Digibase C-41 – Batch 23

Did another C-41 development this morning, all went great and I had my mind with me this morning. I had one Ektar roll and a Reala which I developed. The Ektar roll sat in my HolgAgon which i brung with me friday morning and captured a cold sunraise. The Reala roll sat in my Hassy.

This time I was sure i nicely lowered the temperature of the film, my stab was kept in room temperature and the water wash after fixer was 30 degrees and I stepped it down a bit in the last wash. Results was nice and plain film when I cut them up for scanning. Here’s a few scan from this batch.

HolgAgon 6×12 – Focusing – Part4

Calculating focus distance
Another take on the focus distance problem. I put some mind into the formula that is used to calculate focus distance of a lens using a extension tube to see if I could calculate the focusing distances for my HolgAgon. The formula for calculating the focus distance is; d = (m + 1) * (m + 1) * f / m, where m is the magnification which is calculated from the extension divided by focal length of the lens; m = e / f.

So let’s put this formula to work using my HolgAgon build, we used a helicode 12-17mm which gives us a variable extension of 0 – 5 mm. Where 0 extension is infinity and 5mm extension the minimum focusing distance of the build.

Lets start calculate the magnification of 5mm extension;

m = e / f = 5 / 90 = 0.055555556

This gives use a magnification to use in the focus distance formula;

d = (0.05555556 + 1) * (0.05555556 +1) * 90 / 0.05555556 = 1804.99985582 = 1.8m

Nice, I actually calculated the close focus distance that the orginal author of HolgAgon has measured and what I self measured in my manual tries as explained in previous post. This means that I probably could calculate the focus distances for the HolgAgon instead of shooting images with reference points measured and using trial and error to tune the focusing. My approach now is to calculate the focus distances for 6 of the total of 15 dents on the focus ring. The dents I choose are dent numbered 3, 5, 7, 9, 11 and 13 from the minimum focus distance dent on the focus ring. These are the dents I want to mark up on the focus ring.

As I mentioned there area a total of 15 dents on the scale from minimum focus distance to infinity on the helicode, the formula ed = 5/15 = 0.03333333 will gives us ed which is extension per dent movement on the focusing ring.

So I wrote up a little c program that calculates focus distance for each 15 steps on the 5mm extension scale and the following results were archived:

Dent	Extension (mm)	Focus distance (m)
0	5.000	1.81
1	4.667	1.92
2	4.333	2.05
3	4.000	2.21
4	3.667	2.39
5	3.333	2.61
6	3.000	2.88
7	2.667	3.22
8	2.333	3.65
9	2.000	4.23
10	1.667	5.04
11	1.333	6.26
12	1.000	8.28
13	0.667	12.33
14	0.333	24.48
15	0.000	infinity

Just for the sake I also dumped the calculated data into a file to feed a plot to visualize the focusing curve:

Now, I have some theoretic numbers that I will use in a verify process, eg. measure up a focus distance in real word, use matching dent on focus ring, take an image that I will pixel-peep to see if I’m in the right ballpark. I think this process is more effective then my first approach.

To be continued…

HolgAgon 6×12 – Focusing – Part3

HolgAgon Focusing
A few months later it’s time to fix the focusing of my HolgAgon. I want 2 scales on the focusing ring. The first scale for the actual focus distance and one for marking each apertures hyperfocal distance, which I think would be most suitable for this camera. The hyperfocal distance is the closest distance at a lens can be focused while keeping the details at infinity at acceptable sharpness. This is used to get as much details through whole depth of an image as possible suitable for landscapes etc.

Measuring Focus Distances
This is not a easy thing to do. The first thing I did was to mark the indication mark which I would align up with the rotating part of the helicoid. After I got the alignment marking done I marked the start and end position aligned to it. When the start and end markings was done, I added a ‘infinty’ symbol at the marking aligned when helicoid is fully retracted eg. no extension.

