Auto Focusing Issue in a Dark Studio

Hi. I just setup a very small home studio and having trouble with my auto focus. I have one AB400 with a 30x60 softbox and have set the power to 1/32 in order to shoot wide open on my 5DII 50mm 1.4. With my ss at 200 and ISO at 100, I meter at 1.6.

My "studio" is actually our baby's bedroom and I have been shooting at night so there is no ambient light coming in the windows. I have one overhead bedroom light but I leave that off because it throws off my wb. I just use the modeling light from my AB400 on at all times. However, since I keep the power to 1/32, the modeling light is very, very low. I keep my 5DII on the center AF point - a must in low light - but I still cannot get a focus lock on my subject.

I came up with an idea to have my assistant (aka the wife) shine a flashlight close to our baby's face in order to have enough light for the 5DII to get locked. Once I'm locked, she turns the flashlight off and I take the photo. The results are great but there has to be an easier way.

Any suggestions from you studio experts out there? I can't believe that this is my only option!

Why don't you try turning on ISO expansion and shoot at 50 ISO? That will get you another stop of modeling light power to play with?

MDEphoto wrote in post #14481834
Hi. I just setup a very small home studio and having trouble with my auto focus. I have one AB400 with a 30x60 softbox and have set the power to 1/32 in order to shoot wide open on my 5DII 50mm 1.4. With my ss at 200 and ISO at 100, I meter at 1.6.

My "studio" is actually our baby's bedroom and I have been shooting at night so there is no ambient light coming in the windows. I have one overhead bedroom light but I leave that off because it throws off my wb. I just use the modeling light from my AB400 on at all times. However, since I keep the power to 1/32, the modeling light is very, very low. I keep my 5DII on the center AF point - a must in low light - but I still cannot get a focus lock on my subject.

I came up with an idea to have my assistant (aka the wife) shine a flashlight close to our baby's face in order to have enough light for the 5DII to get locked. Once I'm locked, she turns the flashlight off and I take the photo. The results are great but there has to be an easier way.

Any suggestions from you studio experts out there? I can't believe that this is my only option!

I'm not sure how the AB's work, but it sounds like your modelling light is proportional to the output power, is there a way to separate the two?

I know elinchrom has this function, I would be surprised if the AB's didn't have something similar.

just looked at the AB400
from site
"The modeling lamp can be set to full brightness, turned completely off, or set to track the power changes."
http://www.paulcbuff.c​om/b400.php

set the modelling lamp to full brightness so you have enough light to focus with?

from the manual
"The modeling lamp can be set to full brightness, turned completely off, or set to track the power changes by pushing in the grey TRACK button."

I think part of his issue was the modelling light was causing WB problems otherwise i would just say use the modelling light at full power.

Turn the modeling lamp on full and not track.

When I shoot remote with a VLM in the dark sometimes I will use a flashlight to shrink pupils and gain focus (with my old 5Dc).

ABs at 1/32 power. Just shoot with modelling light alone.

At ISO 100 and 1/200 at f1.4 you should be able to keep a light on in the room as the flash should over power the ambient anyways. I was actually shooting at ISO 100 1/200 at f1.8 on my 5DII 85 f1.8 last night and with a track lights on and lamp on, I completely eliminated the ambient just fine.

Kechar wrote in post #14484257
Turn the modeling lamp on full and not track.

This alone will give you 32 times (5 stops) more light, theoretically.

Also, use a more powerful modeling bulb. I use 250w halogens in my Alienbees.

Thanks to all for your help! Obviously I can't read and missed the fact that I had the track button on. I turned it off and now the modeling light is on full power. I will say that on full power it might be a little too bright for newborn photos but much better than having someone hold a stupid flashlight!

And Bobby, 1/32 is perfect it you want the shallow dof that you can't get with powering up at 1/16 or 1/8. If there is another way, please let me know.

Best Regards to everyone!

Only reason I mention 1/32 is that your pop to pop power variations and WB variations are going to be too much. I rather use higher power like 1/4 with ND filter on the lens or strobe to shoot wider apertures.

If you are shooting at 1/32 why not just use your 430 ex II with af assist beam on?

Brendo666 wrote in post #14485662
If you are shooting at 1/32 why not just use your 430 ex II with af assist beam on?

Probably because he wants to use the softbox.....

Throw an ND filter on the lens and bump them lights on up!

Brendo666 wrote in post #14485662
If you are shooting at 1/32 why not just use your 430 ex II with af assist beam on?

I tried with the 430 EX but could never get the results I can get with the 60x30 softbox. I am a newbie with lighting and found a great baby photographer who shared their lighting setup and essentially copied their setup. I use small fabric backdrops and don't like going smaller than 2.8. So far I have been extremely happy with the results with the setup and the AB400 with the giant softbox.