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earlj
03-13-2012, 09:59 AM
http://leborddelapiscine.blogspot.com/
This looks like a great tool. I have only just installed it, but I am pretty sure that it does everything that a pinhole photographer needs. ISO values go down to .25. Reciprocity correction charts are available on the website - I just installed a dozen of them from the website, and once I figure out how to build the charts, I am sure that I can build my own for my non-standard materials. I already use a light meter app for my phone, but this one is designed specifically for pinhole.

rydolan
03-13-2012, 11:33 PM
Earl, I downloaded this app about a week ago and have found it quite useful. The reciprocity curves are such a nice feature. I have one huge complaint though, and I'd like to know if your app does the same thing: every time I open the program, the app defaults back to f/150. I'll put in all my settings, meter, and exit out to use my timer or what have you, and when I go back in, the darn thing defaults back to f/150 and I have to re-enter all of my camera's specs. It is enough of an inconvenience that I have stopped using the app.
Coincidentally however, I recently 'liked' f295 on facebook and the next day the designer of the program posted about his latest update to the software. I mentioned this problem to him in a comment but have not yet heard back from him.

earlj
03-13-2012, 11:39 PM
I will be shooting and using this app in the next few days. I will let you know what I experience. Thanks for the observations.

rydolan
03-14-2012, 12:53 AM
Have you made sense of his method of creating one's own reciprocity curve? I see what he means by editing the code for the curve file, but they seem to be just simple multipliers. (I'm referring to the example on his blog that illustrates the 2*15 multiplier)
I'd like to adapt the formula that banana_legs came up with for Ilford MGIV RC paper. I have used it with quite good results. If I remember correctly, the formula is:

T = t + [.0009(t^2.2304)]

Where (T) is the time adjusted for RF and (t) is the time suggested by a pinhole exposure chart.

I don't know how I could use banana_legs' form in the way the curves are expressed in the Pinhole Assist curve file. Maybe I'm missing something really simple here, or maybe I'm just in over my head!

earlj
03-14-2012, 07:49 AM
I have not taken the time to look at it. Perhaps I can push some numbers around after work tonight.

toniox
03-21-2012, 04:53 PM
Earl, I downloaded this app about a week ago and have found it quite useful. The reciprocity curves are such a nice feature. I have one huge complaint though, and I'd like to know if your app does the same thing: every time I open the program, the app defaults back to f/150. I'll put in all my settings, meter, and exit out to use my timer or what have you, and when I go back in, the darn thing defaults back to f/150 and I have to re-enter all of my camera's specs. It is enough of an inconvenience that I have stopped using the app.
Coincidentally however, I recently 'liked' f295 on facebook and the next day the designer of the program posted about his latest update to the software. I mentioned this problem to him in a comment but have not yet heard back from him.

I have the f250 problem too and waiting for an update, but this app is very usefull for pinholers

earlj
03-21-2012, 08:48 PM
I tested Pinhole Assist on two different occasions in the past five days, and I find it to be a very capable pinhole light meter/calculator/timer. When I open it, it displays the same settings as when I last closed it. I am running it on an iPhone 3G. With a few more refinements, it will be everything a pinhole photographer needs. Things I would like to see improved - 1. one-third stop ISO numbers (now it only includes a few commonly used film ISO numbers). I want to be able to value a film up or down from its nominal value. 2. Aperture f-values with every power of the square root of two included up to at least f1024. I have many cameras that are f350 to f500 and beyond. 3. The user should be able to enter the focal distance of the camera with the keypad, and the timer calculator should be able to handle it. Now, you have to choose from a list, and it stops at 200 mm. Obviously, the designers of this software have not shot at 12x20 inches, or maybe even 20x24 (soon, I hope).

Doug K
03-25-2012, 11:27 AM
Thanks for posting about this app. I've been wanting something for my iPhone for pinhole, and was planning on making something myself since I didn't expect anyone to produce something that has what I need. I'm just too busy right now to develop anything, let alone film. (heh) So I bought it yesterday, and at first glance seems pretty good. Hopefully they can address the issues that Earl brings up.

