View Full Version : focus and exposure
02-25-2012, 02:09 AM
had a question about focus and exposure?
If the camera is on the pole. How would I know what the optimum focus and exposure to set?
Can't rely on AF.
Even though its a fisheye with a good amount of DOF, I generally always try to work towards setting the Hyperfocal distance.
How would I set exposure and focus without seeing through the camera ?
02-25-2012, 07:06 AM
You mentioned " I generally always try to work towards setting the Hyperfocal distance." You are the only one who knows your lens and camera settings. Different fisheye lenses and cameras require different settings.
Hyperfocal distance and exposure would need to be set thereby assuring maximum depth of field before using it on a pole.
We use a Sigma 8mm full circle lens on a Canon 5d and Canon 500d (T1i).... Canon 5d full 35mm sensor is HF .9 feet and Canon 500d NON 35mm sensor is HF 1.4 feet markings on the lens. There are NO specific lens markings for these postions on the Sigma 8mm fisheye lens. So trial and error technique is the only way we can locate the HF points. IF your camera has LIVE VIEW.. that helps with focusing.
02-25-2012, 10:38 AM
Canon 5d full 35mm sensor is HF .9 feet and Canon 500d NON 35mm sensor is HF 1.4 feet markings on the lens.
The figures don't mean much without the aperture setting.
02-25-2012, 02:48 PM
The point I'm trying to make is,
How do you control exposure and focus with the wireless remote?
Unless you tether it or get the fancy Hahnnel live view remotes.
How is everybody working these key things?
Its a given that focus and exposure from any given height will change.
Settting it prior to raising the pole will have a different result.
02-25-2012, 10:20 PM
in theory you are right. Most of us use the "Hyperfocal Distance". Which even often is taped on the lens rings. Please, no discussion about this...:th_wink:
To be sure about focus you should do test shots for the apertures you use focussing around the HF from 1.5 to 0.5 for example if HF is 1m. Then choose the sharpest setting as your "HF". Before you raise the pole preset to this value.
A nice APP : http://itunes.apple.com/de/app/lens-lab/id452548360?mt=12 In case you like to focus to something different which is more interesting in front or behind the sharpest HF point you can check this easily with this APP to get an imagination.
Exposure: I set my camera to A Mode and watch the shutter speed moving around from click stop to click stop or just from lightest and darkest point. Then I decide for the shutter speed. You can bracket around your decision, just shoot +2EV -2EV, or shoot RAW, +/-EV and do the rest afterwards in the software.
You can also check the histogram of your exposure test shots or use live view with any Hahnel like wireless remote. So there are many way's to Rome. To get to know about the theoretically differences between exposure on the raised pole and on the ground you could make test shots. Set camera to A Mode, take shots on the ground and on the raised pole and you can check the shutter speeds.
Would be nice if you tell us about them.
May be you got some answers to your questions.
02-26-2012, 08:38 AM
John, you are very correct. Most of the time f-stop/8 using Canon 500d Sigma 8 with HF 1.4. good sharp imaging.
Canon 5D, Sigma 8 fisheye, with HF .9 which is at the Sigma 8 at HF 11 mark
I did try moving the center mark "o-|-o" on infinity mark around to the Sigma 8mm fisheye hyperfocal mark f/11.
Set the camera to a/v priority then tired for greatest dof using f 5.6, 7.1, 11, 16, 22.
Made one raw image at each f/stop.
Then brought all images into Adobe camera raw and corrected for Chromatic Abberation.
then in Photoshop at 100% zoom in examined all for sharpest image.
f-22 image was visually sharpest.
Not looking for what is in focus at 1 meter.
Would like to get ALL in focus from 11 (12" x .9 = 10.8 ) inches in front of the film plane mark on the camera to infinity.
With a 5d [no live view] it is not practical for us to try viewfinder sharpest focus we can get focus sharp but not tack sharp.
this is why we are trying to let the camera get the tack sharp and greatest DOF using hyperfocal technique.
We are using the NN R1 and have it calibrated properly for NPP.
PTgui 9.1.3 stitching is repeatable sucess with values less than 1 (like .9 or .6").
So RAW and 16 bit tack sharp TIF's and "all" in focus is our goal.
For what it is worth, the Canon 5d custom functions cfn when enabled permits ISO to be set to 50 or 'L' for lowest film grain or noise.
So we have our ISO set at 50
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