Pinhole questions

[shannon_kolvitz]

I plan on making a pinhole camera and I would like to expose correctly. Does anyone know the best way to

figure out exposure with pinholes? There is a place on the internet where I can get laser cut pinholes. I

was trying to figure out the f/stop and go that route. I know that f/=focal length/aperture diameter but

how do you figure out focal length for a pinhole. Help?

[petemillis]

I wouldn't bother with a laser cut pinhole - just use a pin!

 

Focal length for a pinhole camera is simply the distance from the pinhole to the film/sensor plane.

 

The f-stop is the focal length divided by the diameter of the pinhole. But because you need a very high f-stop to get a sharp image (probably something like f100 (i.e. very small hole in relation to focal length) the the exposure time needs to be long.

 

Are you thinking film or digital? If digital then you can play around a lot to work out suitable exposure times.

 

Useful info... http://en.wikipedia.org/wiki/Pinhole_camera

[Charles_Webster]

If you are building your own pinhole camera, make the focal length shorter than the diagonal of the image i.e., make it wide angle. So for 35mm film, a focal distance less than ~40mm. For 126 instamatic film, we always used 1"

 

Pinholes are fun. To avoid extremely long exposure times, choose fast film.

 

Please post your results.

 

<Chas>

[tibz]

yes-heres how to make one-take a coffee can, a pin, some black paint, and a piece of tape. Paint the can and lid black, poke a hole, cover it with tape, load it with a 5x7 sheet of paper. Try metering, exposing for a time, and compensate till you get it right. Your pin may be slightly smaller than mine.

[tibz]

You can get some ridiculously wide shots, it's very cool.

[shannon_kolvitz]

I've used a quaker oats can and just guessed but I'm trying to make a good one this time. I'm

trying to make a panoramic 6x17

[alex_lofquist]

I've got pinholes in some of my shutters. It's too bad that I can't send them to you!

[fourthst]

Type in Jon Grepstad in your favorite browser. Read what he has to offer. It could make your

hair hurt. You can skip all that and scroll to the bottom of his page for links that will help.

You might also try MrPinhole. Don't forget Worldwide Pinhole Photography Day! April 27th.

[albert_richardson1]

Look at the PN Alternative Camera forum. There is also good information tucked away in the Large Format forum. One post I found by looking for 'optimum pinhole' credited "View Camera Basics" by Leslie Stroebel with the formula Optimum pinhold diameter (in inches) = SQRT(Focal Length)/141 and (in MM) SQRT(Focal Length)/28.

 

I made an Excel spreadsheet to calculate f-stop values based on the area of the circle used to derive them. It's not necessary for you to do this because it turns out that a shortcut to finding f-numbers that are "off the chart" is to take the SQRT of the nearest power of 2.

 

Computer people are used to the progression of the powers of 2. For the rest of us, they are 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072. These numbers produce values that fall in line with the photographically useful sequence that follows the idea of 'reciprocity.' More about this in a few lines.

 

You will drill or punch a hole to be your lens and when you're done and the hole is clean with no burrs you will be able to measure it's diameter. As you said yourself you will be able to calculate an f-stop value of yur own for it, but the problem is that to get exposure, you have to relate the hole to some known f-stop for cameras.

 

Perhaps it makes more sense to switch to an actual example. I have a Quaker Oats box approx 9" long. The focal length is 9" and the calculated optimal aperture is .021". 1/64" is .015" and 1/32" is .031" so the hole I want is roughly halfway between them. A drill bit 3/128" or .023" would be great if I could find one. This starts a search of hardware stores, machine shops, & etc. The same size in metric is .584mm, so a .6mm drill bit would be a pretty good match. Might be easier to find. I wouldn't get too hot and bothered about demanding precision here. Better to make practical adjustments than to go without making any pictures!

 

Now Exposure. SQRT(131072) is 362.03... (An f-stop for cameras) Dividing this number into the focal length 9" gives .0248". This is the diameter of the aperture for f/362. It is a really good fit for our actual aperture which is .023" or slightly greater.

 

Now I would build the camera and decide what film I want to use in it.

 

Reciprocity mentioned before is the idea that film has a constant built-in sensitivity to light. If you cut the amount of light coming through the lens in half, you wuold increase the total amount of light that reaches the film by doubling the length of time to let the light in to get the same exposure as before. In our case, we can count off the number of times to double the exposure time by counting the f-stops between a known value (we haven't measured yet) and the f-stop built into the "QO Special." Adjustable cameras allow you to vary both the shutter speed and aperture size for exposure. Our camera requires us to use a stopwatch of some sort to measure time only.

