Accidentally shot 160iso at 125iso - do I need to pull process?

Hi all,

 

As the title explains I accidentally shot a roll of Portra 160 with my light meter and camera set at iso 125.

 

Just wondering if I should direct the photolab to adjust the processing to accommodate this (it costs a bit more for push/pull processing)... and if not will there be a big discernible difference in the exposures?

 

Thanks in advance

I haven't used Portra much, being partial to Ektra, but I would guess that the difference on a color negative film between the two ISOs in not a factor, being easily corrected in printing or scanning.

Most CN films have latitude of around 2-3 stops.

 

However, some claim its exposure is more critical for skin tones (see An Introduction to the Portra family - Carmencita Film Lab)

Ignore what you did. Just send the film out for processing. All films have "latitude". This is a tolerance for both over and under exposure. The difference between 125 ISO and 160 ISO is about 1 f-stop. An f-stop is a doubling or halving = 2X change. This is well within the film's latitude. Anyway, the best we can do when setting the camera is +/- 1/3 f-stop. The best the film maker can do to hit the end point ISO of 160 is +/- 1/3 f-stop. The best the photo lab can do to keep the activity of their developing process on specification is +/- 1/3 f-stop. These variables are accumulative. In other words all three variables can add up to 1 f-stop error if they all go in the same direction. What I am trying to say is, don't worry about your 1 f-stop error.

No, that’s only a minor overexposure and Portra has more than enough latitude. Process as normal and don’t worry about it.

The difference between 125 ISO and 160 ISO is about 1 f-stop.

It's actually 1/3 of a stop (100, 125, 160, 200).

My experiance is you can easily go a full stop over or under withiut too much issues. That's 80-320 range. Develop as normal.

In any roll of film, particularly if your metering technique is not too good, your meter is flaky, or you have challenging light conditions, it’s entirely possible that some of your exposures would be out by at least your 1/3 stop in any case. With roll film you can’t compensate for this by over or under developing (unless the whole roll, as yours, is similarly affected) but more often than not you get a very useable negative. Don’t worry about it.

It's C-41 film. It has a latitude as wide as a barn door.

Just wondering if I should direct the photolab to adjust the processing to accommodate this..

You could, but they'd probably just have a good snigger as soon as you were out of earshot.

You might find that you like it.

 

Back when I regularly shot C-41(which I haven't in a while) I would regularly overexpose it by 2/3-1 stop(i.e. 160 would be 100, 400 at 200). I found that it would often punch up the saturation nicely. Fuji "4th layer" films would also benefit from doing this in mixed lighting, and could be corrected for incandescent without a filter a bit better than shooting at box speed.

 

I'll add that I do expose Ektar 100 at box speed, but I find overexposure to be good both with consumer C-41 materials and with the classic pro low contrast, low saturation films(esp. Portar 160NC and 400NC-Portra 160 replaced both 160NC and 160VC, and is something of a middle ground in saturation and contrast between the two).

There might be interest in doing something different for underexposure, but Portra, like other C41 films, has a large latitude for overexposure.

 

The problem comes when you underexpose (wrong meter setting) on a scene with meter fooling back lighting, and where you are stretching the exposure because you don't want to handhold 1/4s.

 

https://imaging.kodakalaris.com/sites/prod/files/files/products/e4051_portra_160.pdf

 

You can see from the characteristic curves that it is pretty much straight for 3 logs (10 stops), with

only a tiny deviation near the end of the red curve.

 

Most films show the curve up to where they level off, but not this one.

 

One result of the low gamma on C41 films is that they are more sensitive to exposure when printing.

Pretty much, they require a printing exposure meter, or better, an analyzer that will compute

exposure and color filter selection.

http://www.tmax100.com/photo/pdf/kodakflexsmalltank.pdf

 

is the data sheet for process C-41.

 

There are push times for Portra 800.

 

Note that C41 times are independent of film type or speed.

 

For most black and white developers, for related films of different speeds, faster speeds

need longer times. Bigger grains take longer to develop than small grains.

 

So, one should not be surprised that a faster C41 film would have an optimal

development time longer than a slower film. The claim is that Portra 800 is designed

to push to 1600 or 3200.

