Another Great Feature from Leaf Capture 11.5: Lens Calibration when Shooting to CF Card
Yair Shahar, Leaf Product Manager, shares his experiences with Lens Calibration when shooting to CF card - a new feature for Leaf Aptus-II models available via Leaf Capture 11.5.
Those who use their digital backs (Leaf or others) are mostly familiar with terms such as “Lens Calibration”, “Color Cast”, “LCC” etc. These all relate to the same basic “effect” caused by using a wide angle lens that sits very close to the sensor. In reality this means that your images will often show non-uniform Magenta, Green, Cyan and Yellow color cast across the frame, something that looks like this:
The above image also shows some luminance falloff, caused by shifting the lens (or the back) and getting near the edge of the lens’s image circle.
Until now, you would have to pull out your White plastic diffuser filter, adjust the shutter speed (to allow for another 2 stops of light to come through), take another shot and then later use your choice of software (in my case Leaf Capture or Capture One) to correct for these casts and fall off effects.
Well, now we enter a new era…let me start from the end:
You will notice that the casts are gone as well as the fall-off/ vignetting and that the image looks a lot cleaner in terms of color and tonality. The news is that this is how it came off the CF card!!! I did some minor adjustments in Capture One for exposure and saturation but I skipped the LCC process altogether!
So How Does it Work?
Shooting tethered to my laptop while mounting my camera on a mini-tripod (12”), I created two sets of calibration shots for f8 and at 5mm rise increments, one set for vertical frames and one for horizontal frames. So a set would look like:
* Focal Length _ Aperture _H/V _ rise (in mm)
In Leaf Capture 11.5, there’s a new menu item called Lens Calibration>Save for CF card. This takes the calibration shots and converts them into data files that the back can read and can use on-the-fly to correct for color casts and luminance falloff.
After that, these files are stored in a designated folder on the CF card(s). With a bit of practice this process becomes very easy and in the field, all you have to do is to select a Calibration file before taking a shot at e.g. f/8 and 10mm rise and Bob’s your uncle! Of course you can make as many files as you need or like to cover almost any aperture and lens displacement combination. This may take longer although many of the photographers I work with would appreciate a limited choice as it speeds up their work. Leaf has also built some level of tolerance into the algorithm so a change of 1mm or a 1/3rd of a stop won’t affect the result too much.
While making them you can also set the amount of fall off correction; personally I like to keep some vignette especially when there’s a lot of sky in the photo.
The new Graphic User Interface which comes as a part of the new Leaf Capture 11.5 helps to make it a lot easier now to navigate through the menus and the “Outdoor” color theme makes it easier to see the LCD outside.
The beauty in this new feature is twofold:
I would recommend this new software to anyone who uses a technical camera, especially with wide-angle lenses. All you need to do is to download the new software, install it on your Mac and then connect your back and let it upload it.
I would even go as far as suggesting a new Leaf Aptus-II back! It is THAT good!!!
If you are facing any issues please contact our support team: http://www.phaseone.com/en/SupportMain.aspx