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06-24-2010, 09:59 AM   #16
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QuoteOriginally posted by corkboard Quote
Thanks again for the helpful list Canada_Rockies!

Here were my steps

  1. Mount the flash on the camera
    • Flash pointed straight forward
  2. Turn it on
  3. Turn on the camera
  4. Set the camera to Av
    • Camera indicated F/4 and 0.3" for overall exposure of +0
    • Camera ISO set to 100
  5. Select the aperture to match red/green
    • At ISO 100, F/4
  6. Set the flash to red/green auto to match
    • Flash mode slider set to Auto Red
  7. Wait until the flash ready light comes on
  8. [Fn] and enable the flash
    • Flash mode set to Manual Fire
  9. Take a picture
    • Scene is approximately 3-5 meters away

My overall shot is overblown - white refrigerator is over blown, brown cupboards overblown

If I set the overall exposure down to -1, it looks a little better (shutter speed sped up to 1/4)

At this point it seems like a matter of making adjustments - but should the guide settings on the back be a little more reliable?
One more thing to check: is the flash guide set to ISO 100 on the flash? If you have the guide number on the flash wrong the slider will indicate an incorrect aperture. The flash has no way of knowing what you set the camera to in Auto mode.

Try taking a picture at the indicated exposure without the flash. This will tell you if the ambient exposure is too much. 0.3" @ f/4 sounds low to me. Did you turn the lights off for testing?

You could also test by setting your camera to M (manual) exposure, setting the aperture to the aperture indicated on the flash and setting the shutter speed to 1/180. This should eliminate most of the ambient light, unless your kitchen is much brighter than mine.

06-24-2010, 10:16 AM   #17
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Hi Canada_Rockies

The flash guide (ASA slider) was set at 100 - I forgot to mention this

The ambient light at midnight is supplied by a 60W bulb, so it is indeed low light but not pitch black

I'll take another picture without the flash but what I can say - I have tried experimenting with the flash off to double check my exposure isn't whacky, and I'm 99% certain F/4 @ 0.3" gives a correct exposure of +0 on the exposure slider

Regarding setting the shutter speed to 1/180 - this has worked for me as you indicated, it has removed the ambient light.

Is this the subtlety I should be aware of? If I want the source of light to come from my flash, I should set the shutter speed to 1/180, and use the guide + auto mode on the flash?

And if I want to fill flash when there is enough light, I would then leave the Av mode to calculate ambient exposure for me?

Thanks for your guidance and patience!
06-24-2010, 10:27 AM   #18
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QuoteOriginally posted by corkboard Quote
Hi Canada_Rockies

The flash guide (ASA slider) was set at 100 - I forgot to mention this

The ambient light at midnight is supplied by a 60W bulb, so it is indeed low light but not pitch black

I'll take another picture without the flash but what I can say - I have tried experimenting with the flash off to double check my exposure isn't whacky, and I'm 99% certain F/4 @ 0.3" gives a correct exposure of +0 on the exposure slider

Regarding setting the shutter speed to 1/180 - this has worked for me as you indicated, it has removed the ambient light.

Is this the subtlety I should be aware of? If I want the source of light to come from my flash, I should set the shutter speed to 1/180, and use the guide + auto mode on the flash?

And if I want to fill flash when there is enough light, I would then leave the Av mode to calculate ambient exposure for me?

Thanks for your guidance and patience!
We are getting into the fine print here. To use the flash as fill, not total exposure, set the f/stop on the camera to one or two stops more than the flash indicates. If the flash says f/4, try setting Av to f/5.6 or f/8. That will reduce the exposure from the flash, while leaving the ambient exposure normal.

It sounds as if you are having fun!
06-24-2010, 10:58 AM   #19
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Hehe I'm trying not to get too frustrated - the first few days was like this:

I guess I'm trying to figure out a reliable systematic way to take fewer test pictures and understand the results that I'm going to get before I hit the shutter release button. I think at this point I've got to keep testing and build experience

You guys have given me some good rules of thumb to start with at least =)

06-24-2010, 11:32 AM   #20
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corkboard

it sounds like you are getting close, but a couple of points after reading all of the posts, some for your understanding and benefit overall, some for the specific issue of using the flash.

