Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
08-18-2013, 04:33 PM   #1
Senior Member




Join Date: Jun 2013
Posts: 118
Exposure using flash on K200D with M lens

Hoping someone can help with my exposure metering problems on my K200D with M lens, using the built-in flash. When I am in low light indoors, when I use the flash with a large aperture, I often get completely blown out photos.

Without flash, I am following Adam's procedure here: https://www.pentaxforums.com/forums/pentax-lens-articles/110657-how-use-meter...k-x-k-7-a.html
So I set the camera on M, set the aperture manually using the aperture ring on the lens, press the green button to meter, and then take the picture. This seems to work fine.

With flash, using the same procedure, I get completely blown out photos at large apertures. It is as if the camera does not set the shutter speed properly with the flash. There must be some setting I am missing.. Looking at the manual, there is a sentence that reads "the built-in flash fully discharges for lenses without a function to set aperture lens ring to A". This sounds like it addresses my situation, but it also implies that the flash can "partially" discharge? So related question is - does the flash vary in intensity depending on exposure needs? And then does this mean that you basically cannot use the flash with M lenses? Or that there is a set aperture or shutter speed that syncs with the flash?


Last edited by Takumar55; 08-18-2013 at 04:46 PM. Reason: typos
08-18-2013, 04:52 PM   #2
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 40,974
When using a flash, the aperture is what primarily controls the exposure. Most older flashes have a table on the back that tells you what aperture to use at what distance/intensity combination. If your flash doesn't have such a table, then a bit of trial-and-error will be required, so go ahead and lock set your shutter speed to the flash sync speed and test a variety of aperture settings.

There is no automation whatsoever when using flashes with M and K lenses on modern Pentax DSLRs, as they use P-TTL (calculated) and not TTL (real-time) flash metering. The only DSLRs that do support TTL flashes are the *ist D, DS, and DS2.

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)



PentaxForums.com's high server and development costs are user-supported. You can help cover those costs by donating. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

08-18-2013, 05:04 PM   #3
Pentaxian
maxfield_photo's Avatar

Join Date: Mar 2011
Location: Cincinnati, OH
Posts: 1,216
Do you have your camera set to "allow" the use of the aperture ring? If the flash can't read the aperture I believe it will always fire at full power in pTTL mode.

There is a pretty simple hack for the K-mount that involves unscrewing the ring and shorting the "A" pin with some tin foil. Once you've done that, the camera will think every lens you mount has an "A" position on the aperture ring, and all you have to do is dial in the aperture on the camera to match your lens.

Oh, and don't use Auto ISO
08-18-2013, 05:42 PM   #4
Senior Member




Join Date: Jun 2013
Posts: 118
Original Poster
QuoteOriginally posted by Adam Quote
When using a flash, the aperture is what primarily controls the exposure. Most older flashes have a table on the back that tells you what aperture to use at what distance/intensity combination. If your flash doesn't have such a table, then a bit of trial-and-error will be required, so go ahead and lock set your shutter speed to the flash sync speed and test a variety of aperture settings.

There is no automation whatsoever when using flashes with M and K lenses on modern Pentax DSLRs, as they use P-TTL (calculated) and not TTL (real-time) flash metering. The only DSLRs that do support TTL flashes are the *ist D, DS, and DS2.
Forget to mention I'm using the built-in flash.

But it sounds like I need to figure out which aperture and shutter combinations work with the built-in flash, and then set them accordingly?

08-18-2013, 05:46 PM   #5
Senior Member




Join Date: Jun 2013
Posts: 118
Original Poster
QuoteOriginally posted by maxfield_photo Quote
Do you have your camera set to "allow" the use of the aperture ring? If the flash can't read the aperture I believe it will always fire at full power in pTTL mode.

There is a pretty simple hack for the K-mount that involves unscrewing the ring and shorting the "A" pin with some tin foil. Once you've done that, the camera will think every lens you mount has an "A" position on the aperture ring, and all you have to do is dial in the aperture on the camera to match your lens.

Oh, and don't use Auto ISO

It's an M lens, so I don't think I can use the "allow" feature. But what you say here matches with what the manual says - the wording there is just a little ambiguous.

