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  1. #11

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    You also get a very useful extension of dynamic range of the paper negative by pre-flashing. I pre-flash my Ilford VC so that when I develop it, a sheet that has not been exposed in camera would develop so there is just a fraction of darkening compared to an area covered during the pre-flash. I spent quite some time characterising Ilford VC and many other VC papers seem to be similar. I meter using a digicam (not through any filters) and then rate my pre-flashed paper as EI 20 if I am not using filters, or EI 6 if I am going to use a yellow filter (the reduced paper speed also takes any filter effects into account). The paper ratings are assuming you are developing the negative to completion and not pulling it early from the developer. In daylight and without the yellow filter, the paper will capture plus/minus 2.5 stops relative to the metered shade and with the yellow filter, plus/minus 4 stops are usable, however the highlights are going rather non-linear.

    For very long exposures, you will also need to correct for reciprocity failure. e.g. if 30 sec metered, use 40 sec; 1 min goes to 1min 30; 2 min goes to 3:20; 4min goes to 8 min; 8 min goes to 20 min; 17min goes to 1 hour; 33 min goes to 2 hours. I regularly make multi-hour exposures, but you do get higher contrast results.

    Best regards,

    Evan

  2. #12
    aaronmichael's Avatar
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    Nov 2010
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    Quote Originally Posted by banana_legs View Post
    You also get a very useful extension of dynamic range of the paper negative by pre-flashing. I pre-flash my Ilford VC so that when I develop it, a sheet that has not been exposed in camera would develop so there is just a fraction of darkening compared to an area covered during the pre-flash. I spent quite some time characterising Ilford VC and many other VC papers seem to be similar. I meter using a digicam (not through any filters) and then rate my pre-flashed paper as EI 20 if I am not using filters, or EI 6 if I am going to use a yellow filter (the reduced paper speed also takes any filter effects into account). The paper ratings are assuming you are developing the negative to completion and not pulling it early from the developer. In daylight and without the yellow filter, the paper will capture plus/minus 2.5 stops relative to the metered shade and with the yellow filter, plus/minus 4 stops are usable, however the highlights are going rather non-linear.

    For very long exposures, you will also need to correct for reciprocity failure. e.g. if 30 sec metered, use 40 sec; 1 min goes to 1min 30; 2 min goes to 3:20; 4min goes to 8 min; 8 min goes to 20 min; 17min goes to 1 hour; 33 min goes to 2 hours. I regularly make multi-hour exposures, but you do get higher contrast results.

    Best regards,

    Evan
    Thanks for the great reply Evan. I've preflashed a couple times but had no luck with it, think I just did it wrong. I'll do some more research and try it out again.

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