Re: [pinhole-discussion] Polaroid Reciprocity
Chris, excellent point. But thanks a lot, now you've got me taking issue with Travis. Guillermo is geek alright, but he is NO Whatever geek. From what I've seen, he definitely is an Everyever geek. And when it comes to reciprocity, that beats your run-of-the-mill KnowNothing geek (my category) hands down. The main reason some of us are here. Mike Healy - Original Message - From: Chris Peregoy To: pinhole-discussion Sent: Wednesday, October 30, 2002 4:33 PM Subject: RE: [pinhole-discussion] Polaroid Reciprocity = Original Message From Jeff Dilcher dilc...@hiddenworld.net = On Wednesday 30 October 2002 02:55 pm, ROBERTSON,TRAVIS J wrote: whatever geek Trying for most un-cool subscriber post? You have my vote... Whats nice about this group is that its full of all types of geeks. Some are math geeks, some are techno geeks others are aesthetics geeks. Most of us probably have multiple traits. I for one am not a math geek, but I have saved the past few formulas because I do wish to learn how to use them some day. I like all the different types and styles of pinholers here though sometimes questions or answers or statements tick me off. I think its best to wait and let things calm down and let my response evolve in my head before sending out a reply. Each of us is here for our own reasons and each response should acknowledge that. I'm going to take Travis's response to mean that he's in awe of Guillermo's response. Chris Peregoy pere...@umbc.edu http://userpages.umbc.edu/~peregoy ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.???/discussion/
RE: [pinhole-discussion] Polaroid Reciprocity
= Original Message From Jeff Dilcher dilc...@hiddenworld.net = On Wednesday 30 October 2002 02:55 pm, ROBERTSON,TRAVIS J wrote: whatever geek Trying for most un-cool subscriber post? You have my vote... Whats nice about this group is that its full of all types of geeks. Some are math geeks, some are techno geeks others are aesthetics geeks. Most of us probably have multiple traits. I for one am not a math geek, but I have saved the past few formulas because I do wish to learn how to use them some day. I like all the different types and styles of pinholers here though sometimes questions or answers or statements tick me off. I think its best to wait and let things calm down and let my response evolve in my head before sending out a reply. Each of us is here for our own reasons and each response should acknowledge that. I'm going to take Travis's response to mean that he's in awe of Guillermo's response. Chris Peregoy pere...@umbc.edu http://userpages.umbc.edu/~peregoy
Re: [pinhole-discussion] Polaroid Reciprocity
On Wednesday 30 October 2002 02:55 pm, ROBERTSON,TRAVIS J wrote: whatever geek Trying for most un-cool subscriber post? You have my vote...
Re: [pinhole-discussion] Polaroid Reciprocity
Is this code for something? Does everybody else in alternative processes already know what this means? Am I just out of loops? Mike Healy - Original Message - From: ROBERTSON,TRAVIS J To: 'pinhole-discussion@p at ???' Sent: Wednesday, October 30, 2002 12:55 PM Subject: RE: [pinhole-discussion] Polaroid Reciprocity whatever geek -Original Message- From: Guillermo [mailto:pen...@rogers.com] Sent: Tuesday, October 29, 2002 8:28 PM To: pinhole-discussion@p at ??? Subject: Re: [pinhole-discussion] Polaroid Reciprocity - Original Message - From: Jason Russell jruss...@wishtv.com The corrected time you gave me worked very well. Thank you! However, I want to clarify one thing... Did you go to the Polaroid website to get the numbers to plug into the WinCurveFit program? Did you just pull the numbers from the displayed graph and plug them into the program and extend the curve? Is that how that works. Jason, altho I could have used the graph to get some indicated versus corrected values, that graph is just too coarse and since some values are already given in the Reciprocity Performance table, that's what I used. Now, that table (or graph) gives you corrected values in terms of extra stops of Exposure Adjustment, so we need to translate the indicated exposures to corrected exposures in seconds. For full stops it is easy, you double the indicated exposure for each stop of adjustment, but what about, for instance, the corrected exposure for an indicated 16 secs and an adjustment of +1 2/3 stops? To do it, you have to use the following equation: I = indicated time T = corrected time n = exposure correction in stops ^ = raised to the power of (need scientific calculator to do it, I use CALC98, freeware program downloadble here http://www.calculator.org/download.html) T = I * (2 ^ n) In the case of 16 secs and 1 2/3 stops adjustment, it would be: T = 16 * (2 ^ 1 2/3) T = 16 * (2 ^ 1.) T = 16 * 3.17465 T = 50.79 secs Once you have all the corrected values in seconds, feed the indicated and corrected values to the WinCurveFit program. I have to mention that I don't bring a calculator with me when I go out to make exposures, I prefer to make a graph, very much like this one http://www.kodak.com/global/en/professional/support/techPubs/f9/f002_0062gc. gif and use that to find corrected times. Guillermo ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.???/discussion/ ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.???/discussion/