 

Set the ASA of the film you're using into a light meter and take a reading, or if you don't have a light meter, use the "Sunny 16" rule to get a base exposure to count from. The Sunny 16 rule says that when you stand outdoors in the open in the middle of a sunny day, use shutter speed 1/ASA at f/16 to set the camera.

 

I decided to use Kodak TRI-X pan film ASA 320 for my new camera. It's a sunny day and I forgot my light meter. The base exposure is 1/320 sec at f/16. F/16 lets in 1/264th of the light from a wide open lens, so base the count at 256 in the sequence. My count shows that I have to double 1/320 9 times to reach f/362 for my camera. I get 1.6 sec for this.

 

Now it is necessary to adjust the exposure time for something called "reciprocity failure." Reciprocity failure is the term given to very dim or very bright conditions that go beyond the exposure sequence built into the film. It takes longer for a very dim image to build density in a negative than ordinary exposure would tell you. This will be true for TRI-X in my "QO Special." The Kodak film data sheet tells me to give an extra half stop exposure when the calculated time is 1 second. The exposure time for the next f/stop in our sequence is 3.2 seconds. Considering the difficulty of measuring time and working a hand-made shutter, I think it would be pretty good to hit 2.5 seconds.

 

Check all this stuff by talking with the guys in the pinhole forums. I hope that I'm right, but even if I'm off on a point or two, you will learn a lot figuring out the same things for yourelf.

 

Good shooting!

 

 

 

 

 

[lobalobo]

The one comment in a post above with which I disagree is "choose fast film." I prefer slow film for the simple reason that on a typical pinhole camera the shutter is controlled by hand and so if exposure is less than a few seconds it's hard to be accurate. I get great results using Efke 25 and exposures of 10 seconds in bright sunlight, up to 30 seconds on cloudy days. Of course, any movement of the subject or camera with these times will cause the image to blur, but pinholes are not well designed for moving subjects or handheld photography anyway.

[albert_richardson1]

I'm continuing my previous post to revise my remarks insofar as I have learned more about the subject as a result of having attempted to explain so much in great detail. Learning requires a person to be willing to get it right, not the first time perhaps, but eventually.

 

The topics to address are: the size of the pinhole, a readily available spreadsheet program a pinhole camera maker can download and use for free, and a chart that can be used to calculate exposure time.

 

Two factors play together in finding the theoretical optimun pinhole size. The first is the sharpness of the resulting picture, and the second is the amount of time available to the photographer before the scene changes so much it ruins the image already collected inside the camera. Light bends when it crosses a barrier of some kind such as the edge of a piece of glass or water. Optics studies the effects of bending on light (among other things) and forms the basis of the designs of the various lenses used in making cameras. There is a lot of discussion about DOF here at PN, and the principle underlying DOF is the notion that light passing through the center postion of a lens gets bent less than light at the edges and, so being bent less, more of the scene in front of the camera is in focus at the same time. More light bending that takes place inside a lens means less DOF. The usual means of controlling which part of the light gets all the way through the lens to the film plane is the aperture opening. This is the variable opening inside a lens the familiar f/stop ring or control manages. The pinhold maximizes the DOF idea by proposing a camera obscura in which light never passes through any barrier, and so focuses the near foregound as well as the far extent of the background. There is a price for maximum DOF, however. It is that to let in enough light to get an adequate exposure, the hole must be so big that the tiny parts of an image must overlap each other leading to a slightly fuzzy or soft image. The hole cannot be so big that too much light gets in because then the overlapping effect is so destructive that no image can be formed at all. The sharpest image possible in theory would have a pinhole smaller that the diameter of the receptor (called a pixel in digital devices), which in turn would be sensitive enough to capture the image in real time.

 

The amount of time available for making a picture is dependent on the scene itself. Things that move slowly enough to appear to be still for the entire exposure would produce sharper results than things in motion.

 

Another consideration is the method available to the camera builder for making the pinhole itself. I spent a lot of time explaining how to find the diameter of a theoretical optimum hole based on the idea that once the diameter is known a person could find a way to drill it. Another approach to the same thing turns the process around by beginning with a needle or a fine drill bit to make the hole before its effects on picture-making is known. I have to admit that I have now discredited the algorithm said to come from "View Camera Basics." I will describe a method for creating a chart that allows you to either drill to a known diameter or calculate the exposure needed for the diameter you happen to have made.

