Black stripe in AV-1 photos

[bob_miller4]

<p>Yesterday, I shot some photos with a Canon AV-1 camera with an old Vivitar thyristor flash mounted on the hot shoe. The shutter was set to 1/60 sec for flash. A few of the pictures had a mainly black stripe at one end of the frame, but most were perfect. Where the pictures were shot in landscape mode (horizontal). the stripe was at the left end of the print. Within the stripes, some highlights could be seen, as if the shutter was open but the extra light from the flash was absent. Does this sound like a flash synchronization issue associated with either the flash unit or the hot shoe connection? Thanks for your guidance!</p>

 

[howard_m]

<p>certainly sounds like a synch issue. maybe some sort of contact corrosion over the years is making it intermittent? perhaps the timing of the shutter is variable and it's right on the edge of what works. maybe the flash is having issues (not fully charged between shots so it's running out of 'gas'), weak capacitor etc etc. it's not unusual for a flash to require a slightly longer synch time than the camera maker advertised.</p>

[gordon_yee]

<p>Another possibility is that you were using a wide angle lens with a field of view slightly wider than the coverage angle of the flash. What flash unit and lens were you using?</p>

[bob_miller4]

<p>Gordon,<br>

I was using a 35-105mm zoom and I had considered the possibility that the flash only properly covered focal lengths longer than 35mm (or whatever). But this raised questions: <br>

1. Wouldn't the light intensity fall off gradually outside the flash's "good zone", as opposed to very abruptly? With 28mm lenses, I've used flashes meant for higher focal lengths, but still got a decent amount of light along the edges.<br>

2. Why would the black stripe be only on one side of the frame, and consistently on the same side? </p>

[walter_degroot]

<p>if the cut-off is clearly defined it is mechanical.<br>

First exercise the camera by winding and shooting many times while it is empty.<br>

when the flash fires all energy is discharged to the flash tube.<br>

if the capacitor was not properly of fully charged the circuit wouild not let it fire<br>

but if the flash did manage to fire without being fully "recycled"<br>

the result would be less light and the time would not change.<br>

a modern Thyristor flash does indeed send out a shorter burst of light<br>

if the sensor sees the subject is close., but that short burst is instantanious.</p>

<p>the X synch means the flash fires when the focal plane shutter is fully open.<br>

so a minor malfunction of the movement of the shutter curtains is indicated.</p>

[gordon_yee]

<p>If it's a synchronization problem and the dark stripe is only on the left side of the frame, it would indicate that the second curtain is starting to close just before the flash is triggered. You could try testing your camera (with no lens attached) by pointing it at an evenly lit light colored wall and triggering the flash while looking through the back of the camera. Try using shutter speeds of 1/60 and 1/30 and see if the the dark stripe can be detected.</p>

<p>Is your camera starting to show signs of the A series squeak? This is only speculation, but I wonder if the lubrication problem with the flywheel and damper mechanism that governs the operation of the mirror may also affect the flash synchronization.</p>

[mwmcbroom]

<p>The A-series squeak affects mirror operation only. It does not affect the shutter's operation at all. Flash sync is governed by a set of electrical contacts associated with the shutter, not the mirror.</p>

<p>At flash sync, or slower, the first curtain opens fully for the 1/60 second or whatever, then the second curtain closes. At speeds above flash synch, a slit of varying widths, depending on speed, exists between the first and second shutter, and travels from left to right across the film plane. In your case, it sounds like the second curtain is starting its travel too early, especially if you can still see some subject detail in this dark band. Does the detail vary from the right to the left of the dark band? Is there more detail along the right edge than the left? If the band shades darker to the left than the right, this suggests movement of the second shutter while it's out of position, rather than it just moving out into this new position, sitting there, then closing.</p>

<p>The shutter timing is all electronic on the A-series Canons, and I believe it's governed by a set of electromagnets. I would suspect the electromagnet(s) controlling the second shutter as being the most likely culprit.</p>

 

[bob_miller4]

<p>Michael,<br /> <br /> Yesterday I shot over 48 pictures with the same camera and flash. Of these, only four (two well-separated groups of two), showed the dark band. No squeal was heard. Per the flash instructions, I left the lens aperture at 8 and let the thyristor adjust the exposure, which it did well in three of the pictures with dark band (in the fourth, a foreground object made the flash cut off too quickly, so there was underexposure of the main subject).<br />I could see some highlight detail in the dark band, sometimes evenly across the width of the band.<br /> I also shot over 20 pictures with the same camera and no flash, using the aperture priority shutter automation, and no dark bands appeared on any of these.<br /> Could your hypothesis account for the above and also the intermittent nature of the problem?</p>

[awahlster]

<p>It is time for your camera to be Cleaned Lubed and Adjusted by a competant camera repair tech.<br>

Many if not most of these 30-40 year old cameras have never seen a tune up or adjustment in their life time. And just like an automobile you will be amazed at how far and long you can drive some cars without any tuneups but they are not working at their best.</p>

<p>If you enjoy the camera the money is well spent. A good CLA can add a decade to even a neglected body.</p>

[bob_miller4]

<p>Mark, what tech would you recommend in the Midwest (such as Indiana) ?</p>

[walter_degroot]

<p>Michael's pst is more direct and to the point t<br>

than mine. I am sorry if I mentioned other things.</p>

<p>I talked about the flash. when I shiuld habe stuck to the mechanical issues.<br>

I t is possible he camera has not been "exercised"<br>

recently, that all it needs is some winding and clicking.<br>

the proper response would be to get a good CLA.<br>

But a $75 dollar CLA on a $25 camera makes no sense</p>

[gordon_yee]

<p>If only two exposures had the dark band, I'd doubt if the camera's flash synchronization is at fault. If these two exposures were shot at the shortest focal length of 35mm, it could still be a flash coverage problem, light falloff, an obstruction of some kind, a defective lens on the flash head, etc. With the limited amount of information at hand, we're kind of shooting in the dark, so to speak.</p>

[mwmcbroom]

<p>Gordon, it isn't the flash synchronization per se that I was referring to, it is the timing of the second curtain. And the release of the curtain is determined electronically, controlled by a set of electromagnets. I'm not an expert here, but I have read that sometimes these magnets can get coated with lube that migrates down onto them from other areas of the camera, which leads to erratic behavior, and which is specifically what Bob is experiencing. Sometimes all it takes is a good cleaning of their surfaces to restore them back to spec.</p>

<p>However, as I sit here thinking about this, I wonder if there might have been a way for the precise time at which flash sync occurs to have been moved. If this time is moved back such that it is almost coinciding with the second curtain's release, then I can see how this might be causing the problem. Only thing is, I've never heard of the instant of flash sync being adjusted or moved.</p>

<p>Bob, I would not expect to see the banding in photos in which the flash was not used, especially if the photos were taken at speeds above flash sync speed.</p>

<p>I agree that a $75 CLA makes no economic sense for a $25 camera. But chances are good that any other of the $25 cameras out there just like this one haven't been CLA'd in decades either. So even replacement doesn't really represent that good of an option. It might very well be the replacement will work flawlessly for years, but it is a crap shoot. Sometimes you gets lucky, sometimes you don't.</p>