In the world of home film development, black and white dominates the market. This comes much to the chagrin of many amateur photographers looking to tinker and professional photographers looking to save a little money by developing colour film at home.

Resources for color film development (C-41 for negative film and E-6 for slide film) are fewer and farther between in comparison to black and white, and there is one major limiting factor – temperature. Temperature scares off a lot of people interested in trying color film development, as many development kits call for very specific and constant temperatures generally far above average room temperature (104°F/40°C) with a variance of less than two degrees Fahrenheit in either direction.

In recent years, the resurgence of analog photography in the mainstream photographic world has led to several retail products and community solutions to help with this problem, including the use of sous vide machines to create a consistent water bath temperature and modifying aquarium heaters to heat chemistry and the development tank.

There is however one solution which has fallen to the wayside: ignoring the high-temperature requirement and developing the film at room temperature instead. The test you see below were performed by me for a recent class on color darkroom printing (RA-4).

Let’s start with a few questions…

Questions, questions…

I started with two: “what makes the temperature in the C-41 colour negative film development process so critical, aside from altering the development time?” and “do negatives developed at room temperature look significantly different than those processed at suggested temperatures, especially in the age of film scanning?”

Why is temperature so critical?

According to Wikipedia (trust me, I also hate using Wikipedia as a source…), issues with temperature can cause a range of issues, from changes in development amount (either over or under) to color shifts.

Other than this Wikipedia article, information on the relationship between temperature and processing is tough to come by aside from anecdotal evidence, presumably because chemical information and processing data is proprietary and tends to be a closely held secret.

After seeing this lack of data, I decided to create my own tests and collect data based on the differences between identical negatives processed at 104°F/40°C and negatives processed at room temperature (in this case, 65°F/18°C).

To do this, I brought my Linhof Technikardan 45 view camera and Nikkor 150mm f/5.6 into the studio at my university to create two sets of negatives, both shot on 4×5 Kodak Ektar 100 film.

Test methodology

The first test set would be of a strong contrast lighting scenario, to allow an analysis of color shifts in both the highlights and shadows of images processed in room temperature chemistry.

The second set would be of an X-Rite ColorChecker Passport, which I would use to analyze overall color shifts and contrast based on the grayscale on the color target. For those who don’t know, this The ColorChecker Passport is a plastic card with carefully calibrated color swatches and grayscales.

I did not end up using the first test in my analysis, as the ColorChecker Passport ended up being a more accurate gauge of these issues. That said, I have included the results of both below.

I processed one set of negatives at 104°F/40°C for 3.75 minutes and the other set at room temperature (65°F/18°C) for 25 minutes in the Arista C-41 kit. I used a Jobo and 4×5 expert drum with constant agitation for both sets, although this is not necessary for the room temperature batch, and I simply used it because I had it available and it made 25 minutes of constant agitation less agonizingly boring.

When analyzing the negatives, I found that it was best to create composites comparing the same image side by side. All of the negatives were scanned with the same settings on an Epson V800 scanner, with no processing being done to the scans after the fact.

C-41: room temperature vs 104°F

When looking at color cast, and the rendering differences between the room temperature and 104°F processed negatives, I noted a strong magenta color cast and significantly darker image on the room temperature negatives (below left).

This is especially true in the background of the image, which is a neutral gray in the properly processed image but has a magenta tint in the room temperature negatives.

You can view the image pairs in fullscreen by clicking/tapping on the images below.

Room Temp C-41 – Comparison

65F/18C

Room Temp C-41 – Comparison

104F/40C

I also noticed this cast in the skin tones, which appear much pinker in the room temperature negative. The room temperature negative also appears to have decreased saturation in the cool tones of the image, as can be seen particularly in the headband and the blue squares in the shirt.

This stands in contrast to the warmer tones of the image, which don’t show significantly decreased saturation.

C-41: room temperature and 104°F consistency

To test the consistency of the room temperature process, I took two identical negatives, and processed them at room temperature. When the two-room temperature negatives are compared, there are noted differences between the two, the severity of which is especially evident when compared with two identical and properly processed negatives.

This is another issue that is often suggested as a reason that C-41 chemistry should be used at 104°F or the kit’s suggested temperature, if not 104°F.

Room Temp C-41 – Consistency

65F/18C #01

Room Temp C-41 – Consistency

65F/18C #02

And for completeness, two identically exposed sheets developed at 104°F follow below.

Room Temp C-41 – Consistency

104F/40C #01

Room Temp C-41 – Consistency

104F/40C #02

In the room temperature negatives, there is an evident color cast in the neutral background that, while not noticeable in the skin tones and colors, is notable when looking at a neutral surface.

This is definitely something to consider if you decide to process C-41 at room temperature, but unless I had a need to processing truly identical negatives, I would not be very concerned about in the long run, as it is minor enough to appear as a difference between two images instead of a difference in processing.

Comparing the ColorChecker Passport

I also wanted to consider the contrast of the negatives, which has also been proposed as a reason to process at the recommended temperature. To do this, I looked at only the ColorChecker Passport in both color and black and white (digitally converted of course) compared with the other.

Room Temp C-41

ColorChecker Passport (Color)

Room Temp C-41

ColorChecker Passport (B+W)

Visually, it appears that the room temperature negatives have a higher contrast than the properly processed negatives, however, a specific analysis with Photoshop does not confirm this.

When reading the grayscale output values of the grayscale on the ColorChecker Passport, they both have a range of 90%, with the room temperature negatives reading from 6% to 96% and the 104°F negatives read from 0% to 90%. This surprised me, as the negatives (below) look significantly different, but evidently, when processed, this contrast difference is negligible.

Final thoughts

Based on these analyses, I would say that while there is an obvious color shift at room temperature, many of the traditional issues proposed with processing color film at room temperature are not nearly as severe as many believe. This is especially true in the digital age, where scanning and post-production can correct many of these issues.

While I did these tests initially for a colour darkroom printing class, in reality, most people these days are scanning and printing their color film images digitally and because of this, color shifts, decreased perceived contrast, and inconsistency between negatives is much simpler to correct.

Room Temp C-41 – Negative Comparison

65F/18C

Room Temp C-41 – Negative Comparison

104F/40C

The takeaway is simple: color negative film shows some notable changes when processed at room temperature but that is to be expected from a chemical process which is intended for a different temperature and speed.

Despite this, I am glad that I experimented with processing the color film at room temperature, as it is certainly easier to perform and requires less equipment, including not requiring a Jobo or similar way to maintain constant temperature, which can be expensive to purchase and maintain in the case of the Jobo, and less reliable in the case of some other solutions.

And so, for most, room temperature development of color negative film is a perfectly viable option when it comes to processing on a budget; but as someone lucky enough to have access to a Jobo and someone to maintain it, I’ll likely stick with the standard process of 104°F/40°C, at least until I lose my Jobo access.

~ Charlie