 

I use Microsoft Excel which is the spreadsheet component of the Microsoft Office suite of products. MS Office is widely used in business settings, but many home computer users might find it to be too expensive to be of much value. Sun Microsystems has sponsored a project to create and distribute for free an office suite alternative to Microsoft Office developed using its Java programming environment. I believe that it would be most valuable to photographers to propose a tool they can set up without buying anything very expensive, so I downloaded Openoffice.org 2.3 for myself to test the chart I am about to propose to you. I am pleased to tell you that it ran the Excel spreadsheet I call "Study for Pinhole Optimum Diameter Calculation" very easily with few changes.

 

I will describe how to make the chart and what it does in another post.

[albert_richardson1]

Now to make the "Study for Pinhole Optimum Diameter Calculation" spreadsheet. I should also tell you that this sheet calculates basic exposure as well, without allowing for reciprocity failure.

 

The first step is to download and install the spreadsheet program itself if you do not already have one. I have sucessfully tried out the two programs I already mentioned, but there are other products out there too. I am not familiar with them and if it should turn out that my instructions don't work with them, there is nothing I can do for you. You may find the product I mentioned earlier by looking for it on the Internet. It runs on Windows, Linux and the Mac providing your system meets the minimum system requirements for using it. There is no charge for using Openoffice.org 2.3, and you may freely give it to others if you wish to.

 

I want to make the point that I am not a spokesperson for the product, nor am I endorsing it, nor am I suggesting that PN might endorse it. It simply makes no sense to propose a useful approach to solving a calculation problem for pinhold photographers without providing the means for them to run it for themselves.

 

Start the spreadsheet program. It automatically opens a new workbook and shows you the first worksheet. That is, you see a grid on your screen. Each box in the grid is called a "Cell". The cells running from top to bottom are in a column and those lying next to each other across the worksheet are called a row. We will be typing in a few words of text to remember what the columns mean, and some special expressions called formulas to make the spreadsheet program do the work of performing the calculations we want for us. You will be astonished at how little we actually have to do to solve this pinhole problem!

 

There is a letter of the alphabet at the top of each column and a number to the left of every row. Starting in column 'A' row '1' type in "Power of 2". Tab or click in column 'B' and type in "Exponent". Continuing across the next three columns, type "f/stop", "Aperture" and "Exposure". You now have titles at the top of five columns. Click the number '1' to the left of column 'A' so that the entire row is highlighted then find the 'Center Text' button (It says "Align Center Horizontally" when you put the mouse cursor on it.) Click this button. Now the text looks nicer.

 

Starting in row '2' of column 'B' type in the number 0. Then on row 3 of column 'B' type in the number 1. The spreadsheet processor will fill in a sequence of numbers down the column using these two numbers as a seed when we click and drag downward across them. Here's how left click cell B2 and drag down over cell B3. The cells turn black (on my computer at least) and you will see a small box in the lower right corner of the highlighted cells. When you position the mouse pointer over this box it turns into a small cross. Do this and then drag the small cross down the column. A small message box appears that contains numbers like 2, 3, 4 etc. as you go down the column. These numbers represent the sequence that the program will put in the cells when you stop. For good measure, I went down until the number reached 30. When you stop dragging downward, you will see that column 'B' now contains a list of numbers running from 0 to 30.

 

These numbers are the exponents we will use next to calculate the powers of 2 in column 'A'. I think you will agree that by having the computer calculate these values instead of us there will be fewer mistakes and the process itself will be clearer.

 

Now click on cell A2. This column will contain a sequence of numbers that will be very long at the bottom. Right click the cell to open a menu of things we might do with respect to this cell. Look for and click 'Format Cells' on the list. A pop-up window opens up. It has tabs inside it across the top. Look for the box that says "Thousands separator" and click it. Click 'OK' to close the window. We will make the column a little wider later.

 

Now we type a formula into cell 'A2' to make the program calculate the powers of 2. You must type exactly what's shown here. Any creativity or mistakes on your part will result in frustration and failure for you. Omitting the quotes I put in to show you where to start and stop, type "=2^B2". The symbol after the 2 is an 'uppercase 6'. This expression reads: Raise the number 2 to the exponent contained in the cell next to it.

