Kodak's ECN-2 chemicals premixedA Feasibility Study: Is it worth your time to process that film?


This is a theoretical analysis of the chemical costs involved in processing color negative motion picture film, to see how worth our time it is to develop 30,000 feet of ECN-2 color negative 35mm film (something a low budget feature might consider). The techniques here can be just easily applied to any other process, such as color reversal.

This feasibility study is not conducted professionally, I have done this simply as a way to explore if it was possible to process  a large amount of motion picture film with a rack and tank style processing device and compete with lab rates for negative processing, which usually do not go below $0.13/ft 35mm.

This process is NOT the standard ECN-2 process, it uses an untested combination of premixed Kodak C-41 Flexicolor chemistry  and Kodak ECN-2 chemistry, due to the difficulty of finding and mixing all of the elements necessary for the developer, fixer, and stabilizer/final wash.

Replenishment rates in this study have been rounded up purposely, as this is an untested process and assumes a worse case scenario with solution areation in a rack and tank or spiral reel processor. Rewind and "reel and trough"/"rotary tube" style processors should NOT rely on these rates.

The cost of processing equipment is not included. The cost of "starter solutions" are also left out, as this relies on the capacity of each processing tank. For low capacities of about 5 gallons, the cost is under $100.00. The cost of water is also not calculated as this varies from locale to locale.

It's my personal opinion that the figure on the bottom most accurately represents all costs (sans processing equipment).


I. Replenisher schedules

We begin the feasibility study by determining how much replenisher will be required for processing 30,000 feet of 35mm film (which is about 5 and a half hours of film footage, enough for a very low ratio feature film). If we were to use the solutions on a "use once and dump" basis, the economics would be much worse. Replenishment (adding a special formula which rejuvinates the processing chemicals) is much more desireable from an economic perspective, even though it does require some more attention. See Kodak's processing manuals for more information on how to replenish (it can be done without expensive densitometer equipment, although this is less accurate).

Kodak does make ECN-2 chemistry premixed, but this is not easily available, it usually requires establishing an account.

To mix the chemicals from bulk (according to their formula) is not easy, because some chemicals are not available through Photographer's Formulary (like Eastman Anti-Fog No. 9) and I do not know their "real name" or where to find them. Furthermore, it is difficult to mix complex formulas such as developers, because they require many ingredients and this means ordering lots of different chemicals in various quantities.

So, opting for availability, I have decided to take an educated guess. Process C-41 for color negative still film is similar to ECN-2 in most ways, excepting the prebath, the removal of the rem-jet backing, and the bleach, which according to Kodak and several internet processing experts has a different enough formulation to create a noticeable difference on the image.

I have therefore decided to use the following modified process for this feasibility study, which combines process ECN-2 with C-41:



Solution tempurature in Degrees F

Prebath PB-2 (ECN-2)

10 seconds

80 - 90

Rinse & Backing removal

Depends on equipment

80 - 100

Kodak Flexicolor Developer

LORR (C-41)

Depends on testing, 3 min 15 sec is a starting point

100 +/- ¼ degree

Stop bath SB-14* (ECN-2)

30 seconds


Water Wash

30 seconds


Ferricyanide Bleach SR-29 (ECN-2)**

3 minutes

100 +/- 2 degrees

Water Wash

1 minute


Kodak Flexicolor Fixer  (C-41)

6 minutes, 30 seconds

75 - 105


3 minutes, 15 seconds

75 - 105

Kodak Final Wash (C-41)

1 minute, 30 seconds

75 - 105


As needed

75 - 105

* the stop bath is included in order to not place the burden of stopping development on the bleach. The stop bath is much less expensive to replenish than the bleach.

** some have reported that the premixed Kodak bleach used for process E-6 is close enough to SR-29 to be used interchangeably.

Total process time is 20 minutes, minus film loading and manual rem-jet removal. Remember, this is an UNTESTED process, only hypothesized based on data gathered from others. Be sure to read this posting by Martin Baumgarten for more info.