It doesn't look like I'll have much time in the next couple of weeks to do any pinhole photography since we're packing to move to a house we are purchasing. A house where I'll have a darkroom!!! This summer should be very fruitful for analog photography for me... of course aided by my digital tools.

toniox
03-25-2012, 03:11 PM
I am running it with an iphone 4s and the aperture is reset to f150 each time... But I encourage to use it, very handy !

toniox
03-25-2012, 03:15 PM
I was a hard user of "LightMeter by Ambertation" before, very handy too for pinhole photography.

dwerg85
03-28-2012, 12:17 PM
I experience the reset to f/150 too. but it's only the value it uses. the settings are still there. so if i jiggle the value selector it'll go back to the actual fstop.

dwerg85
03-28-2012, 02:13 PM
Not sure if i'm misinterpreting the above formula, but it's given me an adjusted reciprocity time of 9 hours for a 40 minute suggested time? That can't be right, right?

http://www.wolframalpha.com/input/?i=T+%3Dt+%2B+%28.0009*%28t%5E2.2304%29%29+and+t%3 D2400

DaveBell
03-28-2012, 04:24 PM
Not sure if i'm misinterpreting the above formula, but it's given me an adjusted reciprocity time of 9 hours for a 40 minute suggested time? That can't be right, right?

http://www.wolframalpha.com/input/?i=T+%3Dt+%2B+%28.0009*%28t%5E2.2304%29%29+and+t%3 D2400

I don't know if that's a reasonable correction factor, but the math works out.
One problem for me is that I don't know the intended units in the posted formula.
Multiplying a constant times a power of the time makes that critical.
Simply try the same evaluation, assuming minutes rather than seconds, and you get 43+ minutes (which seems too little, so??? )

Dave

rydolan
03-28-2012, 08:12 PM
dwerg, the units are in seconds, and yes, according to the formula the 40 minute exposure would compute to 9 hours. I found the formula while perusing posts for information on paper speed and have found it quite useful for adjusting exposure times which meter up to 15 mins or so. After that, the times get so long I tend to find something else to shoot or use one of my cameras that take film.
Here is the thread in which Evan (banana_Legs) explains his formula:
http://f295.f295.org/uploads/Blah.pl?m-1252335783/

I must note that I've noticed a marked improvement in my paper negatives since using Evan's reciprocity formula, however, I have never actually compared it against an identical shot that does not correct for reciprocity.
The fact that there are some very accomplished paper negative photographers on this forum who do not correct for reciprocity is reason enough to look into this issue further.

-Ryan

dwerg85
03-29-2012, 12:18 PM
I'm running some paper tests with it right now. Still kind of dumbfounded by how long the exposures get after 15 minutes. I have the plist that works in pinhole assist if anybody wants it.

rydolan
03-29-2012, 02:25 PM
Could you email it to me? Its rydolan (at) snet.net

rydolan
03-29-2012, 02:28 PM
An update for the app was released today! Claims to have fixed the f/150 issue.

earlj
03-29-2012, 02:32 PM
Reciprocity times go up a lot when the metered time is already out there. The nine hours is only 3+ stops longer than 40 minutes, so I would tend to trust it. I have done some all day shots in daylight with lith film that I rated at ISO 1. I hope that the Pinhole Assist programmer makes it possible for me to use my big cameras (longer than 200 mm, higher f number than 400). I really like the app, especially that it sets a timer for the time that it computes.

dwerg85
03-30-2012, 12:06 AM
I ran some tests using the table today. I'll preface this by saying that i'm not using the paper this was designed for. Only have access to adorama paper, which i've come to understand is not the same grade as Ilford. In either case, i was shooting a scene with a lot of range, from bright sun to darkish shaded areas. I more or less consistently got an ok exposure (highlights look ok, darks are either black or really dark) with the standard time but blown out highlights and more or less properly exposed dark areas with the reciprocity adjusted time. This kind of goes against what i suspected that would happen, complete over exposure on the reciprocity time, but the over exposure on bright parts is still kind of a no-no for me. I take it pre-flashing might prove some help there? Or am i mistaken there? (i'll post the scans tomorrow. Didn't get to upload them yet)

rydolan
03-30-2012, 12:52 AM
dwerg, I also use Adorama paper (as well as the Ilford MGIV that Even did all of his tests with) and although I have not done any proper testing to determine the speed of the Adorama paper, it practice it seems to act very similarly to the Ilford Multigrade. In fact, I use them interchangeably and don't adjust exposure times for one paper to the other.

