The HP5 Plus 100 ASA Experiment: A Happy Accident?

Hello lovely people.

I’m a bloody fool. I made the stupidest of mistakes when shooting HP5 Plus 400 speed film at ISO 100.

I’d been intending to use 100 ASA film in my Nikon FE, so in preparation, I had set my camera’s ISO dial to 100. I loaded the HP5 and forgot to change this blasted setting. By the time I realised, I had already taken “some” photos. I didn’t want to wind the film on to change the setting because the sun was shining and I didn’t want to waste the light.

In for a penny, in for a pound. I thought, “What the heck?” They say you have all this “latitude” with film, so I went online to find out if I could salvage the roll. Here we go for a walk in the Parc Garenne Lemot in Clisson.

I developed the film in Ilfosol 3 (1:9) and used the development times for Kentmere 100, praying that I would have something usable…

ParameterDetails
FilmIlford HP5 Plus 400
ExposureRated at ISO 100 (2 stops overexposed)
DeveloperIlfosol 3 at 1:9
Development Time5 minutes 30 seconds (using Kentmere 100 time)
ResultLower contrast, smooth tonal transitions, fine-looking grain, excellent shadow detail
CameraNikon FE
LocationParc de la Garenne Lemot, Clisson

THE STATUE – Front view of classical statue on pedestalThis shot demonstrates the beautiful tonal range achieved through pull processing

The Theory: Pulling Two Stops

For those who aren’t deep in the film weeds, here is what I actually did. By setting my camera to 100 ISO while using 400 speed film, I was overexposing by two stops.

Now, common wisdom says that pulling HP5 to 200 ASA (one stop) is perfectly fine. But I thought I was pushing my luck pulling it two stops to 100 ASA. I thought I was taking the mickey with the film gods.

By giving it extra light and less development, I was essentially asking the film to reduce contrast and grain significantly. I was testing just how much abuse it could take before the negatives turned into flat, grey mush.

I didn’t develop it for standard HP5 400 times. I treated the whole roll as if it were 100 ISO film from start to finish.


The Results

When I pulled the negatives out of the tank and held them up to the light, I braced myself for grey mush. What I got instead was dense, rich negatives — a bit chewy for the scanner, but nothing it couldn’t handle. And when the scans came up on screen, I just sat there for a moment.

The first thing that struck me was the shadows. HP5 at box speed can get muddy in the dark areas — a graininess that clogs rather than adds texture. Here, the shadows under the pergola and along the fence are deep and rich, but they’re not blocked up. You can still see into them. That matters.

FENCE WITH LONG SHADOWS – Diagonal shadows cast across gravel path – wood grain inside film grain. Both doing their job.

2. Texture and Grain

But the real revelation was the grain — or rather, the near-absence of it. Because the film had been drowning in light and starved of development, the grain structure in the mid-tones is almost Delta 100 territory. Look at the texture on that weathered wooden post. Every crack, every split in the grain of the wood — the film is rendering it, not obscuring it.

WEATHERED WOODEN POST – Close-up showing wood grain and textureThe fine grain structure is clearly visible in the wood texture

3. Highlight Control

I’d been braced for blown skies. Two stops of overexposure in spring sunshine — I was mentally preparing my excuses. But the reduced development had pulled the highlights back beautifully. Look at those bare branches against the sky. It’s a grey gradient, not a white void. The film held on.

BARE TREE BRANCHES AGAINST SKY, Garenne Lemot — I was expecting white sky. I got this instead.

4. Tonal Range

And then there’s the tonal range across the whole roll — from the white marble of the statues to the dark foliage behind them. The separation is superb. There’s a creaminess to it, a classical smoothness, that I’m honestly not sure I’d have got from HP5 at box speed. A happy accident, as it turns out, can sometimes produce results you wouldn’t have had the nerve to plan.

ORNATE URN WITH STATUE IN BACKGROUND – Layered compositionForeground and background detail with smooth tonal transitions
CLASSICAL COLONNADE – Stone pillars with cloudy skyWeathered stone texture and cloud detail demonstrate the technique’s versatility

The Verdict

So, was this a disaster? Absolutely not.

In fact, it might be some of the most satisfying film I’ve shot in a while — and I shot it by accident. The shadow detail is rich, the highlights are controlled, the grain is almost invisible in the mid-tones. It has that smooth, almost medium-format quality that you usually have to pay for in slower film and longer development times.

Ornate scrollwork detailRazor-sharp detail and micro-contrast prove no sharpness was lost

It turns out, what I thought was a stupid mistake is actually a technique some photographers use on purpose. Pull processing HP5 (rating it at 100 or 200 ISO and developing accordingly) is known to produce finer grain and lower contrast. I thought I was pushing my luck going two stops, but the film handled it like a champion.


Would I Do It Again?

Would I do it deliberately? Probably not — if I want 100 ASA film, I have 100 ASA film. But that’s almost beside the point now. What this roll taught me is that HP5 has reserves I hadn’t tested, and that sometimes the best thing you can do is commit to the mistake and see where it takes you. In for a penny, in for a pound — and in this case, the pound came back with interest.

If you ever load the wrong film, or find yourself caught between changing light and the wrong ISO setting, don’t panic. HP5 can take the abuse. It might even thank you for it.

Have you ever accidentally shot film at the wrong ISO? Did you save the roll or bin it? Let me know in the comments below.

