Friday, October 28, 2011

...and it is all -ober!

The judging for projected images this month was fairly tough. A lady who was quite forthright that a good part of her assessment was subjective only awarded three Honours over the three grades and two of those to A Grade. I can not dispute her assessment of my two images, particularly given her starting point. The difference between depicting “Dance” as a topic and the depiction of “movement in dance” that came from at least three other entries, and my attempt to convey the “energy” involved became something of a theme for the evening. I think I was given “Merit” for both. That equates pretty much as “average”.

That was followed by a brief exposition on histograms, DR, and the difference between visual sensitivity and mechanical sensitivity. Interesting, especially since it explained something that I had not been able to work out. I generally shoot in RAW and have found that sometimes the extreme ends of the histogram contain unexpected detail. The reason you will see, no doubt, is that the JPEG version has sensitivity of just four stops. The RAW file is sensitive to about 1.5 stops either side of the JPEG range, giving a total of roughly 7 stops between total black and total white. Hence the DR of a RAW image can be expanded simply by wringing the two ends of the histogram out into the “middle” portions of the extremes on the JPEG scale.

The reshoot of the mask series has been redone. I have looked at the results briefly. There are issues that need to be resolved – and in the following order -

The quartz-iodide 500W tube I am using for lighting is completely OTT. Far too hot. I don’t want to have to get filters to correct so I am going shopping for eco-bulbs which I have discovered carry a K rating. The ones we use for lighting at home are generally 4500K, much less yellow than the QI tube but still well below sunlight. I know there is a 5500K range as I have seen it mentioned several times. I need go look.

I need to develop a means of stretching the backcloth over its width at tabletop height. It will work quite well as a backing but it is getting shade variations still – quite badly. At this stage I think a couple of loop tags sewed carefully to the edge on each side will suffice. CF or dowel stretchers to follow. Rolling the cloth onto a larger dowel works well. Happy with that I am.

The camera needs further “investigation”. I need to find the manual and read up on the multiple exposure function and whether it includes automatic compensation for the number of exposures. Being film and not digital I can not blame the camera for “averaging” if I am using it on Manual. I tried spot metering this time on the black. I seems to have made some difference, but not enough as the backcloth did not burn out as I wanted.

I just went took a look back over the last couple of months. One of the things in my head that might help with this whole problem of getting the multiple exposures how I want them is actually to backlight the backcloth – put lights behind the backcloth, effectively turning that part into a direct softbox..

The other thing that needs consideration is that of shadows. With only the one strong light, I get a fair shadow on the opposite side of the object. Absolutely not needed. So if I get the 5500K bulbs, I will need about 1500 watts worth – 1000w from the back, 250w each side. I also have in mind the construction of a softbox. That would not resolve the shadow problem but might help in the overall lighting scheme.

I am also trying to determine the actual difference between the various settings – rough eyeball judgement of the negs is not sufficiently accurate. I am going to use a borrowed Dimage scanner to get the film onto disc so I can play around with it.

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