I tried to measure up the focus distance a couple of times before but it’s really hard. For this process I used a acute matte screen from my hasselblad camera and mounted it using a rubber band on the back of the HolgAgon at the film plane. I used the loupe from the wrist finder to identify the sharpness on the screen. To ease the process you can lock the shutter open on the lens by using the little leveler by the shutter loading mechanism. Start loading the shutter, then pull down the leveler and fire the shutter to lock it open. This process was really hard and each time I measured a point on the scale I got different readings. However one reading was 1.8 meters which matches what the original author of HolgAgon measured up so I reconsidered my approach.

I’m going to use the original authors measurements as a ballpark and shoot a few images of real world objects, keeping notes of which dent on the focusing ring was used and what distance I measured for the shoot. This way I could verify the ballpark figures and correct them in some passes if they would differ from my HolgAgon build. This needs to be continued in another blog post.

Calculating Hyperfocal Distances
I had to dig around for a while to get all stuff sorted out, so lets talk about the hyper focal formula. The formula for calculating the hyperfocal distance takes three variables, the circle of confusion c, focal length f and aperture number N. The hyperfocal distance formula; H = (f² / N * c) + f, lets get back to that after we sorted out the circle of confusion.

The circle of confusion is calculated from the diagonal length of the film plane using the modern formula; c = d / 1500. I won’t go into details about circle of confusion due to that makes me confused… For more information see Circle of confusion.

Lets begin, first I need to calculate the circle of confusion of the HolgAgon and for that I need the diagonal of the film area. This is done using Pythagorean theorem; a² + b² = c². I used the film plane size 56mm by 112mm which is the approx film size of the HolgAgon into the equation.

d = √(56² + 112²) = 125.21980674

and calculate the circle of confusion using:

c = d / 1500 =  0.083479871

Now we have the calculated circle of confusion c which we need to insert into the formula to calculate the hyperfocal distances for each aperture.
Here follows a table of calculated hyperfocal distance for apertures f/8 – f/32:

f/32 H = (90² / (32 * c)) + 90 = 3122 = 3.1m
f/22 H = (90² / (22 * c)) + 90 = 4500 = 4.5m
f/16 H = (90² / (16 * c)) + 90 = 6153 = 6.1m
f/11 H = (90² / (11 * c)) + 90 = 8910 = 8.9m
f/8 H = (90² / (11 * c)) + 90 = 12218 = 12.2m

Acceptable sharpness is archived from half of the calculated hyperfocal distance to infinity. This means that using F/16 on my HolgAgon I can get acceptable sharpness from about 3 meters to infinity. These calculated hyperfocal distances is what I want to mark up on the focusing scale but I can’t do that now as i don’t have a correct focusing scale to referee to. This is to be done.

I’m kind of tired and might got things wrongs on this topic, let me know if you identify any oddities!

4×5 Scanner project – The birth of a project

I made a really bad decision when I bought my scanner to scan my negatives. I went for the cheap alternative which has a restriction that it only will scan medium format film (6×6). The scanner of choice at the time was Epson v600. Now I stand in front of a new problem, I want to scan 4×5 and for that I need to sell and spend big bucks on another model, namely the v700. I gave it some thoughts and wondered if I could use my v600 for scanning a 4×5 negative and it all turns into a birth of this project.

My goal is to find a way to scan a full A4 area as negative using my v600 spending less money than buying a new scanner for the job.

The idea is to create some kind of light box which will have an A4 sized surface evenly lit that is placed on the scanner. To use this light source instead of the built in light in the lid which is restricted to medium format. I have looked into several ways to do this, CCFL, LED, LED panels etc. But to keep this project on budget I will go with a normal led strip. The led should be place into a matrix on a surface with same distance between each other. To get an evenly lit surface out of it I need some kind of diffuser placed on a distance from the leds based on their light spread radius and distance to each others. I will post more information and details about this light box in future blog after is solved following problem.