First of all, there are 4 basic flash modes available (depending on flash and camera). These are manual, Auto, TTL and P-TTL.
Manual is just what it sounds like, You have options of flash power 1 1/2, 1/4 1/8 etc, each of these represents a 1 F Stop difference, relitive to the full power (setting 1). Full Power gives the flash illumination that is stated in the spec sheet for the guide number, either in feet or meters, at ISO 100 and F1.0. You have to do all the calculations manually to determine exposure, based on subject distance, ISO setting, and lens Aperture.

Auto, is the earliest auto exposure mode for flashes. This mode requires that the flash has it's own photocell to meter the light reflected back from the subject. In this mode, you set the flash to auto, set the ISO on the flash to the same ISO as the camera, and the Aperture on the flash to the aperture on the camera. the flash then has a range of distance scales that tell the user for the settings whether the flash can work with the user's subject to camera distance.

TTL is the first version where flash is metered through the lens, and the camera takes light reflected off the surface of the film, or off the sensor in a dslr, and turns the flash off when the exposure is sufficient. TTL is only supported on th epentax *istD and DS digital cameras.

P-TTL is the latest version of flash control, and no th eP does not really stand for pentax. P-TTL flash metering uses a preflash, which is measured by the camera's normal metering sensor, and the flash exposure is calculated, to include ambient light and the camera settings to control the duration and power of the flash. It is important to note here that the flash output is calculated, as opposed to measured, and that is the biggest difference between P-TTL and TTL, one measures the light hitting the sensor (or film) and turns the flash off when teh correct amount of light has been reflected back, the other measures ambient light, and the light reflected from the preflash, and then calculates the duration of the flash based on the mesurement of the preflash. During the exposure itself, nothing is actually measured. SOme claim P-TTL was introduced to get around issues with different reflective coefficients from different film and digital sensors, but more porbably it is cheaper as it reduces the number of metering sensors. Additionally the preflash pulses can be used to control/communicate with remote wireless flashes.

The benefit of P-TTL over TTL is in blended flash modes. With TTL if you have high ambient light, although the flash shuts off, the camera settings may keep the shutter open, adding additional exposure, therefore leading to over esposure. TTL works best when the camera flash is supplying the majority of light, or when you program the exposure (without flash) yourself to be under exposed, allowing the flash to make up the rest.

In your specific case, i think you have 2 issues, first, I am not sure the flash supports auto mode (I do not know of any flash except the AF540FGZ and AF360FGZ which do. As a result the flash is probably firing at full power. (Someone correct me here if I am wrong and the flash in question does support auto)

Even if the flash does support auto mode, you cant set the flash to fire and have 100% exposure without flash as this will lead directly to over exposure.
I hope this helps lead you in the right direction

Last edited by Lowell Goudge; 06-24-2010 at 11:38 AM.
06-24-2010, 12:26 PM   #21
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QuoteOriginally posted by Lowell Goudge Quote
corkboard
In your specific case, i think you have 2 issues, first, I am not sure the flash supports auto mode (I do not know of any flash except the AF540FGZ and AF360FGZ which do. As a result the flash is probably firing at full power. (Someone correct me here if I am wrong and the flash in question does support auto)
Hi, Lowell. The AF 280T does support Auto, with two ranges. It also supports TTL, which does not work on the K-X or any later digital flash. It has manual flash as well. The OP is trying to use the Auto mode, and we've been "talking" back and forth to resolve the issues he is having.

Albert
06-24-2010, 01:32 PM   #22
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In AV mode, your shutter speed should be changing based on the focal length of the lens. Something is not working correctly with the flash if this is not happening.
06-24-2010, 01:44 PM   #23
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QuoteOriginally posted by Canada_Rockies Quote
Hi, Lowell. The AF 280T does support Auto, with two ranges. It also supports TTL, which does not work on the K-X or any later digital flash. It has manual flash as well. The OP is trying to use the Auto mode, and we've been "talking" back and forth to resolve the issues he is having.