Process normally it would come out near perfect. I found I have the best exposure shooting Portra 160 at EI 100.

Let’s also not forget that at one time, a whole lot of photos got taken on cameras with a single fixed aperture and shutter speed. This started back in the early days of photography with box cameras, and continued on well into the 2000s with disposables. The latter on particular set and exposure that’s probably about right for overcast outdoor conditions, let the film handle scenes brighter than that, and let the flash take care of darker scenes.

Let’s also not forget that at one time, a whole lot of photos got taken on cameras with a single fixed aperture and shutter speed. This started back in the early days of photography with box cameras, and continued on well into the 2000s with disposables. The latter on particular set and exposure that’s probably about right for overcast outdoor conditions, let the film handle scenes brighter than that, and let the flash take care of darker scenes.

 

Yes.

 

As far as I know, that is why C41 (and C22) films are they way they are.

 

They work with simpler cameras, but require fancier equipment to print.

 

There are many more photographers than print labs, so making cameras simple works.

 

This isn't so obvious for a film like Portra, expected to be used by professionals, and not

in such simple cameras, but that seems to be the way it works.

This isn't so obvious for a film like Portra, expected to be used by professionals, and not

in such simple cameras, but that seems to be the way it works.

 

Yes, the Portra is-presumably-intended to be used in cameras that have the ability to change their exposure settings, and presumably by someone with access to a meter(whether built in to the camera or an external meter). Still, though, the target market for the entire line of films-going back to the Vericolor days and probably earlier-has been people like wedding photographers where you need a lot of dynamic range for many photos. That translates well into good under/overexposure tolerance also.

 

There was one "mass market" film in the Portra line-400UC. I'm at least calling it mass market since it was available at Wal-Mart, and is quite possibly one of my favorite C-41 emulsions ever made. It's also a BIT more fussy about exposure than film like Kodak Gold, but is still quite tolerant of over-exposure.

There is no Walmart in Seattle, though there is one 14 miles away, which I don't get to very often.

 

It occurs to me that a big user of color negative film is the movie industry, and they might also like a

lot of dynamic range or exposure latitude.

 

Remind me, that I once knew of an Ektacolor film, also ISO 160, but only available outside

the US. I had some in the VPS days.

Doesn't look like the OP has been back since the day of the orig post, but since there are other comments about Portra film I'll share a little experience.

 

I spent years at an outfit that ran a couple of miles of Portra 160 NC daily. Same with its immediate predecessors - VPSIII and VPSII. We tested extensively before switching to each of these films, largely to be prepared for anything that might go wrong in our shooting/processing system, but also to decide if we WOULD switch.

 

One of the first things we'd do, aside from sensitometry, was a series of studio tests using electronic flash. We'd start out with an exposure series with human models under typical studio lighting conditions - mostly frontal lights with a moderate ratio. The exposures would vary from maybe 2 f-stops under to perhaps 5 stops over, in half-stop increments. "Normal" exposure is confirmed by densitometer readings on both flesh tones and grey card (see Kodak data sheets for details), as well as via Kodak PVAC (negative analyzer) comparisons using Kodak "printer control negatives." (Since we are also monitoring the processing via "control strips" we know that the processing is not introducing any problem with these methods.) It's pretty normal to find close agreement between both these methods as well as incident meter readings using properly calibrated meters.

 

The exposure evaluations were done by optically printing, onto the appropriate professional paper, then comparing the results visually in well-lit color evaluation booths. The way we made the prints was to first hand balance the "normal" exposure to a "best" print, pretty much agreed to by a panel. Then, every other exposure being evaluated is hand balanced to match the flesh tones to that, within 1cc of color (this is a really stringent criteria; essentially they can not be distinguished from each other, colorwise).

 

Setup details largely out of the way, here are the approximate results (I say approximate as it's been over a dozen years since I had MY nose in those works, so I'm going from a iffy recollection). First, from an exposure range of roughly 1/2 to 1 stop under, to about 3 or 4 stops over, the prints could essentially not be distinguished from each other, colorwise. (In the case of dark to very dark-complexioned subjects, the underexposure latitude mostly goes away). And somewhere beyond 4 stops over, stronger colors picked up what I would call a "creamy" sort of appearance. But this would likely not be recognized by a photographer who had not done a similar comparison (most have not, probably because it would be a costly test from a competent pro lab).

