Question about focusing with the Sony 50mm/1.4...

[WhyBe]

I was shooting a model with this lens and noticed that when I did full body shots, the face was not in focus.

What I do:
Sony alpha a350 - RAW
Two Alien Bees B800
White Background lit with B400
Optical Trigger
Spot Metering
Spot Focus
Auto Focusing - (AF-S mode)
ISO100
Shutter 1/60
Aperture F2

I stand back far enough to capture the entire body of the model (5'7")--no farther than that.
I place the spot focus on the face then half-shutter to lock-in focus.
While holding half-shutter, I bring the entire body into the frame (still half-shutter, standing in the same spot)

On the camera viewfinder, the pictures look great. But once I view them in LR2, the face is not a sharp as in my portrait shots. In fact, nothing is. I am not a pro, so I may be facing a simple problem that you all may have figured and solved years ago

Am I outside of the maximum focusing distance of this lens (If there is such a thing)?

[David Kilpatrick]

When you do centre focus and recompose, it does not work at f/2. The focus plane is say 2m from the subject at the centre, but 2.1m (or whatever) at the top and bottom of the frame (draw a triangle and you will see why). Your subject is probably not dead parallel to the camera, at eye level you need to angle it down. f2 is an extremely wide aperture and you won't get face and body in focus at the same time with the camera angled down.

Try shooting full length pictures from a waist-level tripod height. It is more flattering usually. Also, your camera will be parallel to the subject and focusing on their body should ensure the face is also sharp.

And try apertures like f/4 or f/5.6, they will look like the viewfinder image - f/2 will not.

David

[jcoffin]

Most modern viewfinders don't diffuse the light very much (that's a large part of why they're so much brighter than on older camera), which means they don't show depth of field very accurately -- by the time something is far enough out of focus to look slightly blurred in the viewfinder, in the real picture it will be a great deal more blurred, often to the point that it's nearly unrecognizable.

As for how you're doing your shooting, my advice would be to focus on the eyes like you're doing now, but then instead of pointing the camera downward to get a full-length shot, crouch down so the camera is around waist level to shoot, and keep the camera pointing straight forward. That will usually keep your focus quite close to where it was to start with.

[WhyBe]

OK guys, thanks for the advice. Actually, I should have said I primarily shoot on my knees, so most of my shots are already waist level. The F2 aperture being too wide makes sense. I will try narrower apertures until I get everything I need focused (didn't realize DOF was THAT narrow for F2). I will probably compensate by increasing ISO. And now I realize that I can't soley rely on the viewfinder to check quality.

I also noticed another problem I was having. I was viewing the pics on my 12" (1024 x 768) screen Laptop. Viewing the same pics on my 17" (1280 x 1024) laptop made them look more like what I was expecting . So I was seeing a combination of narrow DOF (from the F2 aperture) and scaling distortion in LR2.

I 've learned alot today. Thanks again.

[David Kilpatrick]

The Alien Bee B800 and B400 heads - are these flash? I'm slightly confused because I thought these units were 800Ws and 400Ws monobloc flash heads. With that level of power in a studio, you can shoot at f/16 for a full length at ISO 100, even if you are using 1.5m octas or 44 inch white brollies - or whatever. There's so much power there that getting to f/2 usually means using an ND filter on the camera even at minimum flash level.

I normally work with two 600Ws heads and a typical full length set-up would end up around f/11, ISO 100.

David

[WhyBe]

OK, David, I guess I still have a lot to learn then
I have the 60" softbox on one and a 40" umbrella on the other (if I'm remembering those sizes correctly). Typically the B800 with the softbox is at full power and the one with the umbrella is usually half the other or less. The umbrella is off to the side 90 degrees or less. I run the B400 on the background at full power, sometimes through a color gel with a black background. I'm wondering is it: the size of my softbox or my placement of it is forcing me to use it at such a high power? It is placed 45 deg as close as I can get it to the subject without being in view.

[David Kilpatrick]

If you honestly are at f/2 with that setup, I don't think your flash is firing in sync. Are you triggering the AlienBees with the built-in flash? That does not work, they fire before the exposure and all you get is modelling light plus a hint of flash afterglow. Are you triggering with a cord sync and flash adaptor? That should work. So should a flash adaptor with a radio or infra-red sync trigger.

I suggest you borrow a flash meter, and trigger the AlienBee setup with that, and make a reading. There's no way with any of my flash - even the stuff which goes down to 1/32nd power - that a decent normal lighting set up would need f/2.

David

[WhyBe]

Wow, David, I guess that explains why I'm at F2. I've been screwing up all along
Yes I am optical triggering with the built-in flash. I haven't went to any other means of syncing. Soon as I'm able, in may go the Pocket Wizard route or try the new White Lightning sync system. In the meantime, what if I triggered the Bee's using my HVL-F56 set to a low power? Or would that exhibit the same synce problem as the built-in flash?

What's weird was when I purchased the lights, I asked the salesman how could everything stay perfectly in sync when triggering optically and I'm moving things around...he said they just would...

[David Kilpatrick]

The HVL-56 can be set to minimum power, and the camera should be set to manual 1/160th shutter speed, aperture - I suggest you try the AlienBees at 1/4 power and try f8 at ISO 100 as a start point with your setup. If you want to use Live View, you must set Aperture Priority (A). This will auto-set the flash sync speed probably to 1/60th, but it will let you use any aperture you need, and give you a proper brightness of live view. Manual will not.

Unfortunately you can not use Live View with a PocketWizard or any other trigger. No adaptor exists which enables the auto gain by simulating the flash-ready signal of the F56AM or similar gun.

Remember, your studio kit will trigger with the HVL-F56AM aimed upwards. It does not need to aim at the subject. In fact, it's probably the best way of triggering studio flash with the A350.

David

[WhyBe]

I don't use live view at all and I bought the a350 because of it . I had the F828 before that and was spoiled by it's better live view functionality (assuming I would get the same in the a350). But now, I only use the viewfinder and shoot in manual on the a350.

When you say "flash sync speed", is that used interchangibly with "shutter speed"? Otherwise, I don't know what parameter I would set to adjust sync speed. And what would allow the HVL-56 to sync better with the Bee's than the built-in flash?

[David Kilpatrick]

Yes, flash sync speed just means shutter speed. The flash sync shutter speed range is 1/60-1/160th on auto, with studio strobe the faster speed is best as it reduced the effect of modelling light on the colour.

The HVL-F56AM in manual mode only emits a single flash, which means it can sync the studio kit. The built-in flash has no manual mode, and always works with a pre-flash whether ADI or TTL pre-flash mode. This trigger the studio heads before the exposure happens, it is just a measuring flash burst, but the AlienBees do not know that.

I use Elinchrom BXri heads which can 'learn' the pre-flash sequence of built in flash, so I can use the A350 pop-up as a trigger if I want. AlienBees can not learn the pattern, but they are much cheaper.

David

[WhyBe]

OK, thanks David. Lot's of great info here. I'll start triggering with the HVL until I get some radio triggers.