Luminous Landscape Forum
Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: rogerxnz on February 17, 2008, 07:20:19 pm
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I'm filling in time before my Aptus 17 arrives by wondering how I will handle the great dynamic range of the sensor (12 stops claimed). With transparencies, I base the exposure on a 5-stop dynamic range and give the brightest important highlight 2.2 stops more exposure than the handheld spot meter (Minolta) displays. That is how the meter is programmed by Minolta.
So, if meter reads 17.2EV, I use 15EV as the base exposure, which I might adjust for other circumstances.
If the DB has 12 stops dynamic range, do I expose the brightest highlight 6 stops more than the meter indicates? In the above example, do I use 11.2EV, say, 11EV?
Your comments would be appreciated. In case it is relevant, I will be using a Hasselblad V system wit the back.
Roger
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If the DB has 12 stops dynamic range, do I expose the brightest highlight 6 stops more than the meter indicates? In the above example, do I use 11.2EV, say, 11EV?
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Why use a meter at all? The DB's histogram is your new best friend.
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... and much more precise than any meter: a "zone system" metering of 1st class, better you could not have it.
Best regards,
Thierry
Why use a meter at all? The DB's histogram is your new best friend.
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I expected that I would use a meter initially, to get a starting point. I know there are "old hands" who can estimate exposure to within half a stop but I have never bothered learning that "technique". I have to look through my meter viewfinder to work out what the hell I stopped to photograph.
Why use a meter at all? The DB's histogram is your new best friend.
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Roger,
the histogram IS your lighting meter, and a much more precise than your handheld one.No need to estimate, you can measure any single point directly in your histogram, respectively adjust it if necessary.
Thierry
I expected that I would use a meter initially, to get a starting point. I know there are "old hands" who can estimate exposure to within half a stop but I have never bothered learning that "technique". I have to look through my meter viewfinder to work out what the hell I stopped to photograph.
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Deleted.
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The Aptus has the best histogram thinkable, besides that it also gives a numerical read-out on how much you are off and which way. It does so in 3 colors, red (way off) yellow (off but usable) and green (spot-on). It is displayed in stops, eg. -0.5 for halve a stop under, etc...
You can overlay the histogram and exposure warning on top of your image, it is big and very easy to read precisely.
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You have roughly 2 stops above middle grey before you blow channels. But yeah, use that histogram. I always use a meter to set lights and then the histo to fine tune things. I light and meter like I did for slide film. Increased dynamic range over 35mm digital and slide film appears to be in the shadows.
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That's not very much headroom. If that is truly the case in the RAW data, then the ISO sensitivities are probably a bit understated. What is called "ISO 100" is probably ISO 200 over-exposed by a stop, using a standard of 3.5 stops of highlight headroom in the most sensitive channel (almost always green), as is used in most DSLRs (up to 4 stops, actually in some models).
More accurate stats on various cameras would be useful. You can't trust the MFRs most of the time, as their logistics are generally market-driven. What is needed is the true metered ISO at 0 EC, and the headroom above metered gray in the RAW data, and in the manufacturer's JPEGs or TIFFs if provided.
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Deleted
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The Aptus has the best histogram thinkable, besides that it also gives a numerical read-out on how much you are off and which way. It does so in 3 colors, red (way off) yellow (off but usable) and green (spot-on). It is displayed in stops, eg. -0.5 for halve a stop under, etc...
You can overlay the histogram and exposure warning on top of your image, it is big and very easy to read precisely.
[a href=\"index.php?act=findpost&pid=175587\"][{POST_SNAPBACK}][/a]
...and there's also a spot meter so you can pick any point in the scene and it'll show you the exact exposure and where it sits on the histogram. This is true whether you shoot into a CF card or tethered.
Yair
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I reckon that your gain in dynamic range will be mostly in the mid to lower tones.
JP
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I just recent questioned Leaf in Hong Kong on exposure for my A65, following was their reply. I think it clarifies a bit;
1. "+2" is the white point. Pick a point of white spot and the reading should be "+2". Then your exposure is at the normal range.
2. In digital back, we get the largest dynamic range already. In theory, the overexposure is "+2.5" and underexposure is "-4.0". All the data out of this range are hardly to retrieve. If you still need to retrieve the "shadow details", you can push up and get up those data in the range of "-5.0" or even "-6.0". But those information for sure would be very noisy. So, when you are shooting, you can use the "exposure alarm" to check would those information falling into your target objects or not.
3. "12 f-stops" DR is counting from "+3.0" to "-9.0". This is the specification from CCD sensor and the A/D converter. By theory, we set "+2" as the highlight point, "+0" as the mid-point and "-4" as the shadow point. From the histogram, you can see the curve setting is starting from the "+3" to the far end. If you don't adjust the toning curve, the recommended range is from +2.5 to -4.0. But, you can adjust the curve freely and retrieve the information from those out of normal range area. This is the power of the "12 f-stops" DR.