The scanner will signal an error if lid is open. This only happens if negative scan mode is selected which is the mode I must go with to turn of the lights from the scanner head used for reflective scan. I looked around for a mechanical switch used to detect if the lid was closed but didn’t find any. But I did discovered that for each scan I started, the light in the lid turned on, went forward to meet up with the scanner head and started to blink. That’s it, the lid is talking to the scanner to indicate it set to go. I logged the sequence of the lid lights and tried to reproduce it with a flash light but failed. It probably needs to be in sync with a clock. Looking into the lid and the light head it seems that there are just two cables that controls the light, I assume I could jack into those cables but I’m not to fond of the idea to do harm to my scanner so maybe, I just should have a photo diode that registers and replicate the light signal from the open lid into the light box…

Anyway, the conclusion are that it seems the the hardware in the scanner is signaling through the lid light to detect if lid is closed, I need to copy this behaviour.

This leaves me with two things to investigate; Explore the little lid placed at the cable connection between lid and scanner to see if I easily could jack into the light control signal into my lightbox without to much harm on the scanner itself. Investigate if it’s possible to use a photo diode to control the box. I would prefer the latter approach due to no physical modifications on the scanner itself.

To be continued…

Digibase C-41 – Batch 22

So last night I made another batch of C-41, this time I really fooled and failed on the cool down of the film before dry and that my friends… is disastrous. It didn’t look bad when I hung em up for cutting them down, but as soon as I removed the first clamp i saw something that wasn’t correct. The film started to bow over the short edge, almost into a circle. As we all know we want them as plane as possible. I had a really hard time to cut the two rolls up, I thought if I put them into my sleeves and putted some pressure onto it over night it would sort it out. It did, some what, they are now plain on that plane but have some waves along the long side.

So lesson learned, do NOT chock the film with temperature. My mistake was that I went with a too hot stab, 38.5C and a final rinse in 30C tap water for a short period which was not enough to cool down the film base.

Next time I’ll do as previous batch, keep stab at room temperature and use the water wash before stab to cool down the film halfway to room temperature.

So here is some scan from the two rolls of Fuji Reala that was taken with my Hassy. I’m pretty happy with the results despite the messup…

Digibase C-41 – Batch 21 – Follow-up

I had some problems in the previous batch with a strong blue color cast. This seems not to be related to the actual development but with the post processing. I use darktable and its invert tool which subtracts the film base color from the image. The film base is picked with a spot which isn’t optimal and I have changed its behavior to use a area selection instead (commited upstream). Now the images were much easier to work with and here follows updated exports of images for this batch.

Digibase C-41 – Batch 21

I failed to mentioned in my last post why I pulled down the temperature for the wash and stabalizer. The reason behind that is to get the film temperature down to room temp to prevent the maniac bow I got on the film when they hang to dry. I worked out very well in my second batch.

So back to this batch, everything went as smooth as previous run, poured up my water bath at 39C degrees tap water, preheated the working chemicals in the sink with boiled water. I reach 38.5C degrees within 5 minutes so its not that big of a deal. I used the same development time table I produced for my second run.

The scanned negatives felt hard to work with, something went wrong but I don’t really know why, there is some blue cast in shadows… Can be that the film is old, more then 8 months in a closet or is the chems old ? I need to investigate this.

This batch was with 2 rolls of reala 100 taken with Hasselblad 501CM + 80mm CFE, scans processed using darktable:

Digibase C-41 – Batch 20

Previous developed batch

My first development using Digibase C-41 was really sloppy. I spent some time last night to read up and a lot of questions was raised. Digibase have left out the washing steps in the instructions, did this contaminate my liquids. Are the fill / drain times included in the development times or not, how should i compensate for the lesser time of agitation.

The strong magenta cast on the negatives indicates that the batch was overdeveloped, this means a combination of to hot solutions, too long time in color developer and too hard agitation. I needed to get the timeline for the development process settled.

• My fill/drain times are about 30 seconds and its is included in the specified development times, it does not extend the time frame. Color Developer continues to develop until the bleach is filled.

• Bleach residues leaked over to fixer is not a problem, it wouldn’t degrade fixer capabilities and there for no wash is planned in between fixer and bleacher. It’s already contaminated, maybe I will add a rinse between fixer and bleacher in future when I mix a new set of working solutions.

