Focusing problem with flash

[eirefoto]

Friends, I have a problem combining autofocus and on-camera flash. To some of you, this will sound simple but I have never tried any other setting apart from ETTL on my Canon 580EX II. I use a 5D III and a 7D but the problem is the same and this is it:

In a group shot (e.g. three rows of people, maybe 7 in each row) only the front row is in focus (obviously I choose a face in the front row for my focus point). The second and third rows are quite a bit out of focus. I could of course choose a face in the second row but . . .

Rather than setting everything on Auto, how can I get a deeper depth of field in my group shots - in other words, what settings should I use so that all three rows will be sharp?

I know it sounds basic but I'm afraid I just don't know. I find the 580EX II manual confusing. I would appreciate any help. Thanks.

 

[Ellis Vener]

Focus in the middle row and work at a smaller aperture like f/11 or f/16. That may require you to work at a higher ISO to avoid underexposure.

 

[eirefoto]

Thank you. I thought that might work but it's the smaller aperture that gets me. If I set a smaller aperture say in AF or MANUAL mode, will the flash automatically compensate for the lack of light? I tried this last night but results were totally dark. Should I change from ETTL mode on the flash?

 

[fotowbert]

Thank you. I thought that might work but it's the smaller aperture that gets me. If I set a smaller aperture say in AF or MANUAL mode, will the flash automatically compensate for the lack of light? I tried this last night but results were totally dark. Should I change from ETTL mode on the flash?

Adding to what Ellis said about increasing your DOF (Depth of Field). Set the camera to Manual or Aperture Priority exposure mode so you can specify (force) a smaller aperture like f/11.

Leave the flash in eTTL mode so it will output the correct amount of light. By using a higher ISO your flash won't have to work as hard or perhaps run out of light if you are bouncing in a large venue.

This technique done correctly doesn't result in a totally dark image.

• John

 

[Ellis Vener]

Thank you. I thought that might work but it's the smaller aperture that gets me. If I set a smaller aperture say in AF or MANUAL mode,

I think you mean Aperture priority (A) and not the Autofocus (AF) mode.

will the flash automatically compensate for the lack of light?

Up to the limits of how much light it is capable of emitting.

I tried this last night but results were totally dark. Should I change from ETTL mode on the flash?

No you should not but you should test again as you may be reaching the limits of your small flash's capabilities. If that is the case then you should manually set the ISO (sensitivity amplification) and adjust the ISO setting upwards until you think the images are properly exposed.

Also keep in mind that if you are using any kind of diffuser, it is just about assured that you are knocking down the light by at least a stop if not more, or if the light is pointed anywhere but straight at the subjects, that will serious compromise your maximum range.

--
Ellis Vener
http://www.ellisvener.com
Most photography is not rocket science, just snapshot keepsakes. But when when it does get technical it helps to think like an engineer. The fun is found in just being there, not minding equipment.

 

[eirefoto]

Thanks John. I will try that out.

 

[eirefoto]

I meant AV, sorry.

 

[eirefoto]

Very helpful, thanks. I normally do use a diffuser but not last night. I was bouncing though. It's more the sharpness than the brightness I'm worried about. Even if the shot is brightly lit, the back rows are out of focus.

 

[fotowbert]

Very helpful, thanks. I normally do use a diffuser but not last night. I was bouncing though. It's more the sharpness than the brightness I'm worried about. Even if the shot is brightly lit, the back rows are out of focus.

Posting a sample image with EXIF intact would help us understand your issue.

• John

 

[eirefoto]

Very helpful, thanks. I normally do use a diffuser but not last night. I was bouncing though. It's more the sharpness than the brightness I'm worried about. Even if the shot is brightly lit, the back rows are out of focus.

Posting a sample image with EXIF intact would help us understand your issue.

• John

--
It IS switched on!

 

[fotowbert]

Very helpful, thanks. I normally do use a diffuser but not last night. I was bouncing though. It's more the sharpness than the brightness I'm worried about. Even if the shot is brightly lit, the back rows are out of focus.

Posting a sample image with EXIF intact would help us understand your issue.

• John

--
It IS switched on!

Thanks for posting the image. I can see why you are disappointed in it. IMO there may be something besides shallow depth of field going on here because the front row doesn't appear much sharper than the back row. Even wide open at f/4 I would have expected the front row to have been better since you say that is where you focused.

Ambient light accounts of a portion of the total exposure because the flash shadows aren't totally black. When there is ambient light content there is the potential for camera motion to blur the image somewhat but you have IS active. If the camera was on a tripod IS should be turned off unless your lens automatically detects tripod use.

I would make some test shots eliminating potential sources of blur/error until I got tack sharp results. Hopefully you will uncover what is responsible. If you describe in detail how you took this shot something might be obvious.

• John

 

[eirefoto]

Thanks John. I hand-held the camera in a room with a high ceiling. I took five group photos and not one of them is sharp. I wonder if it would have anything to do with lens calibration?