Re: [pinhole-discussion] Polaroid Reciprocity
Is this code for something? Does everybody else in alternative processes already know what this means? Am I just out of loops? Mike Healy - Original Message - From: ROBERTSON,TRAVIS J To: 'pinhole-discussion@p at ???' Sent: Wednesday, October 30, 2002 12:55 PM Subject: RE: [pinhole-discussion] Polaroid Reciprocity whatever geek -Original Message- From: Guillermo [mailto:pen...@rogers.com] Sent: Tuesday, October 29, 2002 8:28 PM To: pinhole-discussion@p at ??? Subject: Re: [pinhole-discussion] Polaroid Reciprocity - Original Message - From: Jason Russell jruss...@wishtv.com The corrected time you gave me worked very well. Thank you! However, I want to clarify one thing... Did you go to the Polaroid website to get the numbers to plug into the WinCurveFit program? Did you just pull the numbers from the displayed graph and plug them into the program and extend the curve? Is that how that works. Jason, altho I could have used the graph to get some indicated versus corrected values, that graph is just too coarse and since some values are already given in the Reciprocity Performance table, that's what I used. Now, that table (or graph) gives you corrected values in terms of extra stops of Exposure Adjustment, so we need to translate the indicated exposures to corrected exposures in seconds. For full stops it is easy, you double the indicated exposure for each stop of adjustment, but what about, for instance, the corrected exposure for an indicated 16 secs and an adjustment of +1 2/3 stops? To do it, you have to use the following equation: I = indicated time T = corrected time n = exposure correction in stops ^ = raised to the power of (need scientific calculator to do it, I use CALC98, freeware program downloadble here http://www.calculator.org/download.html) T = I * (2 ^ n) In the case of 16 secs and 1 2/3 stops adjustment, it would be: T = 16 * (2 ^ 1 2/3) T = 16 * (2 ^ 1.) T = 16 * 3.17465 T = 50.79 secs Once you have all the corrected values in seconds, feed the indicated and corrected values to the WinCurveFit program. I have to mention that I don't bring a calculator with me when I go out to make exposures, I prefer to make a graph, very much like this one http://www.kodak.com/global/en/professional/support/techPubs/f9/f002_0062gc. gif and use that to find corrected times. Guillermo ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.???/discussion/ ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.???/discussion/
Re: [pinhole-discussion] Polaroid Reciprocity - new question
Hi all, I will be using polaroid type 669 in a pinhole utilizing daylight. Has anyone done any color correction tests so that I may bave this information before I start? Specifically, what gel do I need to correct for any overall color casts? My goal is to have the pics as neutral as possible. Thanks in advance, Don __ Do you Yahoo!? HotJobs - Search new jobs daily now http://hotjobs.yahoo.com/
Re: [pinhole-discussion] Polaroid Reciprocity
Guillermo, The corrected time you gave me worked very well. Thank you! However, I want to clarify one thing... Did you go to the Polaroid website to get the numbers to plug into the WinCurveFit program? Did you just pull the numbers from the displayed graph and plug them into the program and extend the curve? Is that how that works. Thanks again! Jason Russell WISH-TV Indianapolis, IN If you go any faster we're gonna travel back through time. - Original Message - From: Guillermo pen...@rogers.com To: pinhole-discussion@p at ??? Sent: Tuesday, October 29, 2002 5:06 PM Subject: Re: [pinhole-discussion] Polaroid Reciprocity - Original Message - From: Jason Russell jruss...@wishtv.com Will the equation change with different types of film? The equation is just a math model of the reciprocity correction curve, the latter is just a graphic representation of the discrete values, either given by manufactures (like the ones given by Polaroid for the film in question - Polapan type 72) or obtained by us thru experimentation. Since each film has its own reciprocity characteristics, each film would have its own equation. Or do I just plug the indicated time into the equation to get a starting point? If it does change, which numbers will be different and how do I figure them out All the coefficients change. You can find them by doing a Regression analysis of the known reciprocity correction values, I use the Least Square polynomial method, here is a hint on how to do that: http://www.efunda.com/math/leastsquares/lstsqrmdcurve.cfm , for those of us confused by the above, using a program like WinCurveFit http://www.krs.com.au/wcf.html is a good thing, that is what I used to give you the answer BTW. Guillermo ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.???/discussion/