Now we put together a replenisher schedule, which is somewhat high-balled since we haven't tested this process yet:

Replenisher Solution

Per 100ft 35mm

For 30,000 ft 35mm

Prebath PB-2R (ECN-2)

Approx ½ Liter


Kodak Flexicolor Developer

LORR (C-41)

Approx ¾ Liter

225 L

Stop bath SB-14 (ECN-2)

Approx ¾ Liter


Ferricyanide Bleach SR-29R (ECN-2)

Approx ¼ Liter

75 L

Kodak Flexicolor Fixer  (C-41)

Approx  1½ Liter

450 L

Kodak Flexicolor Final Wash (C-41)

Approx 1 ½ Liter


Water washes

Approx 6.5 Liters

1950 L (approx 450 gallons)

Now that we have that figured out, we can go ahead and see how much juice we need for our 30,000 foot batch of film. Raw chemical prices are based on the Photographer's Formulary, plus shipping charges, others are based on minilab chemical outlets:

II. Chemical Consumption:

PB-2R Prebath Replenisher

Borax (Deca)

20g X 150 L = 3 kg = $30.00

Sodium Sulfate (Anhyrous)

100g X 150 L = 1.5 kg = $7.00

Sodium Hydroxide

1.5g X 150L = 225 g = $24.00

Kodak Flexicolor Developer Replenisher LORR

6 X 40 Liters (@$100) = $600.00

SB-14 Stop Bath (tank and replenisher)

Sulfuric Acid (concentrated)

10mL X 225 L = 2.25 L = $30.00

SR-29R Bleach Replenisher:

Sodium Bromide

35g X 75 L = 2.625 kg = $240.00

Potassium Ferricyanide

 55g X 75 L = 4.125 kg = $100.00

Kodak Flexicolor Fixer III Replenisher

12 X 40 Liters = $420.00

Kodak Flexicolor Final Rinse & Replenisher

6 X 80 Liters = $360.00

III. The Math

Now we add up all of our figures and we find that our total cost to develop 30,000 ft of 35mm film is approximately $1811.00

We work that out to the cost per foot, which is $0.06/ft 35mm film (16mm equivalent is $0.03/ft, Super 8 $0.015/ft).

As you can see, the study shows that our per foot rate is competitive with commercial laboratories. The real cost may actually be lower, but it is hard to determine without a more thorough study and further experimentation with this hypothetical process. The cost savings particularly kicks in with 16mm and Super 8 film, which often cost more to develop due to lower volume.


For those who wish to do a feasibility study using strictly ECN-2 chemistry, I have included some data below to make life easier. All you have to do is to go the Photographer's Formulary (www.photoformulary.com) or other bulk outfit and look up the cost per unit of chemical, and do the calculations.

Replenisher schedule for premixed ECN-2 chemistry:


Per 100 ft 35mm

For 30,000 ft 35mm

Prebath PB-2R

Approx ½ Liter


Developer SD-49R

Approx 1 Liter

300 L

Stop bath SB-14R

Approx ¾ Liter


Ferricyanide Bleach SR-29R

Approx ¼ Liter

75 L

Fixer F34a-R

Approx ¾ Liter

250 L

Stabilizer S-15R

Approx ½ Liter

150 L

Water washes

Approx 6.5 Liters

1950 L (approx 450 gallons)


Sodium Sulfite

2.5g X 300L Developer

22 g X 250 L Fixer

Total 6.25Kg

Kodak Anti Calcium No. 4

2.7mL X 300 L Developer

Total 810 mL  

Eastman Anti-Fog No. 9

0.3g X 300 L Developer

Total 90g

Sodium Bromide (Anhydrous)

0.8g X 300 L Developer

35g X 75 L Bleach

Total 2.865 Kg

Sodium Bicarbonate

0.6g X 300 L Developer

Total 180g

Kodak CD-3

5.5g X 300 L Developer

Total 1.65 Kg

Borax (Deca)

20g X 150 L Prebath

Total 3 Kg

Sodium Sulfate (Anhyrous)

100g X 150 L Prebath

Total 1.5 Kg

Sodium Hydroxide

1.5g X 150L Prebath

Total 225 g

Sulfuric Acid (concentrated)

10mL X 225 L Stop Bath

Total 2.25 L

Potassium Ferricyanide

55g X 75 L Bleach

Total 4.125 Kg

Kodak Anti-Calcium #4

2.8mL X 225L Fixer

Total 630 mL

Ammonium Thiosulfate Solution 58%

200mL X 225 L Fixer

Total 45 L

Sodium Bisulfite

4g X 225 L Fixer

Total 900 g

Note: No stabilizer is included in this calculation, it is best to use the premixed Kodak Stabilizer formula, ECN-2, or try one of the C-41 Final Wash formulae.

May 26th, 2002, The Movie Processing Page http://www.oocities.com/gselinsky