• Bleach time can be extended, you really can’t over bleach. So I might extend bleach time to compensate for the 1 inversion see next point.

• I might add additional inversion at 4:15 and 7:30 to compensate for the loss of one inversion due to the long fill/drain times.

Development process

For this round I picker 2 rolls which I knew came from my Hasselblad from my backlog.
I started to measured the temperature drop over time in my water bath. I measured about 1C degrees drop per 10 minutes. I measured up tap water on 39.5C and filled my bath, during this time I also boiled some water and placed my working solutions in another bath to heat them up quicker. Measuring the working solutions to 38 and moved them over to the water bath. This took about 5-10 minutes. Following the time line process I had no misses during the process, everything went smooth. No messing with different times on the timer, just started it once and let it run. I also made sure that I removed the lid of next solution when resting so it was all prepared for fill when time was in.

I followed the time line process which you will find in the end of this post. Negs came out very nicely and it looked a lot better then my first C-41 batch. When I scanned them I was amazed how this batch ended up, no strange color shifts at all, just needed to set temperature, pull down red channel a tad and fix the exposure.

My DigiBase C-41 Development process

1. Presoak – 2 min 30 secs	0:00	Fill Presoak
Controlled temp of 38C through process to step 5	0:30	Continuous agitation
	0:45	Tap and rest in bath
	1:15	Inverse, tap and rest in bath
	1:45	Inverse, tap and rest in bath
	2:00	Drain Presoak
2. Color Developer – 3 min 15 secs	2:30	Fill Color Developer
	3:00	Continuous agitation
	3:15	Tap and rest in bath
	3:45	Inverse, tap and rest in bath
	4:15	Inverse, tap and rest in bath
	4:45	Inverse, tap and rest in bath
	5:15	Drain Color Developer
3. Bleach – 3 min	5:45	Fill Bleach
	6:15	Continuous agitation
	6:30	Tap and rest in bath
	7:00	Inverse, tap and rest in bath
	7:30	Inverse, tap and rest in bath
	8:00	Inverse, tap and rest in bath
	8:15	Drain Bleach
4. Fixer – 4 min 30 secs	8:45	Fill Fixer
	9:15	Inverse, tap and rest in bath
	9:45	Inverse, tap and rest in bath
	10:15	Inverse, tap and rest in bath
	10:45	Inverse, tap and rest in bath
	11:15	Inverse, tap and rest in bath
	11:45	Inverse, tap and rest in bath
	12:15	Inverse, tap and rest in bath
	12:45	Drain Fixer
5. Wash – 2 min	13:15	Fill Water
	13:45	Invers 3 times and drain
	14:15	Fill water
	14:45	Invers 3 times and drain
6. Stabilizer – 1 min	15:15	Fill Stabilizer
Tempered halfway between room and working temperature.	…	Dip up & down with some rest in between
	16:15	Drain Stabilizer

Digibase C-41 – Batch 19

Last night I thought I was going to do my first C-41 development, but all time went into mixing the chemicals. Fortunately this evening, I got some time to plan and perform my first C-41 batch.

I choosed 2 rolls of Fujicolor Reala 100 for this batch, these rolls was taken with the HolgAgon camera on my vacation in Greece. I expected to see beautiful blue skies and deep blue water…

First off, I had to decide to settle on a temperature. Looking through the datasheet for Digibase C41 kit the working temperature ranged from 25-40C degrees. And the nominator would be the color dev with a working temperature with 37.8 +- 0.3C so I settled on 38C degrees.

With 38C working solutions I could read out the following times from the Digibase specs and this was the times I used for the development:

2 min Presoak, inversion continuously under 15 secs, one inversion every 30 secs
3 min, 15 secs Color Dev, inversion continuously under 15 secs, one inversion every 30 secs
3 min Bleach, inversion continuously under 15 secs, one inversion every 30 secs
4 min, 20 secs Fixer, one inversion every 30 secs
1 min Stabilizer, one inversion every 30 secs

Now comes the problem, how would I get my chemicals and 1 litre of presoak to the working temperature. I made a few test and gave up.  Just took the loong road found a plastic container with a decent size, measured up 50C tap water and filled the container with the liquids in place. Now, liquids in room temerature (23.5C) took about 30 minutes to get up to 40C and during that time I used a electric kettle to boil some water I used to compensate for the loss in the container water over time.

