Developer test: Spur Acurol-N

A while back I wrote about the new Spursinn developer being stocked by AG Photographic and had a question and answer session with Heribert Schain of Spur. Following that post, Heribert very kindly sent me a package of products for review and this is the first test I've done.

Acurol-N is a black and white developer that the company says is, sharp, fine-grained and long-lived. It's particularly recommended for use with Ilford Delta 100 so that's what I used for the test, rating the 35mm film at the box speed. By way of comparison, we'll be seeing how it does up against good old D76, a developer that has always got on well with the Ilford film.

The review set up was as follows. To test for grain and accutance, I photographed a scene out of a bedroom window using a Yashica 100mm f3.5 ML macro lens, which I know to be nice and sharp, on my Contax 137MA. Then, to see how the developers coped with both deep shadows and bright highlights, I took photographs from the top landing in my home with a 28mm Zeiss Distagon, a scene that included dimly-lit stairs and window light. I also shot some frames that were under- and over-exposed to see how the developers coped with that.*

The camera was tripod-mounted throughout. For the 100mm macro, the aperture was f8 and focus was on the bowling club clock. With the Distagon, I chose f5.6 and focused on the window frame. The apertures were the same for all shots with the shutter speed being changed for the bracketed shots.

The D76 was developed according to the massive dev chart - 11mins 1+1 at 20C -  and was spot on. I've found Spur's development times to be on the long side for my taste so I reduced the recommended 14.5 mins to 12.5 mins and that was about right. Acurol can be diluted up to 1+100 but for Delta 100 at 100 ISO, the recommended dilution is 1+70 at 22C with agitation of 30 seconds at the start and one inversion every two minutes. The water I used was distilled. Both sets of negs came out nice and clean and vice-free.

No peeping!
Since we're photographers here and not pixel-peepers, I resisted the temptation to scan the negatives at 3200 dpi and show 100% sections. Instead, I blew up the negatives under the enlarger (Durst L1200) to the equivalent of 20x16 inch prints (EL-Nikkor 50mm f2.8 lens) and printed a section of that image area on 10x8 Silverprint RC proofing paper which is actually quite nice stuff. If differences don't show up under those conditions then they're not worth bothering about in my opinion. Keep in mind, though, that the actual darkroom prints are of a higher quality than the crappy scans that emerged from my aged Espon scanner.

Before showing the results, I have to say that I wasn't really expecting to see any earth-shattering differences between the developers. I'm of the belief that the differences between developers - or films - designed to produce much the same results will, surprise, surprise, produce much the same results when you use them. In fact, for many photographers, there will probably be as large or larger differences as a result of variables in the development process using the same chemicals or film as there will be between different makes of materials. But don't let that put you off experimenting with different materials if the mood takes you. YOLO (you only live once) as my daughter is fond of saying in response to just about everything.

So here's what I found. There IS a marked difference between the results from the two developers. Acurol, like Ilford FP4 when it debuted back in the late 1960s, should be marketed as, "The sharp one". Acurol is a bit like Rodinal in that it can be diluted greatly and, with reduced agitation, produces enhanced edge effects. This Eberhard effect gives the edges some real bite and shows just how sharp 35mm negs can be. Hopefully you'll get an idea of what I'm talking about from the print section scans. The effect is obvious enough when I hold the prints close up but diminishes in the scans.

The test scene


Let there be grain
There's a price to be paid in that the grain is more apparent but it, too, is beautifully crisp. I don't have a problem with grain provided sharpness is retained. It's when you get mushy grain and low-accutance in the same shot that you're in trouble. Don't get me wrong: grain is still well-controlled and only a little more obvious than with D76 - but D76 grain looks woolly in comparison. If you look at the pics above, you can see the difference in grain and hopefully sharpness but remember this is a section from a twenty-inch long enlargement. And the difference in grain largely disappears at normal viewing distances (so, too, to some extent, does the difference in sharpness, to be fair to D76).

If I'd used D76 as a stock solution then the grain difference would have been greater because of the solvent effect the developer has on grain when used like that but sharpness would have suffered. At 1+1 the solvent effect is reduced and the edges get a little sharper so I thought this would be a better balance of qualities to pitch against Acurol-N.

