Cobra 700AF flashgun and old digital Canons

[Farside]

A couple of years ago I bought an old Cobra 700AF flashgun, complete with side-bar mounting kit. It cost a tenner and I didn't expect it to work with the digital bodies, except in fully manual mode. Sure enough, it didn't, but I wasn't disappointed. I only wanted it as a fully manual flashgun anyway.
Anyway, roll on to this week, when another 700AF arrived for my film Pentax bodies - this time I expected it to work with them, as that's what it was designed for.
It worked, then it didn't work, then it did, and didn't.
Hmmm... dodgy contacts - sorted them out and then tried it on the Canon flashbar that came with the first Cobra - no use, it wouldn't work. The flashbar assembly is designed to work with any 700AF Cobra, it's camera-independent, just an extension, essentially.
This got me thinking - there's a connection fault with the flashbar assembly. So I assembled the Canon-fit 700AF without the flashbar and stuck it on the Canon 10D, set the camera in Program (green square) mode and tried it.
B888er me - it worked fine on full auto
It's sensing the light coming back, the camera is cutting off the flash and it's illuminating things properly indoors and out. These weren't full-power bursts, they were definitely short ones, under control of the camera. Bounce mode is working fine and the red illuminator for focus aid is also working as it should.
So, it seems to be working in E-TTL mode, as Canon flashes should and what I've always read is that Canon film flashes won't work with digital bodies.
It would be interesting to see if a Cobra 700AF would work with later Canon digibodies - as far as I know they're the same flash standards and if it works on mine, it shoud work with later ones.


The Pentax K10D won't talk to the 700AF-Pentax flash though; but I already knew that - or did I? Watch this space.

[Farside]

Further investigation reveals:
1. In 'green box' program mode, the shutter speed is 1/60th and aperture is 4.5 or 5.6, depending on where the zoom is set. In other words, the camera is setting the lens wide open - but some flash control is happening because each flash duration is short - such a shutter/f stop combo would obliterate the picture and while they might not be perfect they're reasonably exposed, perhaps a bit on the light side.
2. In 'flash' mode there's an even better control of the light output - the only problem is that the shutter speed auto selected is around 1/2sec and that's not much cop. Well-lit results are got and whether the flash head is swivelled or bounced, it still determines the right amount of light and cuts off the flash when enough light gets back to the sensor. Unfortunately, you have to hold the camera rock steady for the remaining exposure time.

So... there's some sort of communication going on and it seems to be partial E-TTL. According to Canon the old TTL system was discontinued and there's no facility to read reflections off the film/sensor any more. I don't know exactly what pathway it's taking, but something's reading the flash incoming light and communicating with the flash head to cut it off at the right time.
Also, in 'flash' mode, when the gun has gone off there's an 'auto' confirm light appears on the back of the flash head to tell you it's all gone fine. If it wasn't for that pesky slow shutter speed, I'd be happy enough with 'flash' mode.

[Farside]

Right; further investigation reveals...
1. In 'green box' mode during daylight and darkness, the flash is controlled, but the shutter speed is still fixed at 1/60th and the aperture depends on the AF lens fitted. I tried with an 18-55mm f:3.5/4.5 and a 28-105mm f:2.8/4.0 and as the zoom length changes so does the maximum (widest) aperture - this is what the camera selects for the shot. So, in summary, it works ok, but can sometimes be a bit blown out. Ok for night shots with little or no ambient light.

2. In 'flash' mode, the camera sets the shutter speed according to ambient light (this is what was giving me the itch) and the flash is simply there to illuminate and fill in.
The aperture, once again, is fairly wide.
It works rather well in this mode - it's just fit, fire and forget. The camera takes care of it fairly properly with an even spread of illumination - and doesn't blow out backgrounds, only lighting enough of the subject to show it properly. Great for back-lit subjects, as I've no doubt Canon intended.
There is one drawback - it's not possible to change the aperture in either of these modes, so what you get is what you get. Of course, there's the fully manual option, as always.

Owners of various Canon Speedlites will no doubt think this is old news, but this is the first dedicated flashgun I've put on this old thing (previously, just used an old thyristor gun, which worked well enough) and I'm fairly pleased at the results.

So - there we have it - pick up a Cobra 700AF for your old Canon and save a fortune on Speedlites. However, there's a caveat; as I said above I do not know if the 700AF will work on later E-TTL Canons. Canon chop and change things in an effort to keep the upgrade market to themselves, so who knows.

Oh by the way, there's one thing I should mention - the hotshoe voltage is 4V, so perfectly safe for all Canon models.

[kansalliskala]

Thank you for all info.

Now some day when I decide my Metz 45 is too small I can turn to the Cobra family.

[Farside]

I was seriously thinking of a Metz 45 recently (I've always fancied one of them and the modularity appeals to me), which prompted me to dig out this old Cobra, just to see if it would work.
Anyway, after seeing the sun out today, I went and took some backlit shots using the Cobra/Canon combo and it's working well. I don't need any better flash than this (GN35) for the Canon and all I need now is some degree of automation for the Pentax.
There's a shortage of cheap old auto-flashes for Pentax that will work on digibodies, and I prefer a bracket type of flashgun anyway, which made me look at the Metz.

[martinsmith99]

That's good info as you can usually pick these up for peanuts and GN35 is fine for most uses..

I have 2 big Canon flashes for my 5Dii, but on other cameras I like the Auto modes of the Vivitar 285 & 283; they're difficult to beat for power.. I also think that the Nikon SB-28 with auto, manual & strobe modes, is great for any system.

One thing to watch is that the early Canon DSLRs don't like high trigger voltages that some old flashes can have.

[Farside]

I'm stil mystified as to why I'm getting some cut-off control from the camera. Canon said this wouldn't happen and yet it's working quite distinctly in two modes - 'green box' and 'flash'. I'll get a full power flash if I put it into Av - the shutter speed is synced at 200 (which I set in custom) and I can rapidly spin the aperture button to f:19 or so for greater depth of field - so that's not too bad and provides usable results.
I wish I knew what the control path is - it's not simple TTL, but there's some sensor in there crying 'enough' and shutting the flash off.
It's not perfect - some of the Program results are a bit under, but the daylight fill mode seems to work really well.
If I could get the Pentax working as well as this, I'd be quite happy.
It's not that great with a manual lens on - more or less back to manual flash set up, but I expected that, so no big deal.

[martinsmith99]

I'm mystified Dave.

What happens with a manual lens? My Canon flashes don't seem to care what lens is attached and that's what I expected, but are you saying it will not meter at all without an EF/EFS lens?

[Farside]

I tried a manual lens with and without a focus confirm chip.
Without the chip, with no beep the flash just goes to full power. With the chip, the camera is told the aperture is f:2 and the picture is overexposed.
Totally manual usage is still fine of course, so it's just like the 1970s.

Anyway, it works well with an AF/EFs lens and will do for occasional flash purposes, especially outdoor fill, where it really shines.

Also, mention of the Metz 45 re-awakened my interest and I've just scored an old 45 CT-4, and found someone selling a set of Pentax adapters and cords fairly cheaply, along with an external trigger sensor.
This will do for the K10D and other Pentaxes, now and future - lovely thing about the Metz kit is the expandability of it and all the modules means it never goes out of date.
The whole concept of the SCA 300 - 3000 system is excellent and it's been around long enough that bits are readily available for not a lot of money.