430EX not detecting sensor size on 20D

<p>I just bought a secondhand 430EX and it does not seem to be properly zooming for the sensor size on my 20D. Regardless of the setting of C.Fn 3, it displays the focal length the lens is set to, rather than the 35mm equivalent. I'm using the 17-85 IS, if that makes any difference.<br>

All other flash functions work correctly, and the flash zooms properly when fitted to my G9. <br>

This doesn't seem like the behaviour indicated in the manual; am I doing something wrong? </p>

<p>(I searched and searched, both the web and photo.net, and nobody else seems to be having a similar problem--or, if they are, they are all silent.)</p>

<p>Not sure what you mean, the flash doesn't "adjust" for the sensor size, it just shows what the lens is zoomed to. So, if your 17-85 is set at 50mm that's what will show. It doesn't multiply by 1.6 to give you 80mm if that is what you are expecting.</p>

<p>That <strong><em>is</em></strong> what I'm expecting, both because that's what C.Fn 3, "Auto zoom for image size" is supposed to do, and because that's how it behaves on my G9--which most DEFINITELY doesn't have a 105mm lens on it. ^_^</p>

<p>Anyone know the skinny on this?</p>

Mark, I get the same result as Mark S. with my 40D and 430EX. But, I hoped it would behave as you expected since it makes more sense. After all, why light a field of view that's wider than what you are photographing? Your getting coverage but some output is wasted. Also, I can't seem to access the flash custom functions despite the 430EX being attached and powered on. I'll have to see what I'm doing wrong.

<p>Right around the time that the 430II came out, Canon made more sophisticated algorithms to account for different sized sensors. I'd have to check to see if the 430I was designed to do this. In any case, it's a minimal issue that will have little practical application for normal use. You've got yourself a great little flash.</p>

<p>I have both the 430EX and 430EXII, both will adjust for crop factor. With the 17-85mm lens you will not "see" it do the adjustments to the zoom of the flash head to the zoom of the lens, unless you take into account that at 17mm the flash does not tell you that there is not enough coverage. If it were on a full frame camera 17mm is beyond it's view, 18mm is capable <strong>if</strong> you pull the diffuser panel down.</p>

<p>Rack your lens to 17mm and don't flip down the wide angle diffuser panel. Take a shot. Does the flash say that it can't handle that width? The display will flash the zoom length (24mm). If not, and it's not severely dark at the edges then the flash is working properly. It does the calculations and doesn't try to confuse you by giving you a different focal length than what you have on the lens.</p>

<p>From what you are saying I would suggest that it is the camera that is at 'fault' not the flash as it should be telling the flash that it is a crop camera.<br>

My Simga equivalent flash does exactly the same thing when fitted to my 20D and my 40D. You will just have to get used to it!</p>

<p>I've used a 430EX since 2005 and, left on autozoom, it zooms with the focal length. Coverage matches that of FF (makes sense as it was originally released as the kit zoom for the EOS 5). It doesn't reduce coverage for 1.3x or 1.6x sensors. I see this as a feature on APS as a wider spread of light tends to bounce around more, making for a slightly nicer quality of light. On FF I usually adjust the zoom head manually for a wider spread.</p>

<p>Okay Mark, I was unaware of this feature, I just checked the CFs for my 580EX and CF 11 apparently does this, cool. Can anyone say whether this is worth using, does it make a substantial difference when using crop sensor cameras? I have the 20D/40D. So will this "reduce" the about of light the flash emits to compensate for the "closer" field of coverage? I would think the sensor/pre-flash would do this anyway, maybe this changes the algorithm somehow? Not trying to hijack the thread but would be interested in real world experience with this feature, had not heard it discussed before.<br>

Thanks</p>

 

<p>Mark Sandserson. The zoom of the flash head utilizes the light more efficiently. I'm sure you're aware of that but just to say it so that anyone else reading is confused:<br>

The zoom of the flash head is designed to cover the angle of view of the corresponding focal length of the lens. i.e. if you have a 50mm lens on the camera you don't need to have as wide a field of light from the flash. Everything on the edges would be wasted light. Zooming the flash head to just cover the lens means that you can also throw light further. So by default using the zoom would conserve your flash's batteries.<br>

-<br>

Consequently most flash's advertised guide numbers are stated for the maximum flash's zoom. The 430EX for example claims to have a guide number of 43 meters. But to achieve that at ISO 100 you need to be at a zoom that covers 105mm. At 24mm coverage (the widest the flash goes without the diffuser panel) you're only at 25 meters, almost half of the stated guide number. At 14mm coverage it's only a guide number of 11 meters.</p>

<p>Puppy Face, the 430EX does take into account your sensor size. Page 21 of your manual. Automatic Setting of flash coverage for camera's image size. It says that it will automatically set the zoom for your camera's sensor size. Page 33 also states <em>"flash coverage - Auto zoom (flash coverage set automatically for lens focal length and image size)"</em></p>

<p>Dan, does that mean the 430EX flash is told by the crop camera a different focal than is actually being used? Or does the flash adjust it's coverage to a smaller area knowing the camera is a crop camera? My flash has a focal length indicator that shows the same as my lens focal length.</p>

<p>Jeff, you can hear your flash head adjusting as it zooms correct? So if you set your lens to 24mm you should hear it zoom somewhere and the display will say 24mm. All fine and dandy, doesn't prove a thing yet. Put a wide lens on camera (17-85, 18-55, whatever) and set the lens to lower than 24mm. Does the flash head zoom when you take it from 24mm - 18mm? Does your flash not flash the display (430EX or EXII)? Then it's saying that it's covering 18mm, which if you figure in the crop factor works out to 24mm, what the flash can handle without using the wide angle shield.</p>

<p>Let's work on it from the other end. Put a lens on the camera that goes past 105mm, but goes bellow 80mm. The 28-135 would work for this if you have one. Set the lens to 28mm, then as you zoom up to 80mm you'll hear the head zooming. Past 80mm you won't hear the head moving. That means that at 80mm it stops (even though the display says 80mm and 105mm at those focal lengths). Put that same lens on a full frame camera (who doesn't have an EOS film camera lying around?) and try it again. 80-105 mm does move the head this time.</p>

<p>Wether it's the camera doing the math, the flash, or both I don't really know. I just know it works. I assume that the camera tells the flash what kind of crop factor it is and the flash compensates. All I know is that it works like it's supposed too on my XTi, 40D, ElanIIe, and my Rebel film camera. I guess it is possible that a 20D may not give the sensor size to the flash. My 1D (first 2001 version) doesn't appear to do this, it's a recent purchase and I just checked it out with a 28-135 and a 430EX (first version).</p>

<p>Lot of good responses. My 430EX works beautifully on my 20D, I couldn't possibly be happier with it. I just thought it was odd that they included a feature to compensate angle of coverage for sensor size if it doesn't actually work. Stranger still is that it works as advertised (tracks FF-equivalent focal length) on the G9 point-and-shoot but not on the 20D semipro SLR!</p>

<p>My 380EX did the same thing, so my guess is that the 20D does not report FF-equivalent focal length through the hotshoe, or doesn't know how to tell the flash what sensor format it has. After all, I suppose, the G9 was introduced a couple years after the 20D...</p>