whitestone

<p>With my MKII and scenes that contain a lot of near white (but not over exposed to the point of clipping) I notice a significant amount of noise in the shadow areas at ISO 100. In scenes that have fewer pixels to the right, the noise in the shadows is quite low. I'll try to post an example soon.</p>

<p>I have the 100 f2.8 and the 135 f2. For tight portraits, I go with the 100 f2.8. The 135 gets soft at f2 and f 2.8 at the near limit of focus. Also, at f2 and f2.8 at close distances the DOF of the 135 is so thin that I rarely get a portrait that I like.</p>

<p>Another consideration is focal length. My copy of the lens produces the sharpest results at 50 to 65 mm focal length.</p>

<p>I found that just running the registry sweeper would often fix my scanner problem (hanging in the middle of a scan).</p>

<p>Here's another data point for you:<br>

http://picasaweb.google.com/lh/photo/pjNmF1rF6K-GkrLTqYoL6Q?feat=directlink<br>

(Click on the magnifying lens to see the uncompressed view.)<br>

No EXIF data; it is a Coolscan5000 scan of Fuji Astia. Lens is the 28-70 F2.8, purchased two months ago.</p>

<p>I have the 85 f1.8, 100 f2.8, and 135 f2, and the 100 mm macro is my goto lens for portraits.</p><div></div>

<p>batteryBob.com has them for $6.14, free shipping. I just ordered one today. (I have no affiliation with batteryBob. ) <br /> </p>

<p>Patrick,<br>

You are very generous to make this offer. (And thanks for all the helpful information you offer!)<br>

-Rob</p>

<p>I think both camps would say that the ADC output tells you which portion of the input range the exposure falls into (the portions being equal to range/2^n, where n is the bit depth of the ADC).</p>

<p>The matter of difference is: what is that range? One camp says that the range can be from any max to any minimum (i.e. any arbitrary range). The other camp says the range can be from any arbitrary max to a minimum of max/2^n.</p>

<p>I think this thought experiment might settle things. Consider the simple limiting case of a 1-bit ADC. Let's assume we have a 5 stop scene, a 5 stop imaging sensor producing an output of 0 to 1 volts, and a 1-bit ADC with an input range of 0 to 1 volts. Any pixels in the highest of the 5 stops will result in the sensor producing a voltage between 0.5 and 1 volts which will result in the ADC outputting a value of 1. Any pixels that are found in the lower 4 stops will result in the sensor producing a voltage between 0 and 0.5 volts which will result in the ADC outputting a 0. I think we are all agreed on this.<br /> <br /> What does the ADC output of 1 represent? Pure white?<br /> Now for the important question: What does the ADC output of 0 represent?<br /> <br /> According to Bernie's line of thought, the 0 would represent the second highest stop, and the resulting print will be very high key. But, if the ADC output is interpreted to match its input, then the 0 output should be interpreted as black (or the darkest stop), resulting in black and white ortho-litho print (with the full 5 stop range, although with no gray tones in the middle).</p>

<p>(Actually, I'm not sure where the dividing line typically falls for an ortho-litho image -- just below the highest stop, or in the middle stop?)</p>

<p>I have a 135/2.0, and I am caught up in the idea that portraits (face framed) are best done at 4.0 or greater.</p>

<p><em>Bernie wrote: If I handed you an 8 bit print created from an 8bit ADC (with the specs of all my previous examples, including no noise for simplicity), there is no way when you looked at that print that you could tell how many stops where encoded to level 0 (ie. black). The only useful information you could tell from that print is that it had 8 stops of exposure range. It could have been of a 8 stops scene, a 9 stop scene, or a 50 stop scene. There would be no way for you to tell. This is what I have been getting at all along.</em></p>

<p>I think this is wrong (and this gets to the heart of the matter). The number of stops I could distinguish is determined by the range that the 8-bit print is capable of displaying. If the 8-bit ADC is fronted by an imaging sensor capable of recording a 50 stop scene and the printer is capable of printing over 50 stops, then the max value that travels through this system will represent a tone that is 50 stops greater than the tone represented by the minimum value, and this will be expressed in the print (regardless of the number of bits in the ADC).</p>

