ISO on 70D When Using Flash

Here is my thread. I was using my 7Dmk2
https://photography-on-the.net …/showthread.php​?t=1440924

Good info. in there - thanks.

Sounds like you have FLASH FIRING set to DISABLE. Is what you are seeing the ETTL pre-flash?

Flash is definitely going off - though I did learn that I could set to manual or eTTL - need to check that setting. Main lesson seems to be that I will need to manually set ISO for outdoor flash

if your subject is more than 22 feet away, i don't think the onboard flash will really be able to reach them

Bringing up an old thread:

I will be shooting a marching band competition this weekend - trophy presentations will be at night and require flash. The scene will be about the same as this (not my shot):

I wouldn't use the pop-up flash. Those are maximum distance values (so you'll have to crank up the ISO quite a bit and overwork the small flash.....all for a photo with high noise). The guide is saying that's the rated distance of the flash's output at full power: if you have a subject that needs more exposure, then you'll still underexpose. There are 3rd party external flashes, or used Canon speedlites you can buy that will have higher power and light spread: letting you use lower ISOs and better coverage for group photos.

Thanks Dave. Yep, I have to get a decent flash. For this weekend though, prob. will be forced to use the pop-up. Not enough time to research speedlites, buy and learn.

You also have to consider how you want to render the background. If you use Tv (shutter priority) and set the time to 1/125 s, then most probably the aperture will be set wide open. Whether that will give you a black background or something brighter, that depends on the background illumination. With electric light, that may even change from one shot to another.

I would set the camera to manual mode, then adjust the time and aperture until you get a neutral exposure of the background (with the flash off). You can experiment with that before you take the actual shot, since the background will be there even if the band is not.
Now if you don't like the ISO you get here, or the time is too long (or both), you have to adjust these until you are satisfied. You can take a test picture of the background with that setting too, to see what it look like.

After that, if the only flash you have is the on-board one, then look in the table and see how far off you can be. Remember that the guidelines are normally written with the condition that you should be indoors, where you have a white ceiling which will help reflect some of the light forward to your subject. You'll not have that help, so your range will be shorter.

Thanks Anders. If I understand correctly, expose for the background ambient and add flash. And theoretically, the foreground will not be over/under exposed by the flash. Correct?

There is a common misbelief that there is Flash as fill mode versus Flash as main light mode...but it is untrue. the camera has only one single output strength for flash -- regardless of fill versus main light function... The Flash intensity is identical for P or M or AV or TV

Yes, it's not the flash that makes the distinction. It's how you expose the ambient.
In this case I'd let the background be a tad low key, - 1/3 or a little more. That would give you leeway to add a little flash light without overexposing the main subject.

I had HUGE problems with the 70D and BOUNCING a hot-shoe flash. I had no problems with the pop-up flash.

The 70D (nor any other Canon camera) does not AUTOMATICALLY set ISO 400 with flash. They set ISO 400 IF YOU SELELCT AUTO-ISO. If you dial in ISO 640 or 12800, it will honor that setting, if it is working properly.

I would avoid YN flash units. I've had 2, one new and one used. Neither worked properly. Some 430EX II units are selling (used) for less than $100. I recently picked up 2 550EX units for $45 each. I've seen 580EX (not II) units for less than $100. 580EX II units are available for just over $100. I've always had really good luck with Canon Speed Lites.

That said, I do use YN-622 & TX for controlling my Canon flash units. Wonderful little doodads.

Thanks Tom. Yes, I meant the ISO foes to 400 automatically when ISO is set to auto. Thx for the tips on speedlites.

If you set AUTO-ISO while in (P)rogram mode, I believe the camera will select ISO values up to 1600 when needed. The proper way to shoot flash, IMHO, is (M)anual mode. Control ambient with shutter speed, and let ETTL take care of you subject/flash exposure.