Re: Step Wedge

Hey Sandy,

Thanks for the responses to the group- I hadn't even considered flare
factor before I brought the topic up.
My step wedge is hand calibrated by stouffer- at least it looks like it
is. They wrote in ballpoint pen on the
sleeve the actual densities of each wedge- I'm assuming someone must
have actually measured it personally.
If that is the case, I am guessing the density values must be total
transmittance, including the substrate,
but I might be wrong about that.

-Jeff

Sandy King wrote:

>
> For some reason I had it in mind that you wanted to compare of
> different film, or perhaps of different developers. For what you have
> in mind I think the method you suggest is certainly valid.
>
> On a practical note, remember to take into account the B+F density of
> the step wedge. This should be about log 0.05, or about 1/3 of a stop,
> so you should probably increase your metered exposure by about this much.
>
> Sandy
>
>
>
>> I wasn't really planning on doing any hard core film comparisons with
>> the
>> test- just basically wanted to see if my shutter and lens and lightmeter
>> are giving me close to the density that I am hoping to achieve when I
>> make
>> an exposure. Also, I was hoping to plot the curves using a few
>> different
>> development times to visualize the effects of plus and minus times.
>>
>> Since my negs are destined to be scanned, and corrected, and ultimately
>> digitallly printed on film for contact printing, if my results are a
>> 1/10
>> stop off here or there, I could probably still sleep!
>>
>>
>>
>> On Thu, Nov 11, 2004 at 03:36:39PM -0500, Sandy King wrote:
>>
>>> Etienne wrote:
>>>
>>> >
>>> >As an abstract exercise (especially for someone who, like me,
>>> occasionally
>>> >whips up his or her own negative emulsion for fun), it's
>>> interesting to
>>> >know what the film does, on its own. But when I load my holders,
>>> I'm after
>>> >the most direct understanding of what my negatives are going to
>>> look like
>>> >when they come out of the Jobo, and rolling all of the relevant
>>> practical
>>> >factors into the material characterization gives me this.
>>> >
>>>
>>>
>>> But my point is not that practical testing in the camera is not
>>> relevant, but simply that it is invalid as a means of comparing EFS
>>> of different films. For that you need a system with a common light
>>> source and some control that permits repeatable exposures to an
>>> accuracy of about 1/10 of a stop.
>>>
>>> Sandy
>>>
>
Received on Thu Nov 11 20:55:01 2004