 

The next step is to copy this expression down column 'A'. The technique is the same as we used for column B, but because we're copy a formula there will be a difference in the result. For one thing, the program will automatically adjust the cell reference as it goes. It will automatically proform the calculation and show us the result.

Click cell A2. Notice the little box in the lower right corner and put the mouse pointer there. When you see the pointer turn into a cross click and drag it down the column until you get to the last exponent in column B. Column A is now full of values except for the end that contains number signs. Click the 'A' at the top of the column and then look for the word 'Format' at the top of the screen. Click Format and then Column and then choose 'Optimal Width'. Reply Yes to the message box that appears.

 

Column A contains the powers of 2 and column B contains the exponents used to calculate them. Later on we could use column B to count the steps from one setting to another to determine how many times to double shutter speeds for exposure.

 

Column C contains a value obtained by taking the square root of the powers of 2 in column A. I called this column f/stop because these are the very same values you would get if you calculated the area of the circles involved in finding the diameters of the apertures needed to find f/stops using a focal length.

 

First set the number formatting by selecting (clicking) cell C2. Right click cell C2 and choose 'Format Cells'. Click the Numbers tab inside the pop-up window and the look for and change the number of decimal places to 5. Click OK to close the window.

 

Once again you must type exactly what you see as the formula in cell C2. Omitting the quotes, type "=SQRT(A2)". Now select this cell and drag the little box down the column as with column B and column A. This time you see a progression of numbers starting with 1 and ending with 32768.00000. The trailing zeros and long decimal fractions will probably look strange at first, but what you see here is a list of f/stop values beginning with 1 which represents a wide open lens built so that the maximum aperture is the focal length itself, and carrying you through every f/stop value possible for 30 steps! The reason for posting such a thing here is that it takes you through the actual f/stop numbers for all sizes of pinhole down to the point that no exposure would be possible if you could drill a hole that small. This is the basis for testing all algorithms of the sort proposed earlier for optimum hole size, and it allows you to determine your own design based on actual measurements you make.

 

We know that the f/number is the focal length divided by the aperture, and that a photographically useful aperture divides the amount of light by a multiple of 2. It follows, then, that we can find every photographically useful aperture by dividing the focal length of any lens by the f/stop number for that opening. This is what we are going to do now.

 

Cell D2 is where we will enter the focal length of a lens, or for us, our pinhole camera. Pinhole focal length is simply the distance from the hole to the film plane. Select cell D2, right click and select Format Cells as before. This time click the 'Cell Protection' tab and then click the 'Protected' box to make the check mark go away. Click OK to close the window.

 

Now click cell D3. Open Format Cells and increase the number of decimal places to 5 to allow very small numbers to show up at the bottom of the column. Close the formatting window by clicking OK.

 

Now the formula for cell D3. We saw how copying a formula caused cell references to change relative to the cell using the formula. This time I am going to refer to a cell in a way that won't change when the formula is copied. Once again, except for the quotes, type exactly what you see: "=$D$2/C3". This expression divides the focal length located in cell D2 by the f/stop number located in the cell immediately to the left of the aperture cell. Select cell D3 and drag it down the column by its little box as before. The reason for having five decimal places is that these apertures get down into the 1/10,000 of an inch range.

 

Save the worksheet using the "Save As" menu item as for any other Windows program.

 

When you type a number in cell D2, the program automatically and immediately shows you the apertures for every f/stop for 30 steps. Using simple direct inspection you can easily see the f/stop that would apply for any pinhole you might drill or punch once you know its diameter. I have in front of me, for example, a tiny #64 drill bit having a diameter of .036". Returning to the "QO Special" I mentioned earlier with its 9" focal length, I find that .0351 hits an f/stop dead on. I can simply accept the result or switch to a #65 drill bit that is .035" for a more precise fit.

 

By running test for various focal length values in cell D2 I was able to determine that the result of dividing the SQRT of the focal length by 141 gives inconsistent results. The relationship of any focal length to the f/stop number that yields optimum results should stay the same. As the focal length increases the optimum aperture should increase as well and by a proportional amount. This algorithm does not do that.

 

The variation of the algorithm using 28 as a divisor for metric measurements is simply nonsense. You can see for yourself that although cell D2 contains the numer of units measured from something, it does not specify what scale those units should fit. The only requirement here is that the user understand that the results of calculations performed on the measurement belong to the same scale. Very simply put, calculations performed on 100mm will yield the same results as for 100" for all of the aperture values, but measured with a different ruler.