In contrast to the DR in traditional film, those out of normal range area are always missing details (physically washed out in film processing). So, the DR of film is only up to 5 f-stop.
Regards
Anders
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I reckon that your gain in dynamic range will be mostly in the mid to lower tones.
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What is your definition of DR? DR is only concerned with the maximum signal and the lowest usable signal. It has no concern for in-between ranges.
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Deleted.
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As the initiator of this thread, I am not keen to kill it. I am getting very useful info and an understanding of what 12-stops DR means.
I started the thread because I was puzzled as to where I should place highlights with a change from transparency film (5-stop DR) to a MFDB (12-stop DR). I now understand that the benefits of DBs' greater DR occur in the midtones and shadows; that I should place the highlights about +2EV from the meter reading and that exposure should be checked on the the histogram and refined as may be necessary.
I fail to see what harm there is in letting the discussion continue--the most recent comments have been just as valuable, if not more so, than the earlier ones. How can further knowledge/comment be "not good"?
Lets kill this thread. I see where it is going and its not good.
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What is your definition of DR? DR is only concerned with the maximum signal and the lowest usable signal. It has no concern for in-between ranges.
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exactly
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Lets kill this thread. I see where it is going and its not good.
[a href=\"index.php?act=findpost&pid=175744\"][{POST_SNAPBACK}][/a]
Perhaps the Red Cross can set up a camp right next to this thread, just in case.
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It does have all the elements to go totally into the wrong direction, DR, ETTR, comparison to film and comparison between DSLR & MFDB.
Sofar so good
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A few months back I started a thread about whether the ETTR technique was necessary for MFDB or not and I think my question was similar to yours. Correct exposure technique and a lot of the stuff coming up like DR, etc was discussed in that thread. Link below.
http://luminous-landscape.com/forum/index....showtopic=20673 (http://luminous-landscape.com/forum/index.php?showtopic=20673)
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Sorry to come in so late
When you calibrate your meter with the 18% gray in the middle of the histogram you will have a very good starting point.
When you want to light on the edge use + 2 1/3rd for white and - 4 1/3 for black.
The file will register white till about 3 stops and blacks to app 5 stops down, but especially shadow recovery can be noisy.
For PHOTOGRAPHIC white (in print) I use 2 stops over and 4 stops down.
It's easy calculated.
if middle gray is 18%
1 stop higher is 36
1 stop higher is 72 (or white with some structure)
1/3 stop higher is 96 (or white without detail and structure)
Down it's
1 stop lower is 9
1 stop lower is 4.5
1 stop lower is 2.2
1 stop lower is 1.1 ( or black with almost no structure)
It's something I picked up from Dean Collins when he explained light in photographic print values instead of the zone system.
I find this method to be so much clearer to understand for someone who hasn't got a clue about the zone system and has to light a scene.
The leap Aptus does recover some detail to + 2.5 stops but after that it's very very tricky.
According to the histogram in leaf capture you would have an exposure to +3 and -11 (the bottom one I'm not sure about).
When you shoot you can see this also as detail and when recovering it's there but it's noisy and bad looking.
Also in leaf capture there are two lines in the histogram clearly marking the -4 1/3 and 2 1/3 stop areas, meaning photographic/print black and white.
When you keep those two everything will print fine.
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I just started using a P30/645AFD II a couple of months ago and coming from a 5D this is what I've learned/my technique.
1. Let the camera calculate the exposure and take a first shot
2. Review the histogram
3. ETTR on the second shot (usually +.7)
4. Convert the raw, preserving highlights and shadows
5. If the scenes dynamic range is less than that of the cameras (typical) it will look a bit washed out so in PS I fix it with a "hockey stick" shaped curve to compress the shadows (where the extra DR is) and increase the contrast.
Hope this helps
Marc
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"hockey stick" shaped curve
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Thanks, Marc. I would like to confirm what you mean by "hockey stick shaped curve." I recall a hockey stick is like a [good behaviour] tick. Is that the shape you mean? Your curve starts a bit above the bottom of the grid, goes down to the bottom and then goes up to the top of the grid.
I guess, the "business end" of the stick is on the left of the "shaft/handle"?
Or have I misunderstood?
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Thanks, Marc. I would like to confirm what you mean by "hockey stick shaped curve." I recall a hockey stick is like a [good behaviour] tick. Is that the shape you mean? Your curve starts a bit above the bottom of the grid, goes down to the bottom and then goes up to the top of the grid.
I guess, the "business end" of the stick is on the left of the "shaft/handle"?
Or have I misunderstood?
[a href=\"index.php?act=findpost&pid=177188\"][{POST_SNAPBACK}][/a]
In photoshop the curve is as follows
4 points in the curve described as input/output
0/0, 21/4, 35/17, 255/255
looks like a hocky stick pointed to the left
Marc
PS if it is a high DR scene and you need the shadow detail don't apply the curve, but if it is a normal daylight scene (or less DR) this will compress the shadows and increase the mid tone contrast so the image doesn't look so washed out.