Thanks for the shorting tip. I've seen it mentioned, but never thought about what it meant.

No Auto ISO - using Manual mode on the camera.
08-18-2013, 05:49 PM   #6
Pentaxian




Join Date: Mar 2010
Location: Frankfurt am Main
Posts: 1,045
The built-in flash of the K200D is specified with GN (maximum Guide Number) of 13 for ISO 100 and metric system.
As the built-in flash cannot change the area its light covers, GN13 is independend from lens focus length.
If the flash always uses its full capacity, you get the correct aperture by deviding the GN by the object distance in meters (for ISO 100).

So, for a distance of 4 meters the aperture at ISO 100 would be 13/4 --> F3.25. Set aperture to one of the nearest half aperture stops, F2.8 or F3.5 (depending on subject).
If you are too far away to get a valid aperture (aperture value gets too small for this lens), adjust ISO instead.

Last edited by RKKS08; 08-18-2013 at 05:58 PM. Reason: cosmetic
08-18-2013, 05:50 PM   #7
Veteran Member




Join Date: Mar 2007
Location: Christchurch, New Zealand
Photos: Gallery
Posts: 433
QuoteOriginally posted by Takumar55 Quote
Hoping someone can help with my exposure metering problems on my K200D with M lens, using the built-in flash. When I am in low light indoors, when I use the flash with a large aperture, I often get completely blown out photos.

Without flash, I am following Adam's procedure here: https://www.pentaxforums.com/forums/pentax-lens-articles/110657-how-use-meter...k-x-k-7-a.html
So I set the camera on M, set the aperture manually using the aperture ring on the lens, press the green button to meter, and then take the picture. This seems to work fine.

With flash, using the same procedure, I get completely blown out photos at large apertures. It is as if the camera does not set the shutter speed properly with the flash. There must be some setting I am missing.. Looking at the manual, there is a sentence that reads "the built-in flash fully discharges for lenses without a function to set aperture lens ring to A". This sounds like it addresses my situation, but it also implies that the flash can "partially" discharge? So related question is - does the flash vary in intensity depending on exposure needs? And then does this mean that you basically cannot use the flash with M lenses? Or that there is a set aperture or shutter speed that syncs with the flash?
You're correct. If you use a K or M lens (any lens that does not have an A setting), the built-in flash which is P-TTL on a K200D will fire at FULL power.

Your options are, unless you want to modify a lens, to use A series or newer lenses (A, F, FA, FA J, or any DA seriees lens) preferably with the aperture on the lens set to A, or use an external flash that allows you to control the flash power (either a flash with its own light sensor (Auto flash) or a flash with manual controls (Manual flash)).

Regards

Chris
08-18-2013, 05:52 PM   #8
Veteran Member




Join Date: Mar 2007
Location: Christchurch, New Zealand
Photos: Gallery
Posts: 433
QuoteOriginally posted by Takumar55 Quote
Hoping someone can help with my exposure metering problems on my K200D with M lens, using the built-in flash. When I am in low light indoors, when I use the flash with a large aperture, I often get completely blown out photos.

Without flash, I am following Adam's procedure here: https://www.pentaxforums.com/forums/pentax-lens-articles/110657-how-use-meter...k-x-k-7-a.html
So I set the camera on M, set the aperture manually using the aperture ring on the lens, press the green button to meter, and then take the picture. This seems to work fine.

With flash, using the same procedure, I get completely blown out photos at large apertures. It is as if the camera does not set the shutter speed properly with the flash. There must be some setting I am missing.. Looking at the manual, there is a sentence that reads "the built-in flash fully discharges for lenses without a function to set aperture lens ring to A". This sounds like it addresses my situation, but it also implies that the flash can "partially" discharge? So related question is - does the flash vary in intensity depending on exposure needs? And then does this mean that you basically cannot use the flash with M lenses? Or that there is a set aperture or shutter speed that syncs with the flash?
You're correct. If you use a K or M lens (any lens that does not have an A setting), the built-in flash which is P-TTL on a K200D will fire at FULL power.

