[pinhole-discussion] Polaroid exposures
Hello All! I could use some help here. We just got a wonderful spring time snowfall yesterday (10") and it got me out and about with my 8x10 pinhole camera (due to the extra light reflection of the snow). I tried using Polaroid type 804 ASA 100 (first time using this film) and I can't seem to get the exposures correct. The prints keep coming out real light. Now, I could keep adjusting the time exposures but it is expensive film and I really don't want to use the whole box of film as testing material (that is, if I can help it). The camera is a normal focal length (13 inches) Leonardo 8x10 and the pinhole is F 500. Anyone out there do 8x10 pinhole Polaroids? For some reason the time charts I use for Ilford HP5 aren't working. And yes, I calculate for the difference in the film speeds. Any help would be appreciated. Oh, by the way, I let the Polaroid film warm up before processing it, and it is fresh film. Thank you in advance! Bill-
Re: [pinhole-discussion] Polaroid exposures
- Original Message - From: "The Painted Horse" > Hi Guillermo, > Thank you for your reply. Obviously, I miscalculated the math for my exposures > (*sigh*). However, just to clarify..on the calculations given below, wouldn't > it be f16 @ 1/100 secs and not 1/25 sec? 1/125 and 1/100 is for practical purposes the same thing, nevertheless, you are right, the BASE exposure for sunny open skies conditions is f/16 @ 1/100 when the emulsion you use has an ISO-100 (or EI-100 for that matter). > I'm trying to understand the basis for the formula and the 804 film is ASA > 100. Given this, wouldn't the initial exposure (not factoring in reciprocity) > then be around 10 sec. rather than 40 sec? That's right, 10 secs @ f/500 will give you the same exposure than 1/100 @ f/16 (disregarding reciprocity corrections). So using this table for 804 at Polaroid http://www.polaroid.com/service/filmdatasheets/8_10/804fds.pdf , the correction for 10 seconds would be something like 2.25 f/stops that translate to something like 48 seconds final exposure time. If you were to meter the snow (under whatever conditions of light) and get a reading of f/16 @ 1/100 secs (for instance), exposure that we now is equivalent to f/500 and 10 secs, if you give that esposure, the snow will be rendered with a grayish tone. To get it white you would need to increase the exposure around 2 stops, so the 10 seconds become 40 seconds, to which we'd need to add more time to correct for reciprocity. I think I mixed sunny/16 and metered ideas in my last message, sorry. > To answer your question I had taken a metered reading of the northern sky > rather than the snow for these exposures. The reflection was just too bright > from the snow for me to think I would get an accurate reading. The reading > came to EV16. Now, here is the part that, looking back, I can't > explain...somehow I came to an exposure of 15 minutes. EV16 is f/16 @ 1/250, I may be wrong, but I think northern sky should be at least 1 stop darker than the actual snow, which is the same to say that it is at least 1 stop brighter than 18% gray. Therefore to get snow the "right tone" you should have exposed for f/16 @ 1/125 seconds, which in turn is about the same as f/500 @ 8 seconds (uncorrected). > Please don't ask me how OK, I won't. Guillermo
Re: [pinhole-discussion] Polaroid exposures
Correction... I meant to write f16 @ 1/125 sec instead of 1/100 sec (as indicated below). Bill- The Painted Horse wrote: > Hi Guillermo, > Thank you for your reply. Obviously, I miscalculated the math for my > exposures > (*sigh*). However, just to clarify..on the calculations given below, wouldn't > it be f16 @ 1/100 secs and not 1/25 sec? I apologize if I am incorrect, but > I'm trying to understand the basis for the formula and the 804 film is ASA > 100. Given this, wouldn't the initial exposure (not factoring in reciprocity) > then be around 10 sec. rather than 40 sec? > > ___ > > Pinhole-Discussion mailing list > > Pinhole-Discussion@p at ??? > > unsubscribe or change your account at > > http://www.p at ???/discussion/
Re: [pinhole-discussion] Polaroid exposures
Hi Guillermo, Thank you for your reply. Obviously, I miscalculated the math for my exposures (*sigh*). However, just to clarify..on the calculations given below, wouldn't it be f16 @ 1/100 secs and not 1/25 sec? I apologize if I am incorrect, but I'm trying to understand the basis for the formula and the 804 film is ASA 100. Given this, wouldn't the initial exposure (not factoring in reciprocity) then be around 10 sec. rather than 40 sec? To answer your question I had taken a metered reading of the northern sky rather than the snow for these exposures. The reflection was just too bright from the snow for me to think I would get an accurate reading. The reading came to EV16. Now, here is the part that, looking back, I can't explain...somehow I came to an exposure of 15 minutes. Please don't ask me how I did this, as now that I am thinking about it, I have no idea. Nontheless, an obvious miscalculation on my part. Unfortunately the snow has melted but I will be out again this weekend to try once more. Thanks again! Bill- "G.Penate" wrote: > Bill, > Using sunny/16, your exposure should be f/16 > @ 1/25 secs. There are about 10 stops separating f/16 from f/500, therefore > for your camera, the uncorrected exposure time should be around 40 secs (2^10 > * 1/25). > > Could you tell us what's your metered or estimated uncorrected exposure time > and actual exposure times you have used? > > Guillermo > > > > ___ > Pinhole-Discussion mailing list > Pinhole-Discussion@p at ??? > unsubscribe or change your account at > http://www.p at ???/discussion/