Re: [pinhole-discussion] Polaroid Reciprocity
- Original Message - From: Jason Russell jruss...@wishtv.com Will the equation change with different types of film? The equation is just a math model of the reciprocity correction curve, the latter is just a graphic representation of the discrete values, either given by manufactures (like the ones given by Polaroid for the film in question - Polapan type 72) or obtained by us thru experimentation. Since each film has its own reciprocity characteristics, each film would have its own equation. Or do I just plug the indicated time into the equation to get a starting point? If it does change, which numbers will be different and how do I figure them out All the coefficients change. You can find them by doing a Regression analysis of the known reciprocity correction values, I use the Least Square polynomial method, here is a hint on how to do that: http://www.efunda.com/math/leastsquares/lstsqrmdcurve.cfm , for those of us confused by the above, using a program like WinCurveFit http://www.krs.com.au/wcf.html is a good thing, that is what I used to give you the answer BTW. Guillermo
Re: [pinhole-discussion] Polaroid Reciprocity
Guillermo, Will the equation change with different types of film? Or do I just plug the indicated time into the equation to get a starting point? If it does change, which numbers will be different and how do I figure them out? Thanks Jason Russell WISH-TV Indianapolis, IN If you go any faster we're gonna travel back through time. - Original Message - From: Guillermo pen...@rogers.com To: pinhole-discussion@p at ??? Sent: Monday, October 28, 2002 6:43 PM Subject: Re: [pinhole-discussion] Polaroid Reciprocity - Original Message - From: Jason Russell jruss...@wishtv.com I was wondering if anyone could help me with Polaroid Reciprocity. I just recently started shooting with a Santa Barbara (2 inch Super Wide) with a Polaroid back. Right now I'm shooting with Polapan 400 BW (72). I've done most of my shooting outside and the exposures have all been less than six seconds. I wanted to try shooting inside under much lower light. I'm just not sure how much I need to compensate for reciprocity. I checked out the info on Polaroid's site, but I'm still a unclear. Has anyone else shot with this film or a similar film that could give me an idea of how much time to add. The shot I want to shoot right now, by my calculations is about 2 and a half minutes without compensating for reciprocity. Jason: I have not used the film, nevertheless here is my suggestion: Short answer: for indicated 2.5 minutes you should give 17 minutes 3 secs. Long answer: As you can see on the Reciprocity Performance chart, the effective film speed decreases (as expected) as the indicated exposure time increases, the exposure adjustment column tells you how many stops you should increase the indicated time. For 4 secs, for instance, the exposure adustment is 1 stop, that means you should double the time to 8secs. I made some math calculations (best curve fit) and they predict that when the indicated exposure time is 150secs (2.5minutes), the effective film speed will be ISO-58.6, which in turn will need an exposure adjustment of 2.77 stops, for a total of 1023secs or 17 minutes 4 secs (150 x 2^2.77 = 1023). If you want some other times, use the following formula: T = corrected time I = indicated time * = multiplication sign T = ( 0.021 * I * I ) + ( 3.708 * I ) - 4.89 CAVEAT: the above suggestion is just an educated starting point based on the Polaroid published information, YMMV. Guillermo ___ Post to the list as PLAIN TEXT only - no HTML Pinhole-Discussion mailing list Pinhole-Discussion@p at ??? unsubscribe or change your account at http://www.???/discussion/
[pinhole-discussion] Polaroid Reciprocity
I was wondering if anyone could help me with Polaroid Reciprocity. I just recently started shooting with a Santa Barbara (2 inch Super Wide) with a Polaroid back. Right now I'm shooting with Polapan 400 BW (72). I've done most of my shooting outside and the exposures have all been less than six seconds. I wanted to try shooting inside under much lower light. I'm just not sure how much I need to compensate for reciprocity. I checked out the info on Polaroid's site, but I'm still a unclear. Has anyone else shot with this film or a similar film that could give me an idea of how much time to add. The shot I want to shoot right now, by my calculations is about 2 and a half minutes without compensating for reciprocity. Thanks in advance for your help. Jason Russell WISH-TV Indianapolis, IN If you go any faster we're gonna travel back through time.
