Chroma Noise

I always shoot around ISO400 with my T1i, I haven't even taken any shots with the new jansjo lights yet because I have had so much going on around here and haven't had time to do so

In digital photography, my understanding of the ISO is that it's somewhat artificial. By that I mean, your sensor is able to "count" a certain number of photons per unit time per pixel. At a high ISO, it counts fewer of these photons and (in silico) predicts the expected number it would have counted at a lower ISO (e.g., ISO 100). I believe that, as your ISO increases, the more in silico prediction (or amplification) that occurs by the processor to "guess" how many photons the sensor would have detected at the proper exposure time.

When this "prediction" occurs at extremely high ISO values, the noise observed in dark areas is caused by the imprecision in the boosting of these photon counts. I think of it as, if I count 1 photon (very dark area) at ISO1600, when I "boost" that to an equivalent lower ISO, it happens in integer increments. Thus, the difference between 1 photon in a dark area, and 2 photons in a dark area at ISO1600 is magnified when boosted to give proper exposure. I hope that makes sense.

In the "studio" setting, with continuous lighting and with a stable rig, I only use ISO100 settings. If I understand it correctly, any improvement in contrast at ISO400 would be achieved at the loss of dynamic range. Again, I'm relatively new at coin photography, so I'm more asking if I'm understanding this correctly...? Thoughts? Is my thought process flawed?

Gotcha. Keep in mind, you're a much more linear thinker than I am - I have to force myself into unfamiliar patterns to approach anything logically.

The Componon will be arriving today, so we'll see what's going on here.

OK. First impressions of the Schneider Componon-S 100/5.6:

1) This lens is incapable of focusing on a Morgan-sized coin at below 1:1, at any distance. I handheld the whole rig, backing it away from the coin and simply cannot achieve focus fullsize on the sensor. It's an order of magnitude better than the Spiratone in terms of sharpness, though - I can't wait to do some mag shots with it. It just doesn't have the image circle to encompass a Morgan unless I'm missing something.

2) It has a much more forgiving focus range than the 75ARD when presented with a coin it can show appropriately, in my case the Mercury dime which has been posted here. The "sweet spot" at a mechanical f/8 setting is a range, rather than a "fiddle and try to get it perfect" like the Rodenstock.

3) It cannot achieve the ultimate resolution of the Rodenstock. It's still in a different league than any "standard" lens I've used before.

4) The chroma noise is unchanged; the images I'm posting here are relieved of chroma to the same degree as my 75ARD shots. It's not the lens.





I couldn't be happier that I bought it.

Heck, the only way I could achieve focus on the dime was to remove the plate from the base and set the coin on the table. At that, both the bellows and vertical adjustment were fully extended.

Dave, maybe you have already read this write-up for the T2i, but I found it useful. I just stumbled upon it this morning. It's very informative.

http://www.imaging-resource.com/PRO...IIMATEST.HTM


One small piece from the article: "The Canon T2i offers four high ISO NR settings: Disable, Low, Standard and Strong. Although it's called high ISO NR, it is applied at all ISOs."

Have you experimented with the High ISO Noise Reduction settings at all in your shots? Worth at least a look if not.