 

[Sailor Blue]

There are reports that the Canon 24-105mm f/4 results are disappointing at 24mm, and being wide open is never good for sharpness, so that could be part of the problem. Just closing down to one stop will dramatically increase the sharpness for most lenses.

Checking to find out whether or not you need Auto Focus Microadjustment is something you should do with all lenses. With the 5D & 7D (don't know about the 5D III) you can only have a AFM at a single focal length so with a zoom lens you need to test at the shortest, medium, and longest focal lengths and use a median value.

Dot-Tune: Autofocus Fine Tuning in under 5 minutes - FM Forums

Even in a room with a high ceiling I would focus on the middle row and bounce my flash head at the ceiling just in front of me to give me even lighting. With my Canon 7D I would use Manual mode with a shutter speed of 1/160 sec, f/5.6 with the 24mm-105mm f/4 lens, Auto ISO, and E-TTL. A test shot would tell me how much to adjust the Flash Exposure Compensation.

I would expect to see an ISO of 800 or higher so noise is going to be present in the image.

 

[eirefoto]

That's very helpful. I also have a 16-35 f4 L which would probably be better to use in situations such as this. I'll try it.

 

[Knoxis]

I'm a bit confused by what you are saying, but ultimately what I can offer you is that to get a deeper depth of field, you need to use a smaller aperture, or a high F-stop number (i.e. F8, F11, etc...). Changing your flashes settings will not alter the depth of field at all. Since you are already on ETTL, you can simply stop down the lens from its maximum aperture and the camera will set the correct flash exposure.

 

[eirefoto]

I am very much aware that a smaller aperture will give me a deeper depth of field! If you read my problem carefully, you will see that I'm not getting enough light when I set a small aperture!

 

[john isaacs]

I am very much aware that a smaller aperture will give me a deeper depth of field! If you read my problem carefully, you will see that I'm not getting enough light when I set a small aperture!

If you used a DOF calculator, you would see that you have plenty of DOF with a 24mm lens at f/4 at a distance of what, 15-20 feet? It's not likely to be your focus calibration, either, but you can always check by taking a shot with manual focus (use live view and magnify).

I don't see anything in sharp focus in the shot. Could be the lens; take a shot in better light and lower ISO but f/4, and see if it gives sharp results. With high shutter speed...you might not be holding stable at 1/60. And take some shots stopped down; that should sharpen up the images.

If you need to stop the lens down for sharpness, then you need to add more light. Get a second flash and try that.

 

[Ellis Vener]

I am very much aware that a smaller aperture will give me a deeper depth of field! If you read my problem carefully, you will see that I'm not getting enough light when I set a small aperture!

Then you need either more light -,either a more powerful flash or a second one, or get rid of any softbox or diffuser or don't bounce your light - a higher ISO setting on the camera, or both.

Are you sure that neither the camera or the flash were set to a negative exposure or FEC value?


Ellis Vener

http://www.ellisvener.com

Most photography is not rocket science, just snapshot keepsakes. The fun is found in just being there, not minding equipment.

 

[LordKOTL]

I am very much aware that a smaller aperture will give me a deeper depth of field! If you read my problem carefully, you will see that I'm not getting enough light when I set a small aperture!

Ya know, I may be completely guano here, but it looks like your EXIF file previously in the thread has a bit of vignetting. It's almost as if your flash is just not powerful enough or dispersed enough for a wide-angle lens.

I had a similar problem very early in my photography journey shooting a miniscule SB-30 with a 28mm lens in a cave back in my film days. The flash wouldn't "throw" and the edges were darker than the center.

I'm not too familiar with Canon's line, but using ETTL, can you compensate--like set the flash at +1 or +2 to see if that makes a difference? I believe if you bounce or diffuse the camera won't automatically compensate for the reduction of flash power--I could be wrong there though. It could also be (as mentioned) that the flash itself is at it's limits and you need something more powerful. It might be that the distance to/from the ceiling is really pushing the ability of the flash.

I think checking your AF calibration is a good idea as well, as well as stopping down to see if that helps sharpness, but I also think you need a bit more power in the flash, or your flash isn't powerful enough.

My $.02

 

[BAK]

You write: > (obviously I choose a face in the front row for my focus point).<

I think by now you've read answers that explain you need to focus about 1/3 of the way into the important part of the shot, not on the first row.

The range of the depth of field (more in a minute) places about 1/3 of the sharp zone in front of where you focus, and 2/3 behind the focus point.

Use manual focus to make sure the lens does not refocus somewhere you do not want.

Depth of field increase as the aperture gets smaller, and visa versa. You know this.

You note your later test shot with a small aperture was black. What was your smaller aperture? Did you overdo it?

F11, in the same circumstances as your demo photo, should have at least let you see the picture, even though it might be too dark to use.

Your shutter speed is too slow.

Set your camera to manual exposure, 1/125th of a second, f8 for a big "deep" group like that.

For a good exposure of the subject at f8, you need less than about 15 feet from flash gun to ceiling and down to the subject, at ISO 400

Yes, the Canon 580EX instruction book is confusing if you don't already understand flash, and flash-math.

I do not think your camera is broken.

Just set things manually, and test.

BAK