped heads with the K-7/K-5/K-5II bounced flash P-TTL overexposure problem, and been extremely irritated by it and Pentax/Ricoh's public inability even to acknowledge the problem or suggest workarounds. Pentax insiders have hinted at a hardware problem with the K-7 & K-5 series being the cause - something which apparently is not fixable by a firmware update.

Anyway, I've done a fair amount of testing with different lenses using the 360 and 540 flashes and have come up with this rule of thumb:

In words
  • If you're using the wide angle diffuser panel, set total flash exposure compensation to -3.0
  • If the current focal length (zoom or prime) is less than about 28mm, or if your prime lens is fast (max. aperture = greater than f/2.4): dial the total flash exposure compensation (either on the camera and/or flash) to -2.0
  • Otherwise leave the flash exposure compensation on the camera (& flash) set to 0.0

or in shorthand:

Gray's Rule
  • a) if using wide angle diffuser : -3.0
  • b) else if f <= 28mm or fast prime* : -2.0
  • c) else : 0.0

*fast prime = max aperture larger than f/2.4 whatever the focal length

Caveats:
  • the rule is not perfect, but I have found it holds true for me in most situations with apertures f/8 and greater
  • your experience may be different; you may wish to shift the flash exposure compensation corrections up by half a stop or a full stop to -2.5, -1.5 or -2.0, -1.0.
  • a), b) & c) options are mutually exclusive and apply downwards, i.e. if a) is false, then test b), if b) is false, then c) applies.
  • remember flash compensation on the camera and on the flash itself is cumulative, e.g. (camera -2.0) + (flash -1.0) = (total -3.0)
  • the rule applies for LV use too
  • tested with matrix (segmented) metering
  • tested on AF zoom and AF prime lenses from 8mm to 250mm in indoor conditions with a white ceiling, within the relevant flash's range (from close up to about 5 or 6 m / 15 or 18ft)
  • not tested with manual focus "A" lenses
  • tested with P-AV and AV using
    - K-5 and K-5II
    - zooms: DA 18-135 WR, DA* 60-250, Sigma 8-16, 17-70 "C", Tamron 28-75
    - primes: DA 15, 70, FA 20, 31, 43, 50/1.7, 77, 100/2.8, 135

I'd be very interested to know if this rule can be applied to the K-7 and bounced flash, and how useful or not other K-5 users find it. It's a work in progress and will certainly benefit from pooled experience.

Happy New Year!
This is a nice post and thanks for the hard work.
I revisited the problem about K5 bounced flash (which was talked about in many forums) after I took some flash photos in an evening event. The results were inconsistent and that bugs me. I then tried some test shots at home comparing bounced and direct flash. To my surprise, the results of bounced flash are actually better than direct flash. In one particular situation, direct flash on a subject using wide angle (14-45mm F4.0) actually yielded pictures with massive over exposure. Then I came across your post and I am so glad that I did. I will give your suggestion a bit more trial and so far, it is working well and I have more consistent results. I wonder if anyone else has the similar findings and experience.
05-24-2015, 01:35 AM   #15
Veteran Member
adwb's Avatar

Join Date: Sep 2009
Location: Bristol UK
Photos: Gallery
Posts: 1,631
I have always had all the k 5 bodies of which at one point I had three and the k5ii that I have set perminatly to -2 fec on the bdy which in all cases makes for a softer more fill flash look.

What has become apparent is that reflective surfaces completely fool the meters reading of the preflash and always no matter what the flash angle of the head need to be borne in mind as the more reflective the surface the more the image will be likely be wrongly exposed.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
angle, bounce, bounced, camera, compensation, diffuser, dslr, exposure, flash, k-5, k-5 ii, k-5 iis, k-5ii, k-7, k5, pentax k-5
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Bounced Fill-In Flash w/ Direct Sun. tabl10s Photographic Technique 3 09-05-2013 12:09 AM
Bounced Flash: P-TTL, Auto or Manual? ElvisQ Pentax Q 11 05-23-2013 04:49 AM
Gray's K-5 Images Gray Pentax K-5 7 11-14-2011 08:49 AM
People Daddy's hat, a crystal ball, and bounced flash... heliphoto Post Your Photos! 11 01-31-2010 11:03 PM



All times are GMT -7. The time now is 05:03 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top