 

Some might wonder, well if I say this, how do I explain all of the photographers who find improved color when they overexpose slightly, or the wedding photographers who overexpose several stops to get a "dream-like" effect. Well, I don't really know for sure, but here's some possibilities. First, if they are not using the ideally balanced lights, such as studio flash, then it's likely that at least one of the color layers is being somewhat underexposed relative to the others. It's also possible that their exposure meters are not on the money, or that their film processing is out-of-spec (you don't know for sure without seeing their process control charts). Or their printing might not be consistent, leading one to make erroneous assumptions that the film exposure was the pertinent factor. And in the years since scanning of negs, then digitally printing, became prominent, these operations are possibilities for more unexpected variation. In order to determine these things conclusively, some controlled tests would really be needed.

 

Another question might arise, if Portra film was/is so tolerant to exposure, why didn't more amateurs use it? Well, I'd say basically several reasons. First, it was more costly. Second, in the days of optical printing, at least, if you took it to a non-pro lab you'd probably get poor results. If the lab did not specifically have a printer "channel" set up for Portra, then the results would be substandard. Unless they are hand balancing with multiple test prints (which low-priced labs can't afford to do). And to set up a channel they need the not-cheap printer setup negs on Portra. And what lab is gonna keep buying and using those if no customers bring in that film? And lastly, the pro portrait/wedding films like this have more subdued color. When people photograph colorful things, they generally like the photos to also be colorful. So an amateur who tries a pro film and gets worse results is more likely to abandon the (more expensive) pro film.

 

One might also wonder, why did so many pros use these more expensive pro films? Well a very big part of it is that the manufacturers all had professional support network operations that catered to their pro lab customers. This was far deeper than most people would imagine; you had to have been there to appreciate it.

Wow, 1cc on the print. I think the filters I have only go down to 5cc, which means 10cc on the print.

 

For those not used to counting in cc, 1cc is about 0.03 stops.

 

I started using it when I found that I liked the colors not to be overdone, and that I didn't have to worry about keeping it cold.

(I did keep unused rolls in the refrigerator, but they might stay in the camera for a month or so.)

 

For some time, I sent them to Qualex, which was somehow run by Kodak.

This was mostly for pictures of the kids when they were little, not something that needs 1cc.

 

It wasn't that much more expensive. Well, the discounts I remember were on multiple rolls

of 24 exposure Kodacolor. Pricing on 36 exposure rolls, including processing, and the difference

was pretty small for VPS. Not so long after the change to Portra, I started doing more digital,

and might not have noticed price increases. That was through retailers with enough professional

customers to keep stock moving.

 

Not so long ago, I bought one roll each of Delta 3200, TMZ, and Portra 160.

The Portra was the cheapest of the three. (Again, from a retail store.)

Wow, 1cc on the print. I think the filters I have only go down to 5cc, which means 10cc on the print.

 

The normal filter increments go to 2cc; any finer than that needs a different control system. But it also takes a tightly controlled process, etc., to do it predictably. I would guess that about every half dozen times the 1cc adjustment doesn't show up right, so you redo it. Or, for us, someone might call out a set of 1, 2, and 3cc to bracket around the desired correction.

 

As a note, I think that most people (with "normal" color vision) can see such a change, side by side, although someone might have to guide them as to what to look for. They might say, for example, "look at skin tone in the forehead; does one of these prints look a little "cooler?" (cooler means bluish). Generally the person can decide which one looks that way.

It seems that I have two sets of filters. One is for Cibachrome that goes down to 0.05, the Unicolor set to 0.025.

 

In college years, I did some Ektachrome 1993 printing, which like Cibachrome doesn't have the 2x filter effect.

 

Yes maybe side by side, but without a nearby reference, it is harder.

The difference between 125 ISO and 160 ISO is about 1 f-stop.

1/3 of an f-stop. (with due respect) The rest of Alan Marcus's post is 100% valid, including that even 1 stop overexp would be nothing to worry about.