Pre-flashing won't help your blown out highlights, but it will be an invaluable tool to tame the contrast and improve shadow detail. I encourage you to search the forum for JoeVanCleave's posts on this topic. They are paper neg. gospel. :)

If you continue to shoot with multigrade paper (as opposed to graded paper), I highly recommend using a yellow filter when shooting outdoors. It filters out the some UV light that is causing your sky to blow out so quickly, and greatly improves tonal range. It also requires an increase in exposure of 2 full stops. I've tried to get away with only a stop and a half, but it doesn't seem to be enough.

Everything I have ever learned about shooting with paper negatives I learned from the posts on this forum. If you look around in the Wet Darkroom/Lab section, you will find a remarkable wealth of information on this topic.

p.s. thanks for the plist

dwerg85
03-30-2012, 10:15 AM
I actually build provisions for mounting multigrade filters in my new 8x10 camera. I just haven't used it yet exactly because of those two extra stops it puts on my exposure times.

About those highlights. I wasn't talking about the sky. Any bright parts are totally blown out with the adjusted times. Here's what i mean. (over exposure on the right one is because i forgot to adjust for a change of camera btw. Left is adjusted time)
http://i.imgur.com/qn7h6.jpg

banana_legs
03-31-2012, 01:15 PM
Hi dwerg,

I have only done tests with up to 7 hours (after correction added) and they were reasonable for me; the caveat is that here in the UK, it is really uncommon to get 7 hours where the light level is consistent!

For long exposures, pre-flashing is a must as without pre-flashing, you may only have 4 stops dynamic range under bright conditions and with long exposures, the reciprocity failure makes the image even more contrasty. Pre-flashing helps to stretch the contrast range out.

One of the biggest variables with multigrade paper is the colour of the light; in particular if there is a high UV or blue content, the paper is likely to overexpose as the base EI can be much higher than expected. With a yellow filter, not only is the dynamic range larger (only the softer green emulsion layer responsive), the variability in the blue content of the light is less of a problem.

Best regards,

Evan

dwerg85
04-01-2012, 11:38 PM
Hmm yeah... Here in the caribbean it's either constantly bright or will get brighter when the clouds move away.
I guess that might have a more harsh impact on the exposure. I'll have to try with the MG filter. See how that works.

benjamin_wooten
04-15-2012, 01:26 PM
The blog author indicated in a post that he staunchly maintains there is no reciprocity calculation needed for exposures under 30 minutes on MGRC paper. Are people finding that is, indeed, the case?

dwerg85
04-20-2012, 10:19 AM
I'm pretty sure there are people way more experienced than me on here that can explain to you how wrong i am, but i've found that i can live without it usually. And above 15 minutes metered time the compensated times get increasingly undoable (for me) too.

earlj
05-02-2012, 06:15 PM
The newest version has eliminated all of the shortcomings that I found when I first downloaded it. I find this to be a full-featured pinhole exposure calculator. New additions include 1/3 stop ISO ratings for film, so you can up or down grade a film from its advertised speed. Apertures have also been greatly increased, up to f2048, plenty enough for my big cameras. A nice touch is that f295 is included in the aperture list, as well as f300. I think that this is a nod to the good work happening on this site. The timer can be overridden, allowing you to increase or decrease the time calculated based on aperture, film, light, and reciprocity curve. The exposure calculation includes a scale for increases or decreases of plus or minus two stops, in half stop increments.

This is a complete application, and I don't think that you need anything else. Of course, it helps if you have enough experience to know what it all means.

benjamin_wooten
05-03-2012, 08:16 PM
...don't need anything but an iPhone :)