Canon EOS 10D

Hi again Andi and other intersted Canon EOS-10D owners.

With respect to the question whether TTL photography is possible with the 10D connected to standard Sea and Sea YS duo strobes via a sea and Sea Canon Hot shoe connecter ( made for either the Sea and Sea CX600 orCX603 Canon SLR housings) and N5 bulkhead strobe connectors, I would like to add the following information. After several more hours of testing I have found the following:

1. TTL DOES WORK when the strobes are set on TTL settings. The strobe light is quelched to provide perfect exposure at all F stops tested . I varied the ambient light for a given exposure setting as suggested by Andi and it works. It works in P, TV, AV and M modes. It works with shutter speeds up to 1/250 sec! Faster than that the curtain becomes visible.

2. The strobe's ready light works as usual. The strobe's green TTL confirmation lights up with TTL exposures. The strobe's TTL beep sound works with TTL exposure. The strobe icon in the camera viewfinder does NOT come on when a strobe is connected ( apologies for me stating this incorrectly in a previous post) The Camera's EXIF information says NO STROBE although the picture is strobe exposed.

3. Flash eposure compensation works.

4. I do notice that the strobes in the TTL mode do not potentially put out as big a dump as when the strobe is in the manual mode. For example at f22 the strobe may give an underexposure in the TTL setting whereas the manual mode can correctly expose or overexpose from the same distance. In other words a TTL flash cannot reach as high an output as a manual setting. I am not sure if this a normal function of the strobes or not but I suspect it is.

5. Andi, I will try to get this all together in a format with the actual pictures with EXIF information attached and EMail it to you or anyone else who is interested as soon as time permits.

Unfortunately I dont think I am going to get this issue resolved in time for my Fiji trip so I will probably be shooting manual exposure but I will keep you posted on future developments.

Cheers, Andre

Hi Andre,

This is very intruiging, I will try my 10D in my Subal housing for the EOS A2e tonight and see what happens. Does the S&S setup have any circuitry in the housing? My Subal has a circuit board for that....

Stu

Hi Andre,

 

This is very intruiging, I will try my 10D in my Subal housing for the EOS A2e tonight and see what happens.  Does the S&S setup have any circuitry in the housing?  My Subal has a circuit board for that....

 

Stu

There appears to be some circuitry in the Sea and Sea housing. There is a small black box ( maybe it records events if the camera drowns ) about 0.5 x 4 X 2 cm which seems to distribute the hot shoe information to the two strobe bulheads. It is sealed so I cant say anything more.

Possibly the hotshoe connector itself may have circuitry as previously posted by martys ??

Good luck

4. I do notice that the strobes in the TTL mode do not potentially put out as  big a dump as when the strobe is in the manual mode. For example at f22 the strobe may give an underexposure in the TTL setting whereas the manual mode can correctly expose or overexpose from the same distance. In other words a TTL flash cannot reach as high an output as a manual setting. I am not sure if this a normal function of the strobes or not but I suspect it is.

OK I will give you the latest.

I had some Email correspondence with Uwe from UK about the issue. He tried doing the same thing as I did. He seems to think that the overall reduction of flash light in the TTL mode is significant. I will agree that it is considerable - the YS 120 strobe gives off a maximal dump in TTL that is about the same as what you will get with the strobe in 1/2 manual mode. Unfortunately I dont have a flash meter to accurately quantify this

So while a mode of TTL is working with this setup that does prevent overexposures ( and this part works very well indeed - even the lagest lens apertures and slowest shutter speed combinations give perfect exposures due to TTL strobe quelching ) , it may unfortunately cause some underexposures where you need lots of lflash output with small apertures. Now of course this can be worked around by decreasing strobe to subject distance or by changing the ASA. I did get a propper flash exposure at F32 but the strobe had to be about 6 inches from the subject with an ASA of 800. But of course this is in air , not water.

Is this then worthwhile persuing? I am still inclined to think so as I can see it being useful in many situations to prevent overexposures. And if not you can always simply turn the strobe/s back to manual mode and do the current thing.

For now it seems that I am going to get my housing with the regular setup. Perhaps I will easily learn manual exposure and not miss TTL too much ??

