Question on zooming with shutter open

Richard

I am having problems getting the focus correct in a somewhat tricky shot I am attempting. I want the expanding, radial blur that you get when you change the zoom with the shutter open, but I want the center to be fairly sharp. Here's what I have tried so far: Focus manually on the subject with the lens set to around 50 mm. Then start a 3 or 4 second exposure at 75 mm and slowly zoom to 50. I am using a flash on 2nd curtain synch, and a tripod. I have the camera about a meter from the subject. I suppose the problem is that I am not getting my final zoom length exactly at the point I used to do the initial focus.

Any suggestions?

Thanks.

jdryan3

Richard -
I have had to do this by using a fairly long exposureso you need to use a tripod. Then do the zoom in/out at the end of the exposure. So on a 20 second exposure, you zoom at 16-17 second, dragging out the zooming slowly for 2-3 seconds. Obviously you could do 10 seconds and quickly zoom at the last second.

Another option is one shot normally exposed and another zoomed. Use PS to layer/mask the images, feather and blend to your taste. I'll try and post an example later of the first method.

Richard

Dave,

Thanks for the suggestions. I think the one that's going to help the most is to start zoomed out, then zoom in. That way, I can focus exactly on the part that I want sharpest. I was doing the opposite. :bash

BTW, I looked at some of your galleries. Your Madrid is a little different than mine. Nice work.

Cheers,

Antonio Correia

Richard. Good evenning.:D

I have done a zoomed photo on the 7 th July with good results.
I have shot some 5 pictures hoping 1 to be good.
It's here.
I think an important procedure is to zoom smoothly and rotate the ring without touching the lens or the camera.

I didn't care about the focus, but, as you are shooting very bear and I was to infinity, I suggest you do as you told us.

Richard

Antonio Correia wrote:

Richard. Good evenning.:D

I have done a zoomed photo on the 7 th July with good results.
I have shot some 5 pictures hoping 1 to be good.
It's here.
I think an important procedure is to zoom smoothly and rotate the ring without touching the lens or the camera.

I didn't care about the focus, but, as you are shooting very bear and I was to infinity, I suggest you do as you told us.

Hi Toni,

That's a very cool shot you did. I finally got something close to what I was aiming for using a tripod, first curtain flash and zooming in rather than out. I posted it on Dgrin a few days ago. Final version here.

Salud,

Antonio Correia

But that is very nice Richard !
Come on, you do know how to do it !!!

Richard

Antonio Correia wrote:

But that is very nice Richard !
Come on, you do know how to do it !!!

Now I do, but I'm not going to tell you how many tries it took.

Antonio Correia

rsinmadrid wrote:

Now I do, but I'm not going to tell you how many tries it took.

No. You will not.
But I'm sure you tried over and over.
Everybody does. Digital advantage !

SloYerRoll

rsinmadrid wrote:

I want the expanding, radial blur that you get when you change the zoom with the shutter open, but I want the center to be fairly sharp.

You could always put a snoot on a speedlight set to rear curtan sync & get your slow zooming exposure. You can even hald hold the entire exposure and get some neat effects w/ the subject still sharp.Whatever the flash hits will be in perfect focus with all the blur lines you like from the abmient exposure. {The exposure will be fine even w/ the flash close, since the high aperture offsets the intensity of the strobe}
You could even hand hold the exposure for some neat effects and still keeping your focal point sharp.

Just remember that aperture controlls speedlights/strobes and shutter speed controlls ambient.

Jon

Richard

SloYerRoll wrote:

You could always put a snoot on a speedlight set to rear curtan sync & get your slow zooming exposure. You can even hald hold the entire exposure and get some neat effects w/ the subject still sharp.Whatever the flash hits will be in perfect focus with all the blur lines you like from the abmient exposure. {The exposure will be fine even w/ the flash close, since the high aperture offsets the intensity of the strobe}
You could even hand hold the exposure for some neat effects and still keeping your focal point sharp.

Just remember that aperture controlls speedlights/strobes and shutter speed controlls ambient.
Jon

I'm not sure I understand this, Jon. I would think a snoot would keep the flash illumination constrained to the center, but doesn't the focus depend on the focal length and lens focus setting? I think in autofocus mode, the focus setting is determined when you click the shutter, but the focal length will have changed by the time the flash goes off in 2nd curtain mode.

SloYerRoll

rsinmadrid wrote:

I'm not sure I understand this, Jon. I would think a snoot would keep the flash illumination constrained to the center, but doesn't the focus depend on the focal length and lens focus setting? I think in autofocus mode, the focus setting is determined when you click the shutter, but the focal length will have changed by the time the flash goes off in 2nd curtain mode.

Yes the focus depends on the focal length and focal point you use. But you can tell your camera what you want to see when you click on the shutter.
How I envision the shot you mentioned is a focal point on one thing so a strobe and snoot would be how I would approach this.What I picture in my mind and what you picture are quite possible two completely different things though.

You definately want to lock in on your final focal point w/ AF then switch to MF so your focal point doesnt change for this shot. I'd also shoot this on a tripod so focal length will be easy to determine.

Here's how I would approach this:

• Manually set the strobe to a high power selection (1/2 - 3/4)
• Get the strobe physically very close to the focal point.
• take a few test shots and adjust exposure by increasing aperture to taste (the fstop numbers are going to be very high). If you are still blowing out the shot at the highest ftop, just adjust power down on the strobe accordingly. Don't back up the flash to adjust light if possible. This helps keepthe hard light out. (how it does that video)

This high aperture gives you a great dof and that gives you a sharp picture w/ room for play so being dead on isn't that much of an issue if there is any play.

If you need more dof, just back out the focal point a bit and try again. I just found out from LiquidAir that focal point affects dof as well. post #7 on this thread

I'll do some test shots for you in about two weeks if you like. I'm about to move my family to Bend, OR this week and things will be boxed up for a little while.