Albert
thanks, I wasn't sure that's why I asked to be corrected if it did have a sensor

I recognize he is getting close, and think some of the remaining issues are understanding flash.

Clearly if he is setting exposure for the full scene, any amount of flash will lead to over exposure to some extent especially whites, like a fridge. it also depends upon what the flash sensor sees overall, since whites in general are 2-3 stops above grey and if the remainder of the scene is dark, the averaging of the flashe's sensor coould lead to over exposure.

QuoteOriginally posted by rockmaster1964 Quote
In AV mode, your shutter speed should be changing based on the focal length of the lens. Something is not working correctly with the flash if this is not happening.
This is true for lenses that report focal length, but not for lenses that do not, in the latter case, the camera always shoots at flash sync speed if it recognizes it is in flash mode. Not sure how it does that with the flash in question here.

06-24-2010, 02:57 PM   #24
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QuoteOriginally posted by corkboard Quote
Hehe I'm trying not to get too frustrated - the first few days was like this:

I guess I'm trying to figure out a reliable systematic way to take fewer test pictures and understand the results that I'm going to get before I hit the shutter release button. I think at this point I've got to keep testing and build experience

You guys have given me some good rules of thumb to start with at least =)
The basic problem you described in previous posts in this thread is, that you use Av mode and allow long shutter speed sync. That's is basically fine, but if you get 0.5s expsoure times (as you wrote above), you will get a mixture of completely blurred ambient light background and an overlay of the sharp flash image.

Also, if you rely on Av some brighter parts in the background, which do not contribute much to the lightmeter's readout, will get blown (as the white fridge or whatever, you mentioned in one post).

The 280T (as any other flash) will only switch the camera to sync speed in Av mode, if you disable long shutter speed sync.

In my experience it is a good practice, to use flash with M=manual mode on the camera. Set a shutter speed, which will give you some ambient ligt, but is short enough to prevent excessive blur. The flash will then do the rest.

Ben
06-24-2010, 03:28 PM   #25
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Hi corcky, I just bought a K-x, and one of the reasons was that I already had the AF280T. I haven't had too much experiance with using the 280 on the K-x but after reading your concerns I thought I'd give it a try.

My K-x came with the 18-55 kit lens, and I don't see an "A" on it. As a matter of fact it doesn't even have an aperuture ring. In one of your postings you say that you set the lens on "A". What kind of lens do you have?

I tried the flash with the camera set to "P" mode and it worked fine. My white fridge was properly exposed at both the 18 and the 55mm end with the flash was set to auto red or auto green.

I also tried the flash with the camera set to "Auto". Here I did find a quirk! With the camera set to "auto flash" I got an overexposed fridge in both the red and green auto settings on the flash. However when i swithched the camera setting to "flash on", I again got proper exposures with the flash set to auto red or green.

In all the above testing, the flash was at the horizontal position.

When i set the flash head in any of the higher positions (i.e. bounce flash) my shots tend to be underexposed. It's not a big problem, because I could use the EV compensation, but I can't understand why this happens. Anyone have any idea?
06-24-2010, 07:43 PM   #26
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I don't have a K-X but have the K200D and K20D and started off using the AF280T flash (which is great by the way!).. I may not be able to explain all the technical details with regards to using a flash but here's what I've learned from just plain ol' taking lots of photos:

Keep that flash in either Auto Green or Red.. Green gives a more powerful flash and I find that's what I tend to keep it on, especially because I always bounce the flash off a ceiling or wall so I need more power to produce enough light (ie. the light has further to travel as it needs to go from the flash, reflect off a large surface, and then bounce back to my subject).

Shoot in manual mode so you can independently adjust each setting to obtain proper exposure.. of course, you need to understand how each setting affects exposure.