During this time I took two science fictional measures of the temperature, after 12 minutes the liquids have raised to 32.5C and container water lowered to 43.5. After 28 minutes the liquids was 37C and the container water 41C… This says nothing but I got it pretty spot on evning out the liquids to 40C

When I started the development procedure both liquids was about 40C. I heard some were that it would drop about 2 degrees while pouring (just took it for the word). Filling my dev tank takes 30 seconds. So I think I was all good with this. Next time however i will user 60C degrees tap water in the container to shorten the prep times…

Now it was time to start the procedure, all went messy and I was not on spot of the timings I used, mostly but 5-10 secs off sometimes during the process. Anyway it felt pretty good but I can definitely trim the approach. It got messy due this was the first time my tank + lid leaked and while doing the 15 secs inversion some of the chem was outside of the tank…

Anyway, I finished up and hang the negatives on dry… And the film curled up like nothing I seen before so they got cut up and under a press to see if that will flatten them out to something scan-able. The negative film base looks pretty dark but i can’t really tell, the scan will tell the truth for this batch. But I definitely have some images on the rolls.

Ok, I made a few test scans and is pretty happy with the result, however it took alot of tweaking in post. Colors are way off, especially the red channel. Also it doesn’t seem to be a linear problem. I’m tired so this is what you get!

After some readup on the magenta/red color shift/cast, it seems to origin from over development of the film.

Digibase C-41 Kit

So, as I earlier have posted, I have ordered a C-41 Dev kit to test out some color development. I went for the Digibase C-41 maxi kit because i have more than 30 rolls unprocessed color rolls laying around…

This evening I spent time to mix my first batch of chemicals up. I decided to make a 1 liter of each liquid, color dev, bleach stabilizer and fixer. I went for 1 litere because my stainless steel tank takes 4 x 120 rolls and 1 liter is enough for doing 3 rolls at the same time. 1 liter is also a good volume to handle in your kitchen.

The Digibase kit includes chemicals for color developer, bleach, fixer and stabilizer. The color developer is mixed up by four components and water, the rest of the chemicals are just a mix of one component and water. I also ordered four Jobo 1 liter containers to store the chemicals in and a decent thermometer with a good scale.

Color Developer
For 1 liter color developer you will mix 100ml of each part A,B,C and 10ml starter with 690ml water. With this maxi kit I will get 5 litre of color developer which is enough for about 100 rolls. The mix of the color developer should be done into 49C degrees tempered water and adding the chemicals in following order: part A, B, C and then the starter.

Bleacher
For 1 liter bleacher you will mix 280ml bleach 780ml water. This kit comes with 980ml bleach which will give me 3 liter of bleacher which can be used for approx 80 rolls.
Mix the bleacher chem into 40C degrees water.

Fixer
For 1 liter fix you will mix 200ml fixer with 800ml water. The kit comes with 700ml fixer which will give me 3 liter fixer which can be used for approx 80 rolls. Mix the fixer into 40C water.

Stabalizer
For 1 liter stab you will mix 100ml stabalizer with 900ml water. The kit comes with 150ml which will only give me 1 liter stabalize which can be used for approx 60 rolls. Mix stabalizer into 40C degrees water.

As you now can see I will only be able to process 60 rolls on one mix, so I need to buy more of the stab, fixer and bleacher to get 100 rolls out of this when using 1 liter mixes. When I was mixing the chemicals I wrote down on each bottle how much there is left so I easily know when i need to order more chemicals. A stabalizer is already on my list due to I need 100ml and i have only 50 left.

And here is the result of the evenings chem mixing contest:

Now, with this result I’m fit for planning my first color development batch!