450D strange exposure metering

[michal_urban2]

<p>Hi,</p>

<p>Ive got maybe a stupid questin regarding my Canon 450D (with 18-55 IS).</p>

<p>The camera is on tripod in my room, light condition do not change. Now, when not using the integrated flash, all the modes (P, A, T) meter the same shutter speed and aperture.</p>

<p>But when I try to use the integrated flash, the P mode says the right combination is f/4 and 1/60 - when I use A mode and set f/4 camera says time 1/6 - and when I set 1/60 using the T mode, the camera tries to set such a large aperture it is not possible with my lens. The P mode metering is right btw, with A or T the picture gets overexposed.</p>

<p>I have no idea what to do ... please, help! :)</p>

 

[MarcelRomviel]

<p>As far as I know that is how it is with canon flash.<br>

A quote from the EOS flash bible:</p>

<blockquote>

<p>In Av, Tv or P modes, it will attempt to expose properly for the ambient light by adjusting either the shutter speed, aperture, or both. <strong>The fact that you have your flash turned on has no effect on this**</strong> ( one exception is that in P mode it will not use a shutter speed slower than 1/60 with flash).</p>

</blockquote>

<p>You can find the flash bible here:<br>

http://photography-on-the.net/forum/showthread.php?t=138907</p>

[phule]

<p>The flash is not treated as the main light source in Av and Tv modes. Your camera will expose for the ambient light and use the flash for fill. </p>

<p><a href="http://photonotes.org/articles/eos-flash/index2.html#confusion">http://photonotes.org/articles/eos-flash/index2.html#confusion</a></p>

<p>Read the whole section. </p>

[michal_urban2]

<p>I know what it is supposed be doing - but the problem is that the camera makes different exposure for non-changing light situation. When I use P mode, it exposes right, with A or T it exposes wrong (overexposes). And it only happens when the flash is out.</p>

[michal_urban2]

<p>Rob: I will go through it!</p>

[michal_urban2]

<p>Rob: Fine, thank you. But now I dont really understand how can I use the flash the way I was used to - ie. when I had Nikon D50 and was shooting some garden party and it was dusk, I popped the flash out and was shooting - the camera said 1/60s and some f/stop the camera determined. Now I have no idea how to shoot quick action: "<em>If that means the shutter speed is some really low value so that you need to use a tripod to avoid camera-shake blur, so be it."</em><br>

I know I can use the P mode but Im used to shooing in aperture priority for years ...<em><br /></em></p>

[phule]

 

<p>[[ when I had Nikon D50 and was shooting some garden party and it was dusk, I popped the flash out and was shooting - the camera said 1/60s and some f/stop the camera determined. ]]</p>

<p>This sounds exactly like P mode. </p>

<p>[[but Im used to shooing in aperture priority for years ...]]</p>

<p>If you want a shutter speed of 1/60th and you want control over the aperture, why not put the camera in M, and leave the shutter speed at 1/60th?</p>

 

 

[michal_urban2]

<p>Rob: Sorry, wrote the first line wrong. :X What I meant was that I set the f/stop and the camera set the shutter speed (which was usually 1/60th). When it got undera say 1/40, I knew I should decrease the f/number.</p>

<p>Anyway, with the Nikon I saw what speed and aperture is set and a) I knew the camera made the exposure and b) I saw if I can hold for the time. If (with C450D) I set manually my favourite combination (1/60, f/8) with flash on, how can I be sure the exposure would always be right?</p>

 

[phule]

 

<p>What does "always right" actually mean? </p>

<p>Flash being used as fill and flash being used as primary both produce images that are "right" but are clearly different. </p>

 

[michal_urban2]

<p>Rob: Sorry for my english, I wrote it kind of messy.</p>

<p>I guess theres nothing to do with this matter anyway. I understand one can use both fill and primary flash - for different purpose - but all I want is to have an option to set.</p>

<p>Anyway, hope the following could explain the trouble Im having:<br>

-----<br>

When I use the P mode, the metering is ok, but you cannot alter the expozition metered (with flash). There are almost always more then one possible combination of speed and aperture but the P mode unfortunately wont let me choose and forces only one. (When it says 1/125 f/5.6, I could as well say 1/60 and f/11, but its impossible to do so.)</p>

<p>When I use Av, I cannot tell the camera not to use the flash for fill, therefore its unusable for shooting quick action. (I cant really hold 1/6 and using a tripod when shooting a eg. dance is also kind of lame ...)</p>

<p>When I use Tv, I cannot tell the camera not to use the flash for fill, therefore its unusable for shooting quick action. (When I set say 1/60, the f/stop indicator keeps blinking that its unable to set such a large aperture to make correct exposure.)</p>

<p>When I use M all the time (during night), I cannot be sure the exposure would be right. (I set the camera for 1/60 f/8 and it may be ok during the night, but sometimes it would be better f/5.6 or f/11 - and I wouldnt know about it. I though I could use the camera exposure indicator (the bar at the bottom in the viewfinder) but I cannot - when I used the P mode to meter the scene, then set the metered values in M mode ... the exposure indicator told me I was more than 2 ev`s wrong. It was the same scene and same values and it wasnt neither Av nor Tv. And it was still wrong.)</p>

<p>Also, I was thinking about setting the fixed 1/200s sync, then using M mode to set 1/60 and control the f/stops, leaving the camera to control the power of the flash. It works, but its still a bit weird - like I have to remember not to set higher aperture number than circa f/13 and the exposition also isnt always right).<br>

-----<br>

Im sorry for this mess I wrote, Im just confused with the way Canon works in Av with flash and am looking for the best way to to "flash shooting of quick action in darkness" ... With Nikon, there was the flash as a primary light.</p>

<p>THANKS FOR YOUR ADVICES AND LINKS!</p>

[michal_urban2]

<p>PS: I ended up using the M mode - I set the f/stop, the speed and iso and let the flash determine the power. Seems to be the best way to do this ...</p>

[mwtphoto]

<p>M mode is the way to go.</p>

[jstraw]

<p>I agree that M mode is probably the best option, but the metering you were getting doesn't make much sense. If it's supposed to expose for the ambient light when you have the flash on, then the exposure should be pretty similar to what you get when you don't have the flash on, since it's also metering for ambient then. Turning the flash on shouldn't cause all pictures taken in AV or TV to be wildly over-exposed.<br>

I tried this myself with my 450D and got different results. The ambient, no-flash exposure was F3.5, 1/25, ISO 400. I got this in both AV and TV modes.<br>

When I popped up the integrated flash, the exposure changed to F3.5, 1/50, ISO 400. This was indoors in a fairly small room, so the flash lit up everything. The histogram for the photos with and without the flash look pretty similar. I tried with an external 430EX flash and got the same metering as with the integrated flash.</p>

[josh_wolf]

<p>There is a Custom Function "Flash sync. speed in Av mode" that allows you to set the shutter to a fixed speed of 1/200 sec. Thus, you can use the Av mode without camera shake. In newer models, such as the T2i (550D), there is a third option of letting the camera choose a shutter speed between 1/200 and 1/60 sec. However, the manual says that "the background will come out dark."</p>