 

It has gotten very late so I will have to explain the exposure column later.

 

 

 

[albert_richardson1]

I called the last column 'exposure' earlier, but a better column title might be 'Shutter Speed' instead. This is very simple column that doubles the shutter speed you find for any f/stop for all of the smaller apertures below it. Simply enter the number 0 in cell E2. Format cell E3 with three decimal places and thousands separator. Omitting the quote, enter "=E2*2" in cell E3. Now copy this cell down the column using the little box as for the other columns.

 

When you put a number in the Shutter Speed column, the program automatically doubles it for the rest of the column. You can enter a fractional shutter speed by typing it as a formula, "=1/60", for example. The results are seconds, and require you to do your own conversion to get hours and minutes when needed. Clear the value by dragging the empty cell above your entry over it with its box.

 

You must consult the film data sheet for the film you are using to get the adjustment needed for reciprocity failure. You may have to increase exposure time as well as development time to get the results you want.

 

The first three columns are static once you get them set up. Most photographers would think that only the third column, the list of f/stops, is of any interest, mainly because there are few places to find so many listed. Besides that few people understand how to do the repetitive calculations needed to make that same thing using paper and pencil.

 

I gave a metric equivalent of a measurement in inches in my first post. This value came from a special feature built into Google to perform weights and measures conversions. Enter a special expression in the Google command line and it understands that you want to see the result of a conversion. When I enter "9in in mm", for example, it shows me "9 in = 228.6 millimeters" instead of a list of web sites. I Googled ".021in in mm" to get the value I described. If I had tried getting the same result using the "SQRT(focal length)/28" algorithm instead, I would have quickly discovered that it does not work.

[albert_richardson1]

I find now that I have to back-pedal with respect to the algorithm that divides the SQRT(focal length) by 28. The reading I did here on PN and in a collateral reference site identified ten different methods for finding an optimum pinhole size. I dare say every one of them is 1,000% better than I am at developing such a thing. SO... I did what any reasonable person would do. I added them to the spreadsheet I have been describing to you as a further aid in building your camera. They can speak for themselves directly to the calculations you want to make, and then you can decide which one you like best.

 

Add "Optimum Theory", "Optimum Result (mm)" and "Optimum Result (in)" column titles to the right of the titles already in row 1. The first column is for identifying and giving credit to the originator of the method. The next two columns are for the formulas. Some of them use factors such as the wavelenth of light in the same units of measure as the focal length. For this there are two columns. Simply choose the result that fits the scale you used.

 

The first theory belongs to "Rayleigh", so type Rayleigh in the next row below "Optimum Theory". His algorithm is 1.9 * SQRT(v * f), where v is the wavelength of light and f is the focal length of the camera, both measured in the same units. Enter "=1.9*SQRT(.00055*$D$2)" in the next cell in the row below 'Optimum Results (mm)', and "=1.9*SQRT(.0000216*$D$2)" in the next row below 'Optimum Results (in)'. The expression '$D$2' is the absolute cell reference to the cell that you put the focal length in if you haven't changed any of these instructions.

 

The next theory belongs to "Renner". His algorithm is 2*SQRT(v*c*f). Once again, v is the wavelength of light. 'c' is a constant somewhere between .5 and 1, so I arbitrarily chose .7 for it. 'f' is the focal length of the camera. Enter "2*(SQRT(.00055*.7*$D$2))" and "2*(SQRT(.0000216*.7*$D$2))" as before.

 

The next theory belongs to "Platt". His algorithm is simpler that the other two. He simply finds the square root of the focal length / 1300. Enter "=SQRT($D$2/1300)" in both results columns.

 

Then there is "Dobson". His algorithm is similar to Platt's. In fact, Dobson would be the one I would have to apologise to for the rough treatment I gave his work. Simply divide the SQRT of the focal length by 25 for either scale. Enter "=SQRT($D$2)/25" in both columns.

 

And then "Connors". Connors does not have a value for focal lengths measured in mm, so leave this column blank. His algorithm is ".0073*SQRT($D$2)".

 

The rest of the references are to books with titles and authors' names too long to put in a simple cell, so I assigned them numbers instead, and in joined cells below typed in the necessary text.