The negs I exposed to show how the developers handle shadows and highlights were less successful in that I really didn't see much difference. D76 had a slight edge in the way it retained highlight detail but there wasn't a lot in it. Exposure was the same for both sets of negs and the shadows looked, to the naked eye, identical. Despite the high dilution of Acurol-N, I didn't see anything in the way of a compensating effect where the highlights are concerned. However, neither set of negs blocked up when over-exposed two stops and it would have been easy enough to print the highlights if I'd wanted to. I've included scans of two prints below but it's very difficult to see any differences. If you compare the top window areas you'll maybe spot that D76 has a little more detail.



Acurol-N does seem very sensitive to changes in development time and particularly agitation so you have to be careful and precise when using it. A couple of films I developed previously in Acurol-N at Spur's recommended times were quite dense. The up side of this is that the developer, according to the manufacturers, does a good job when seeking to contract or expand the tonal range for zone system or contrast control purposes. Spur also caution that water hardness can have a significant effect on development and advise the use of distilled/deionised water when preparing the working solution.

Hexar AF, Agfa APX 100, Acurol, Silverprint paper

Contax 137MA, 28mm Distagon, Agfa APX 100, Acurol,
Silverprint paper

Acurol-N isn't the best-known developer on the market but it deserves to be right up there with the best of them. It produces superbly sharp, clean negatives, nice robust tones, very controlled and crisp grain and prints well under the enlarger. Acurol-N's data sheet has times for a long list of films at dilutions ranging from 1+25 to 1+100 and provides contraction/expansion times for zone system workers.

It was quite a pleasant surprise to me to see the quality I could get from 35mm medium-speed negatives. A 20-inch print is perfectly acceptable in terms of grain and sharpness at normal viewing distances and I'm not that easy to please. Just when you're at the point where 35mm negative detail is beginning to break up, along comes Acurol to give the apparent sharpness a boost and the print a little extra headroom. Zeiss lenses (and the 35mm f2 Hexanon on my Hexar AF), Ilford Delta 100 and Acurol have given me probably the sharpest 35mm negs I've ever had without resorting to materials like the old Kodak Technical Pan and Technidol - which were a bugger, to be honest. Based on this test, I'd be happy to standardise on Acurol-N for all my black and white films. I can't wait to develop some 120 film in it.

Unfortunately, I'm not aware that there are any UK stockists of Acurol-N. You can get it at MacoDirectPhotoImpex and Spursinn themselves but maybe there's an opportunity for some UK companies to offer it? (Update: It's been pointed out to me that Spur products are available from in the UK. You have to register with the company to see prices but there is quite a list of developers and other chemistry. Well worth a look).

Buying it on the Continent, it works out at about £16 plus postage for 250ml but bear in mind that it can be diluted at up to 1+100 and even 1+200 in some situations so it's likely to prove very economical, especially given its long shelf life which is a very useful quality for those photographers who perhaps don't shoot lots of film.

Even at 1+50, the 250ml bottle will develop more than 40 rolls of 35mm film reducing the cost per film to around 38p and that compares very well with even fairly standard developers that don't last as long.

The next Spur product I'll be looking at is HRX-3 New developer, a fine-grain brew, which I should be in a position to write about in a couple of weeks.

* I used the sticky tape technique for the test film which allowed me to shoot all the necessary frames within a short space of time on the same roll. It worked perfectly.


  1. Thanks for this test. I have not heard of Acurol but I am willing to try it. Sometimes I think my 35 mm negatives lack some sharpness and this developer might help. It is good to see a blogger testing analog products.

  2. Thanks for the review, Bruce. I'm currently having a blast with HRX-3 film dev, using it for almost all my recent rolls, and I'm looking forward to reading your views on it.

  3. A very in-depth review bruce. Thanks for putting the work in!

  4. Good, review, I liked the sticky tape part, I still haven't tried it. John

  5. ...have given me probably the sharpest 35mm negs I've ever had without resorting to materials like the old Kodak Technical Pan and Technidol...

    What about Rollei ATP or Adox CMS 20?