Happy shooting

Ian from IJM Photography


P.S. The Kentmere 100 development time was a guess. An educated one, but a guess. The fact that it worked is either good research or dumb luck. Probably both.

P.P.S. I have since checked the ISO dial on the Nikon FE before every single roll. Every. Single. Roll.

P.P.P.S. The images from this roll are available as prints. Some accidents are worth keeping.

February 2026 — Clisson with the Nikon FE

Maybe I’m a little stubborn, just maybe, but I’m insisting on using my Nikon FE and for my health I have to get out. I had some Tri-X that needed using, and some HP5+ left over, so time to use it. And it does my mental health good too—getting out of the house despite the horrible light and rain.

“They” always say to go out in good light and use golden hour. We haven’t been blessed with good weather lately (understatement of the year contender 2026), and I always say just go out anyway and do it.

I shot two rolls that afternoon—72 frames total. Tri-X and HP5+, both at box speed. No pushing. I developed them in Fomadon LQN because it handles flat light cleanly: shadows stay defined, grain doesn’t get muddy even when the sky gives you nothing. When I scanned them, about half were ok enough to keep—36 frames that worked. Of those, maybe half a dozen were real keepers. That’s how it goes. Not every frame needs to be a masterpiece. Some just need to exist.

In Lightroom I only used the curves tool to pull a bit of separation between the wet stone and the grey sky. I wasn’t trying to manufacture contrast that wasn’t there. The rain had already done part of the work: cobblestones held texture because the light was even, puddles on the stairs created accidental reflections, and the streets were empty enough that I didn’t have to wait for tourists to clear the frame.

I won’t pretend I enjoyed standing in the damp. My shoes got wet. My hands were cold. But I needed to leave the house, and the camera gave me a reason to do it. The film was a deadline. The weather was irrelevant.

As you can see in the following photos, the light wasn’t fabulous, so we adapt. There are still interesting things to be seen.

Shot on Nikon FE with 50mm f/1.8. Kodak Tri-X 400 and Ilford HP5+ rated at box speed, developed in Fomadon LQN. Edited in Lightroom: curves adjusted for shadow separation only.

Opening of the Film Archives, Château de Clisson, February 2017

I had obviously taken a break with the Canon AE1 and spent the whole of December and January in hibernation, as most grumpy bears of my age do. Get Christmas over with, then go back to bed… I like my bed. No, I love my bed!!

Spring was just around the corner, and Kate had managed to awaken the beast and proceeded to tell me what she had planned for the day. It included me, a camera, and the Chateau de Clisson. I had just been “told” by my daughter, and off we headed to Clisson.

Now, the Chateau de Clisson is no small affair by any means. It dominates the centre of the town, sitting atop a hill as an imposing structure. I remember Kate having begged me on numerous occasions to actually go inside, and this time I acquiesced.

It was the perfect opportunity to not only document the inside of this historic site but also to let my playful daughter do what children do best: be cute, or as they say in French, espiègle. At that age, she was still content to pose for the camera, unlike the moody teenager she has become. Yet, sometimes, that same playful nature still manages to shine through.

If you’re curious to learn more about the history of the Chateau de Clisson, I’ve included a link for further reading.

After our outing in Clisson, I retreated to the quiet of my darkroom, where the real magic happens—transforming the captured moments into tangible memories. The familiar routine of developing the film, loading it into the tank, and watching the images slowly emerge never fails to captivate me. Once the negatives are ready and the scans are complete, I file them away in both my digital and analogue archives.

Then, a few years later, I get to share these memories with you. It’s a special kind of nostalgia—the kind that comes with taking time to slow down, reflect, and preserve what matters most. Thank you for joining me on this journey and for allowing me to share these pieces of the past with you.

The Opening of the Film Archives: An October Saturday in Town with Killian, 2016

Welcome back to another look at the film archives. This time, I’m sharing a few black-and-white street shots from an October Saturday in Nantes, likely taken with the Praktica MTL3 and HP5 Plus film. These outings with my son Killian, which we called ‘Ian and Killian days,’ became a cherished routine, a time for us to reconnect amidst the busyness of life.

He was 17 then, a weekly boarder at his lycée in La Roche sur Yon. On the weekends, we’d often head into Nantes, following the same familiar programme: a visit to the barbershop, a meal at the Sugar Blue café, and finally, a drink at the John Mc Byrne Irish Pub. In the photo, that handsome chap in the barber’s seat is Killian—a little reminder that it wasn’t always Kate joining me on these trips. These outings were a way to stay connected, despite his growing independence. Even with him being only 17, I still felt that sense of responsibility. Once a Dad, always a Dad.

As we went through our usual routine, I found myself facing the familiar challenge of capturing these moments on film. The low light inside the barbershop always made me second-guess whether I could get a decent shot without using a flash. But over time, I learned to trust the Praktica and the HP5 Plus film. There’s a rawness to film photography, especially with Ilford’s HP5. It adds a certain grit and texture to the image, something that digital just can’t replicate.

That’s what I love about film—the imperfections. The grain gives it character, a certain honesty that smooth, polished digital photos lack. It’s not about creating something flawless but about preserving the authenticity of the moment. This shot of Killian in the barbershop, for example, may not be technically perfect, but it’s real. It’s us, it’s Nantes, it’s one of those ‘Ian and Killian days.’

Looking back at these photos, I’m reminded that sometimes, it’s the imperfections that make an image truly memorable. Quite the day, right?