 

Going on: 1 is "Applied Photography, by Arnold, Rolls and Stewart". I put '1' in cell F7, and the rest in cell F18 I joined over to cell J18. This algorithm uses the wavelength of light, so there are two versions: "=SQRT(3.6*$D$2*.00055)" and "=SQRT(3.6*$D$2*.0000216)".

 

2 is "Seeing the Light. by Falk, Brill and Stork". Their algorithms are "=2*SQRT($D$2*.00055)" and "=2*SQRT($D$2*.0000216)".

 

3 is "Materials and Processes of Photography by Stroebel, Compton, Zakia, Current". This is the other algorithm I repeated in my earlier discussion. It is the same for either scale. It is "=SQRT($D$2)/141".

 

4 is "Ilford Manual of Photography". This algorithm is almost exactly the same as the last one. Enter "=SQRT($D$2)/125" in both columns.

 

Finally, 5 is "Handbook of Photography by Henney and Dudley (1939)" This has no entry for inches and the mm result is given with "=SQRT(.00007*$D$2)".

 

The amazing thing about all this work is that as soon as you put a focal length value in cell D2 the computer instantly updates all of the cells that reference it.

 

I added an average under each of the columns just for the fun of it. I guess my reasoning is that if they all can't be right, then perhaps an average will find some happy medium between them. This will take some serious trial and error to validate.

 

I also added a hyperlink to a standard drill bit chart showing all sizes of numbered and fractional drill bits in both U.S. and ISO measure. If you decide to drill a pinhole instead of punching one, then it makes sense to choose a drill bit as close to the size you need as possible. If you don't already have the bit you need, you will be able to buy the very one based on the chart. I called this the "Drill Size Chart" and the URL is "http://www.engineersedge.com/drill_sizes.htm" (at least until it changes).

 

I'm going to try to upload a .pdf file in place of the picture submitters are allowed to include with their replies to show you what this article describes. If it works, you will need the adobe Acrobat Reader to view it.

[jim_stewart]

My quick and dirty formula for the optimum pinhole size is diameter in inches = 0.0015 times the square root of the focal distance in mm. So if I have a 4 inch (100mm) focal distance the pinhole should be 0.0015 times the square root of 100. This is .015 inches or about 1/64 inch.

 

For the exposure take the f/stop of the pinhole camera and divide it by 16. Square the result (multiply it by itself). This is the amount you need to multiply the f/16 exposure time by to get your pinhole exposure. Using the above example we have 4 divided by 0.015 which is 267. Thus our aperture is f/267. Dividing 267 by 16 we get 16.66 and squaring that we get 277. We need to keep the shutter open for 277 times what the f/16 exposure is. If we are using 100 speed film in bright sun our exposure time is 277 times 1/100 or 2.77 seconds. If you are using a tabular grain film such as T-Max go for 3 seconds or so to account for reciprocity. If you are using a conventions film such as FP4 use 5 seconds or so.

 

Hope this helps.

 

Jim

[l.dwight_horricks]

Thats a lot of info...all of it good...and all good points of departure..but in the end the

only way to really get the results you want is by trial and error, taking detailed notes

and building a system of calibration that includes the film stock, lighting

conditions,exposure,development...without doing this you will not gain the

knowledge you need to have technical and creative control over what youre trying to

achieve...its like this with any photographic process...I shoot with a hasselblad and

a variety of pinhole bodycaps with different f/stops...I use a sekonic incident meter

to measure the scene/subject EV and have a built a table of exposures based upon

EV, lighting conditions and film stock,developer/processing...and I bracket (nice

thing about shooting with a hassy and A12 backs). However you come about your

exposure system you must (if you want consistency and control) do enough testing

and taking of detailed notes with all of your preferred materials and procedures so

that its not just hit and miss...unless of course hit and miss is what your after...at

some point exposure and reading the lighting conditions just becomes 2nd nature

and you may get to the point whereby you hardly refer to any kind of table or

formula...thats how it is with me...what isnt mentioned here (because I suppose it

wasnt asked) is Contrast and its an issue especially with pinhole...I've found in

general pinhole, and zoneplate images suffer from low contrast compared to lensed

photography...as a rule slower films are higher in contrast than faster films and I

personally prefer to work with slower (higher contrast) films such as PanF 50 and

FP4, and develop accordingly for a neg that works for me...its my personal

preference but I feel it makes for stronger images...

 

GOOD LUCK...