Re: [pinhole-discussion] Polaroid exposures
- Original Message - From: > Hi this is Lonnie. > > Your exposure, I would try 4 to 8 seconds in bright snow with a bright sky, > which would probably give you a EV15 to EV16 with an ISO 100 film. > > Glad to hear you are using an 8x10 camera. I am thinking of making an 8x10 > camera out of banker boxes. Hi Lonnie, EV15 equates to an exposure of f/16 @ 1/125 secs (for instance), which pretty much confirms Sunny/16 for ISO-100. Would you care to elaborate how and exposure of 4 to 8 secs could be a proper exposure when the aperture is f/500? Thanks, Guillermo
Re: [pinhole-discussion] Polaroid exposures
Hi this is Lonnie. Your exposure, I would try 4 to 8 seconds in bright snow with a bright sky, which would probably give you a EV15 to EV16 with an ISO 100 film. Glad to hear you are using an 8x10 camera. I am thinking of making an 8x10 camera out of banker boxes. Lonnie
Re: [pinhole-discussion] Polaroid exposures
In a message dated 4/4/01 10:40:37 AM Pacific Daylight Time, paintedho...@in-tch.com writes: > The prints keep coming out real > light. Dont forget,with polaroid film,too light is too long of an exposure..try to expose the next shot for 1/2 as long.. Just my 2 cents.. Harry http://www.figurefoto.com/";>Figurefoto.com
Re: [pinhole-discussion] Polaroid exposures
Bill, Here is a brief analysis I've done: Assuming bright open sky conditions, shooting snowy scenes call for about +2 stops from whatever the meter indicates for the snow. Using sunny/16, your exposure should be f/16 @ 1/25 secs. There are about 10 stops separating f/16 from f/500, therefore for your camera, the uncorrected exposure time should be around 40 secs (2^10 * 1/25). According to Ilford HP5 reciprocity correction, 40 sec exposure should become 200 secs exposure. But according to Polaroid.com, an exposure of 40 secs needs a correction of -2.7 f/stops for 804 film. reciprocity corrections in f/stops do not equate exactly to corrections of doublings of exposure time, but assuming they do, 40 secs should become around 260 secs (2^2.7 * 40). BTW, it is not a good idea to use reciprocity corrections charts for one film and apply them to a totally different film/technology/manufacturer. Could you tell us what's your metered or estimated uncorrected exposure time and actual exposure times you have used? Guillermo - Original Message - From: "The Painted Horse" > > I could use some help here. We just got a wonderful spring time > snowfall yesterday (10") and it got me out and about with my 8x10 > pinhole camera (due to the extra light reflection of the snow). I tried > using Polaroid type 804 ASA 100 (first time using this film) and I can't > seem to get the exposures correct. The prints keep coming out real > light. Now, I could keep adjusting the time exposures but it is > expensive film and I really don't want to use the whole box of film as > testing material (that is, if I can help it). > The camera is a normal focal length (13 inches) Leonardo 8x10 and the > pinhole is F 500. Anyone out there do 8x10 pinhole Polaroids? For some > reason the time charts I use for Ilford HP5 aren't working. And yes, I > calculate for the difference in the film speeds. Any help would be > appreciated.
Re: Re: [pinhole-discussion] Polaroid exposures
- Original Message - From: > EV 15: > 1/125 @ f/16, 1/60 @ f/22, 1/30 @ f/32, 1/15 @ f/45, 1/8 @ f/64, 1/4 @ f/90, > 1/2 @ f/128, 1 sec @ f/180, 2 sec @ f/256, 4 sec @ f/360, 8 sec @ f/512. Couple of things: 1- Polaroid 804 will require reciprocity corrections for exposures above 0.04 seconds (as per polaroid.com). 2- If you meter snow and expose your film using the indications of your meter, the snow will be render as grayish instead of white. We need to increase exposure by about 2 stops so snow is rendered white. Your 8 seconds @ f/500 then become 32 seconds and those 32 seconds become about 180 seconds when reciprocity compensation is taking into account (as per Polaroid.com). Guillermo
Re: Re: [pinhole-discussion] Polaroid exposures
EV 15: 1/125 @ f/16, 1/60 @ f/22, 1/30 @ f/32, 1/15 @ f/45, 1/8 @ f/64, 1/4 @ f/90, 1/2 @ f/128, 1 sec @ f/180, 2 sec @ f/256, 4 sec @ f/360, 8 sec @ f/512.
Re: Re: [pinhole-discussion] Polaroid exposures
Hi this is Lonnie: I have a question about your answer to Bill about pinhole exposures @ f/500 with ISO 100 film. Looking at my light meter without any reciprocity corrections a sunny f/16 exposure should be about 8 seconds @ f/500. If you have heavy sun as well as bright snow I would use 4 seconds as my base for an exposure. The 8 seconds @ f/500 would be EV 15 The 4 seconds would be EV 16. Lonnie
Re: Re: Re: [pinhole-discussion] Polaroid exposures
The exposures that I sent you did not include reciprocity failure, so yes you would have to compensate for that. The exposures that I gave you were based on sunny-16. They were also based on either a 18% gray card reading or an incident light meter reading. The exposure suggestions with your film is based on sunny-16, which are pretty accurate. If you meter the light falling on a subject (indident) it is the same light that would be falling on a black subject or a white subject. If you are using a reflective meter and meter the snow, to get my readings you would have to overexpose about 2 f/stops so your snow is not unerexposed or gray. Pointing a reflective meter at any subject will read it as 18% gray. Lonnie