5. Andi, I will try to get this all together in a format with the actual pictures with EXIF information attached and EMail it to you or anyone else who is interested as soon as time permits.

Hi Andre,

why don't you attach shrinked images to your reply in this forum? the IMG button

should do fine for that. Looking forward top see a pic of your assembly B)

Andi

Looking forward top see a pic of your assembly   

 

Andi

Hope you can see this. Still trying to figure out how to post the actual pictures with EXIF . They are ready to Email though

So while a mode of TTL is working with this setup that does prevent overexposures ( and this part works very well indeed - even the lagest lens apertures and slowest shutter speed combinations give perfect exposures due to TTL strobe quelching ) , it may unfortunately cause some underexposures where you need lots of lflash output with small  apertures. Now of course this can be worked around by decreasing strobe to subject distance or by changing the ASA. I did get a propper flash exposure at F32 but the strobe had to be about 6 inches from the subject with an ASA of 800. But of course this is in air , not water.

Hi Andre,

I've been watching this thread with some interest, since most dSLR's and certainly all the Canon prosumer series, D30,D60,10D, just don't have a sensor which could give true TTL quenching signals, the CMOS surface just doesn't give reliable diffuse reflection required for that.

Now reading your latest description of the behaviour it sounds like the TTL mode on the Sea & Sea units is responding to some spurious quench (note spelling) signal generated by the CX603 circuit. This is shortening the flash and preventing overexposure within the range of apertures and strobe-subject distances that you are testing.

Beyond that you are providing additional "TTL" functionality by moving the bottle in the case of f/32 that you mentioned.

If I am correct, then in this case: f/32, 6 inches, ASA 800, where your TTL mode is providing JUST enough light, then if you switch the strobe to full power manual, then it will overexpose. If TTL were really working, then in this case it would already be providing full output.

Bear in mind also that shutter speeds are irrelevant to strobe exposure, unless they are too short for the curtain to avoid masking part of the image.

Now I may be completely wrong and you have a small black box of deep voodoo magic in the CX603, and I would really like that be the case as I'd love to be able to use TTL on Standard S&S strobes, but I think the explanation is something similar to what I've described above.

Hope that helps

Martyn

Hi,

I just tested my 10D by plugging it into the bulkhead of the Subal CE5 housing for the Canon EOS 5/A2e film camera and then using my twin YS120's

Basically, what is happening is what Martyn said, the circuitry sends an early quench signal to the strobes, it just so happens that the quench is within the exposure range of the sensor. The strobes then use this quench signal as a trigger to the TTL confirmation lamp. Each full stop change in aperture shows a progressively dimmer subject. Setting the strobes in Manual mode (either full or half power) results in grossly overexposed shots.

This early quench signal also happens when the lithium battery in the translator curcuitry runs down. You'll end up with just a small spurt of light from the strobe, my guess it's at about 1/8 power.

It was worth a shot, but I guess if anything, this shows the exposure lattitude of the CMOS sensor in the 10D. The images at F22 could have been easily restored exposure wise, especially if it was shot in RAW mode. Also, I believe the 10D has a "Safety Shift" mode that will let the camera adjust for overexposure in TV or AV mode....it's CF 14, I think.

Guess we're back to using the strobes in Manual mode or housing the 550EX.

Stu

It was worth a shot, but I guess if anything, this shows the exposure lattitude of the CMOS sensor in the 10D.  The images at F22 could have been easily restored exposure wise, especially if it was shot in RAW mode.  Also, I believe the 10D has a "Safety Shift" mode that will let the camera adjust for overexposure in TV or AV mode....it's CF 14, I think.

 

Guess we're back to using the strobes in Manual mode or housing the 550EX.

 

Stu

Ok we will let it RIP!

Thanks to all for your inerest and comments.

So I will see how I will get along in the manual mode on my trip to Fiji and report back to you. I still think that if I have a problem with flash overexposure for a particular shot I will simply set the strobes on TTL

Too bad the CF 14 doesnt work with our strobes either Stu.

Ok, a new question. Has anyone tried the new ( 3rd generation ) Sea and Sea YS 90 Auto strobe? Would like to hear opinions on the usefulness of it.

Andre ( the poor one remember! )