Flash Issues

[deeky]

Following up from a previous thread.

Using a Yongnuo YN568EXII on a Canon 20D. Flash is firing, but doesn't seem to have any power behind it. Following previous advice, I cleaned the contacts (weren't bad to start) and put in fresh batteries. It has not been used hard at all.

Below you can see the results. Both shot 1/80 f/4. First one is with -2 stops of flash compensation and the second is with +2 stops of flash compensation. It just doesn't seem to have the power it should. With the same ISO, shutter, and aperture, I would expect the second to be blown out compared to the first.

The third shot shows the back of the flash as set for the shots.

Any ideas?

IMG_1176 by breckmiller, on Flickr

IMG_1175 by breckmiller, on Flickr

IMG_0624 (3) by breckmiller, on Flickr

 

[smoke665]

If I'm reading the last picture right, you're using ETTL. Have you tried it on manual? Not familiar with the Canon TTL metering for flash, but found this which might help.

Canon EX Flash TTL, E-TTL, and E-TTL II

 

[Overread]

ETTL means that the flash talks to the camera to get an idea of what power it should output based on what the light going through the lens reads. It works well for fill-flash in general, but can fail or get tricked (much as the meter can if, say, you're taking a photo containing a lot of snow).

Try manual mode*; a 1:1 should give you the flash's full power output and you can dial down from there to suit your situation.


edit * on the flash and the camera. By fixing the settings of your camera in manual mode only changes in ambient light and flash light will affect the exposure; so you can then use the manual mode on the flash to vary the power and see the results.

 

[table1349]

^^^^^^^^^^^^^^^
What they said.

Try reading this: Flash Photography with Canon EOS Cameras - Part I.

 

[astroNikon]

Yup. Put he flash in Manual
Being in TTL the flash talks to the camera to always give a balanced light Output.

 

[deeky]

Yup. Put he flash in Manual
Being in TTL the flash talks to the camera to always give a balanced light Output.

Yes, the camera aims for good exposure, but shouldn't moving the flash compensation up two stops blow out the photo if the aperture, shutter speed, and ISO are identical? Two stops should be 4 times the light which should be a much more discernible difference than what I have here. And everything else I've read tells me that adjusting flash compensation in camera will have the same effect as manually adjusting the flash. It has worked in the past and all of a sudden doesn't.

I'm upgrading to a 70D in a few weeks, so I'll try the flash on the other camera and see.

 

[Overread]

Yes and no - compensation is still only compensating the power that the camera+flash thinks it needs to put out. So if that process selects a very low power then, even with the compensation, the power might still be very low. Furthermore don't forget that even on the same scene the meter can pick up subtle differences in lighting from your framing - so it might be that a first shot and a second shot have slight differences in what the camera thinks the exposure is and thus, again, the flash power can be wrong.

I would have expected to see more difference though so could be something like that is going on - so try it in manual.

 

[astroNikon]

Yup. Put he flash in Manual
Being in TTL the flash talks to the camera to always give a balanced light Output.

Yes, the camera aims for good exposure, but shouldn't moving the flash compensation up two stops blow out the photo if the aperture, shutter speed, and ISO are identical? Two stops should be 4 times the light which should be a much more discernible difference than what I have here. And everything else I've read tells me that adjusting flash compensation in camera will have the same effect as manually adjusting the flash. It has worked in the past and all of a sudden doesn't.

I'm upgrading to a 70D in a few weeks, so I'll try the flash on the other camera and see.

If you are in TTL mode then the communications between the flash and camera is probably going to override what settings you have. that's what it's for .. and "auto" mode for the flash to give the proper exposure.

Also, the difference between the 2 pics could also be white balance. The shadows look very similar so I don't think too much flash difference.

Put the flash in Manual mode, and test it.

 

[pgriz]

The advice you have above is good. Try your flash in manual mode at 1:1 power. Chances are, it will blow out the image. Then try it at (say) 1:4 and 1:16. You will have significant differences between these.

It also matters whether you are pointing the flash forward, or elsewhere (ie, bounced flash).