ISO will affect how sensitive your camera is to the flash as it is fired. Higher ISO = brighter picture.

Shutter speed affects how much ambient light your camera will capture. Keep it 1/180 or slower as the flash will not fire above that speed. Higher speeds = less ambient light. You may have seen club photos where only the people close to the camera were exposed while the background behind them is pitch black.. that's what happens with flash + high shutter speed and imho those pictures don't look very nice as you lose the ambiance of the location. The opposite to that effect is when you "drag the shutter", or use a very slow shutter speed (around 1/15 or slower I think) to purposely create light trails from the ambient light (the initial flash will freeze your subject in the image so it'll look sharp but other sources of light will be streaked on the image if you move your camera during exposure).

Aperature will affect both (as well as depth of field). The larger your aperature (small f number.. ie. f1.4 or 2.8), the more light your lens will let into the sensor. When shooting flash I prefer to keep it between f5.6 to 8.0 as I find it's easier to balance the different light sources with those aperatures.

I don't pay TOO much attention to the exposure meter when I have the AF280T mounted because your meter gives you the reading WITHOUT taking into account the effect of the flash. That's why when you were doing test shots and trying to get it exposed properly with the meter, you were getting OVER EXPOSURE once the flash fired.

These days I have an AF540fgz flash that's much more automated so I tend to worry less about getting proper exposure.

Hopefully what I've written is understandable.. and if anything is incorrect, another forum member who's more knowledgeable than I can correct it.
07-02-2010, 07:12 PM   #27
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Check the flash mode on the camera

I just had the exact same issue (K-x + AF280T). It worked fine for a while, with the flash on, in A mode I would set the aperture based on the slide and the shutter speed would adjust based on the focal length (1/25 or 1/80) and maybe the green/red mode of the flash (not sure). Yesterday, the meter would read between 1" and 5". I remounted the flash, turned off and back on everyting, same pb. I know it used to work so I was looking at the setting... Flash exposure on the camera was dialed down (unlikely root cause but...)-> Reset = same thing. Then I see the flash mode, slow sync! I change it to manual discharge and BINGO, I had the correct exposure!
I guess the slow sync mode is not supposed to work with an auto flash...

PS: This is my first post, I thought I had to jump in and share my findings.
07-03-2010, 02:12 PM   #28
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QuoteOriginally posted by jeanpascalc Quote
I just had the exact same issue (K-x + AF280T). It worked fine for a while, with the flash on, in A mode I would set the aperture based on the slide and the shutter speed would adjust based on the focal length (1/25 or 1/80) and maybe the green/red mode of the flash (not sure). Yesterday, the meter would read between 1" and 5". I remounted the flash, turned off and back on everyting, same pb. I know it used to work so I was looking at the setting... Flash exposure on the camera was dialed down (unlikely root cause but...)-> Reset = same thing. Then I see the flash mode, slow sync! I change it to manual discharge and BINGO, I had the correct exposure!
I guess the slow sync mode is not supposed to work with an auto flash...

PS: This is my first post, I thought I had to jump in and share my findings.
Slow sync - that's what I wrote above. It works with Auto on the flash, but you need to know how! Then it makes sense to use it that way. In this case, the camera will expose the image completely independent of the flash and tries to get the exposure right with a long shutter speed.

Ben
04-25-2012, 01:01 PM   #29
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OK...I am going to ask a very, very basic question. I'm not 100% sure how to use the red and green lines on the back of the AF280T flash. Do we set the proper ISO on the slide, and then only use the values between the W and T indications on the red or green band, depending on which Auto setting you use? The lines extend beyond the W side in each case. How do we interpret that? Is that still supposed to be a usable range?

Thanks
04-25-2012, 01:14 PM   #30
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I use this flash with my K7. I found it most comfortable to set the camera to SV and the flash either to red or to green mode. The camera recognizes the flash and if it is in red or green mode. You just have to set the ISO and the camera automatically sets the shutter speed and aperture.
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