<p>I think what Bernie is saying is that when multiple stops map to the same step of an ADC then the ability to differentiate among the stops is lost (and they become essentially the same), so as far as the end result is considered those multiply-mapped stops never made it through.</p>

<p>However, as Vijay noted in above posts, when multiple stops map to the same ADC step, that step should be interpreted as the least of the stops mapped to it; thus (in Bernie's example) the 4-bit ADC still provides information pertaining to whole 8 stop input range.</p>

<p>So, a 4-bit converter only has enough resolution to distinguish among 4 stops. I'm still not sure what your definition of 'ACCURATE' is. For photographic purposes, I wouldn't say the 4 stops (let alone 8 stops) would be very accurately described with a 4-bit converter.</p>

<p>Vijay,</p>

<p>I think you looked at Helen's example incorrectly. She was mapping ADC output values (0-255) to what they might represent.</p>

<p>-Rob</p>

<p>Aww, dang Helen, I was really looking forward to see your reworking of Max's example.<br /> Also, why do you impose the 'requirement for proportionality' (i.e. linearity with offset=0)?<br>

<br /> -Rob</p>

<p>Helen,</p>

<p>You can interpret those 256 unique encodings appropriately to the input to the ADC. If the input represents a range of 1 to 100000, then interpret the the 256 unique output values as 256 numbers equally spaced from 1 to 100000.</p>

<p>-Rob</p>

<p>Max - Excellent example.</p>

<p>Helen - You seem to be not talking about the dynamic range of the imaging sensor or the input of the DAC, but the output of the DAC. This is not something that makes sense to me.</p>

<p><em>Would you call an ADC for which the output is not proportional to the input 'linear'?</em><br>

The output need not maintain a constant proportionality to the input for it to be linear. A broken ADC stuck continuously on an output of X is still linear.</p>

<p>-Rob</p>

<p>Helen,</p>

<p>You have several misconceptions in your 'point 5' above. A given number of bits can represent any range of numbers you wish. 8 bits could represent the range 0 to 65535, going by 256 for each 'increment'. This is still linear. (In fact, you could think of the output of the ADC as an index into a table of values. You can fill the table any way you wish, linear or nonlinear.)</p>

<p>Second, you can have an offset in a linear system. 'y=x+1' describes a line with an offset.</p>

<p>-Rob</p>

<p>Erica, you might not particularly want to convert from sRGB to sRGB, but if you run an action or script on an entire folder (converting to sRGB), the folder might contain some files already in the sRGB color space.</p>

> Photoshop does not like to convert from sRGB to sRGB - it will stop or crash.

 

When I run an action that includes a step to convert to sRGB, it does not crash when the file is already in sRGB.

In my own scanning I haven't noticed the dots that you are getting with Vuescan (I keep the Vuescan IR cleaning on 'light'). However, I have found Nikon Scan to be much better in general with the IR cleaning. If I have a particularly dirty slide, I go with Nikon Scan.

Can you show the same shot (Scan-001) scanned with Nikon Scan 4 so we can see the 'no problem' version?

 

BTW, Scan-001 looks as good as I ever get from my 5000ED and Vuescan.

I've never had any of my scanned slides accepted by istockphoto. They were generally rejected due to noise and grain. These were some of my best slides (Kodachrome, Velvia, and others) scanned on with a Coolscan 5000 and processed with Noise Ninja. I think istockphoto likes a more digital look.

I've used all three with the Coolscan 5000 and I cannot elicit better results from anyone one of them. Although, sometimes it seems that the Nikon software does slightly better with ICE when it comes to scratches. I use Vuescan most of the time because my Nikon software will eventually do something whacky to its registry and the only thing Nikon help desk can tell me is to run the registry cleaner and reinstall it.