Finally, at least in Canon flashes, there is a difference between ETTL and TTL modes.

 

[deeky]

- so try it in manual.

Yup. Put he flash in Manual
Being in TTL the flash talks to the camera to always give a balanced light Output.

Put the flash in Manual mode, and test it.

The advice you have above is good. Try your flash in manual mode at 1:1 power.

All right - all manual, 1/125, f 6.3, ISO 400, flash on manual at 1:1, no compensation, mid-afternoon with the windows open. Light enough in the room that we didn't need any lights on. This is what I got.

IMG_1199 by breckmiller, on Flickr

 

[OGsPhotography]

Did the flash fire?

At 1:1 it should nearly fry your eyeballs if you look near it ( dont look straight at it) and you should hear it POP and sizzle a bit. If not, the flash isn't working.

 

[deeky]

Did the flash fire?

At 1:1 it should nearly fry your eyeballs if you look near it ( dont look straight at it) and you should hear it POP and sizzle a bit. If not, the flash isn't working.

Yes, it did flash. Confirmed both visually and in the EXIF.

Thinking further, the ready light on the back is always read. I don't get the green light that should signal ready with full batteries. Another symptom?

 

[dasmith232]

Definitely a mystery here... I have two totally different trains of thought going...

First, in the last picture, with 1/125, f/6.3 and ISO 400, you should have an exposure regardless of the flash. You seem to be defying the laws of physics. Or at least the optics part...?

Second, at the beginning of this thread, you have a picture of the back of the flash unit. Now I have Canon flashes, not Yongnuo. So this might not apply. But the icon in the lower left corner is ... wrong. I'll try to explain. The side view of the flash has "master" below it. That says that this flash will be communicating with other flashes. The lightning bolt that's coming out of the lower part of the flash icon just says that it's wireless. But here's the part that's wrong. There should be three little lines extending from the head of the flash icon. In Canon parlance, the master flash will send out signals to the other flashes, but it may or may not be participating in the final exposure. In other words, it gives out commands, but goes silent for the main shot. This is how you trigger side lighting (for example) with a flash that's sitting in the hotshoe.

The option to turn this off is in the "flash control" menu, where it says "master flash", it needs to be "enabled".

But regardless, I'm still stuck with the first point: there should be an exposure regardless of flash...

 

[dasmith232]

Oops, I'm meant to say "ON"...

The option to turn this *ON* is in the "flash control" menu, where it says "master flash", it needs to be "enabled".

But even this alone doesn't answer the other question...

 

[deeky]

Definitely a mystery here... I have two totally different trains of thought going...

First, in the last picture, with 1/125, f/6.3 and ISO 400, you should have an exposure regardless of the flash. You seem to be defying the laws of physics. Or at least the optics part...?

Second, at the beginning of this thread, you have a picture of the back of the flash unit. Now I have Canon flashes, not Yongnuo. So this might not apply. But the icon in the lower left corner is ... wrong. I'll try to explain. The side view of the flash has "master" below it. That says that this flash will be communicating with other flashes. The lightning bolt that's coming out of the lower part of the flash icon just says that it's wireless. But here's the part that's wrong. There should be three little lines extending from the head of the flash icon. In Canon parlance, the master flash will send out signals to the other flashes, but it may or may not be participating in the final exposure. In other words, it gives out commands, but goes silent for the main shot. This is how you trigger side lighting (for example) with a flash that's sitting in the hotshoe.

The option to turn this off is in the "flash control" menu, where it says "master flash", it needs to be "enabled".

But regardless, I'm still stuck with the first point: there should be an exposure regardless of flash...

Dave, you're the man! I had to actually shut the master off so there is no icon showing whatsoever and having the flash on manual, 1:1 completely blew it out. Flash comp on the camera works again like I was expecting. I'm guessing the flash is only working as a trigger in master mode, so while the flash is only flashing enough to trigger the others, the camera is expecting the slave flashes to provide enough light. Since they weren't there for this situation, there just wasn't enough light for what the camera was expecting.

Thank you! Was getting to the point where I was expecting to be buying a new flash.