Your options are, unless you want to modify a lens, to use A series or newer lenses (A, F, FA, FA J, or any DA seriees lens) preferably with the aperture on the lens set to A, or use an external flash that allows you to control the flash power (either a flash with its own light sensor (Auto flash) or a flash with manual controls (Manual flash)).

Regards

Chris

08-18-2013, 05:57 PM   #9
Senior Member




Join Date: Jun 2013
Posts: 118
Original Poster
Thanks for the responses! I just tried the same shots using my A lens, and it works fine. So everything's exactly as you've all described here. I'll have to be cognizant of what I can and can't do with the M lens. Good to know it's just my lack of knowledge here and nothing worse.
08-18-2013, 06:01 PM   #10
Senior Member




Join Date: Jun 2013
Posts: 118
Original Poster
QuoteOriginally posted by RKKS08 Quote
The built-in flash of the K200D is specified with GN (maximum Guide Number) of 13 for ISO 100 and metric system.
As the built-in flash cannot change the area its light covers, GN13 is independend from lens focus length.
If the flash always uses its full capacity, you get the correct aperture by deviding the GN by the object distance in meters (for ISO 100).

So, for a distance of 4 meters the aperture at ISO 100 would be 13/4 --> F3.25. Set aperture to one of the nearest half aperture stops, F2.8 or F3.5 (depending on subject).
If you are too far away to get a valid aperture (aperture value gets too small for this lens), adjust ISO instead.

...and this rough calculation worked on the M lens!
08-18-2013, 06:18 PM   #11
Pentaxian




Join Date: Mar 2010
Location: Frankfurt am Main
Posts: 1,045
QuoteQuote:
...and this rough calculation worked on the M lens!
This was the ONLY way you could use flash before the age of (affordable) thyristor flashes began, I think about 1970.

And it is still the recommended technique if you use flash at night outside for photographing people.
This is one of the situations where TTL and xyz-TTL have their limits - totally black background and blown out faces. Contrast measurement of pTTL improves it a bit, but most times old school manual calculation gives much better results.
08-18-2013, 06:36 PM   #12
Senior Member




Join Date: Jun 2013
Posts: 118
Original Poster
Is there a recommended shutter speed? I remember 60 or 90 being the "flash" speed. In my previous picture, I had the shutter at 90.

Edit: Ah, I see. 180 is max with built-in flash

Last edited by Takumar55; 08-18-2013 at 06:42 PM.
08-18-2013, 06:45 PM   #13
Pentaxian
Not a Number's Avatar

Join Date: Mar 2012
Location: Venice, CA
Posts: 3,898
You could always create a spreadsheet and make a cheat sheet using the formula f-stop = Guide Number / Distance. You can guesstimate the distance off the scale on the lens focusing ring. It would be like to good old days of using flash bulbs.
08-18-2013, 06:51 PM   #14
Pentaxian




Join Date: Mar 2010
Location: Frankfurt am Main
Posts: 1,045
QuoteOriginally posted by Takumar55 Quote
Is there a recommended shutter speed? I remember 60 or 90 being the "flash" speed. In my previous picture, I had the shutter at 90. Edit: Ah, I see. 180 is max with built-in flash
If you want to include existing ambient/natural light to mix with the flash light, you may want to use a longer exposure time. You probably must close the aperture a bit more than the calculation recommends, but how much is more a result of experience than precise measurement/calculation.
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!
aperture, camera, exposure, flash, k200d, lens, lenses, pentax help, photography, photos, shutter
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Using flash with manual lens dmeadows85 Flashes, Lighting, and Studio 7 01-28-2012 08:03 PM
using manual lens on K2000 pano1 Troubleshooting and Beginner Help 8 03-29-2011 04:32 AM
Is there a 1/5 sec limitation with manual lens on K200D? cbaytan Pentax DSLR Discussion 13 12-28-2009 09:32 PM
Using built-in flash on K100d with a manual lens seeker Pentax DSLR Discussion 2 04-18-2007 10:55 AM
Flash using Manual 50mm 1.4 lens Wildfire_ja Flashes, Lighting, and Studio 5 12-13-2006 08:10 AM



All times are GMT -7. The time now is 05:36 PM. | See also: NikonForums.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