Luminous Landscape Forum
Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: Alun on June 14, 2012, 01:30:08 pm
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I wonder if anyone can assist me?
I have just picked up a Leaf Aptus II 7 back. It has 12 stops of dynamic range but I wondered if anyone accurately knew how this was distributed? Normally it's more stops to the shadows than the highlights but id like to set my light meter up to reflect this
Thanks in advance
Alun
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Does it really work to use light meters that way with digital sensors? What 18% gray becomes in the final picture would depend on the contrast curve in post-processing, which could be different depending on how contrasty the overall image is, this means 18% gray in the final image is not always represented by the same sensor raw values.
The "usual" way to do it digitally is to know when the sensor clips and put your highlights just below (ETTR).
Also note that the stops close to black are so noisy one could hardly call them usable, so the actual number of "useful" stops is closer to ~9.
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The scene dictates the DR, the back can capture UP TO 12 stops
If you look at the histogram in Leaf Capture it'll tell you how many stops the back is "seeing" for a specific scene
Here's an image of a scene that covers about 10-11 useable stops, shot with an Aptus-II 7. You can lift the shadows as much as you like without any noise showing...
It is about 1/2 a stop over exposed
Enjoy your new camera!
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Many thanks Torger and Yaya for the quick replies. Maybe I should explain a little more how I was planning on using my meter. I would take the reading of the brightest spot in the scene and then place that at the limit of the sensor on the light meters scale and work that back to which exposure I would need to achieve that.
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You can use the spot meter on the back's histogram, which will tell you the exact exposure of your highlights, in numbers and also with a line. You can then take a reading with your light meter of that same area and "calibrate" it so you'll know when it shows you the correct exposure
If you shoot tethered into Leaf Capture you can use the picker tool which is similar to the spot meter. In Capture One it works a bit different but achieve the same results
hope this helps
yair
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Yes it does - thank you!
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It has 12 stops of dynamic range but I wondered if anyone accurately knew how this was distributed? Normally it's more stops to the shadows than the highlights
Basically, there is roughly 3 stops of DR above the metered 18% mid-tone. That would imply roughly 8 stops below it. The lowest few stops will be terribly noisy.
But the 18% grey card/light meter thing is only a guide in MFD, since it depends on how faithfully the manufacturers adhere to the saturation definition of base ISO (they tend to "overdeclare" it, which gives more highlights headroom than you'd expect; perhaps because they think that this is what photographers want; that or the faster shutter speeds indicated by a higher ISO). And since a source of illumination, or a scene area under stronger illumination than your surroundings, can saturate (and even worse, bloom into adjacent pixels in the same column), even when you meter everything else in the scene on the basis of its reflectivity or use a reflective grey card, you are not guaranteed success with that type of metering. As Torger and Yair suggest, doing it by the histogram is a better way to maximise signal to noise without either saturating or underexposing unnecessarily.
Ray
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Many thanks for the detailed reply Ray. It would seem that I have a learning curve to shoot medium format digital!
On a separate note, does anyone have a cheap recommendation for a plastic cover if I were to temporarily leave the adapter plate attached to the back? I suppose like most everyone's, the adapter plate is 110mm x 110mm.
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On a separate note, does anyone have a cheap recommendation for a plastic cover if I were to temporarily leave the adapter plate attached to the back?
It's not a proper answer to your question but this is what I do: The only such cap I know of is the Alpa one and this isn't as dust proof as the back's original metal cover plate. So I decided to leave the adapter plate on the camera body and use a cheap Mamiya cover for the adapter plate (http://www.mamiyawebshop.nl/mamiya-accessoires/mamiya-645afd-serie/body-lensdoppen.html).
mjon
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Thanks for the reply and the link mjon. I am going to try one if those
Alun