alan little’s weblog

blowhards on digital cameras

15th March 2004 permanent link

When I was in my between-weblogs period, I had a rather rude habit of writing my weblog in the form of excessively long comments on other peoples’. I haven’t been doing that so much lately, but I did today in the form of a response to some comments by Michael Blowhard on digital cameras. Here’s what I said, slightly tidied up and fact- and spell-checked.

Interesting post. Some thoughts:

MB: You know how digi-photos, no matter how dazzling, often look a little tight and flat? One of the reasons for this is that their exposure latitude is narrow.

Kinda sorta. Digital has much narrower exposure latitude than print film, but about the same as or slightly more than colour slide film which is what most pros (except wedding & portrait specialists) shot for years. So that in itself isn’t it.

Fact check the figures I found checking my bookshelf and the web for exposure latitude of film versus digital – i.e. the dynamic range of difference between light and dark in a scene that a camera can capture without having either highlights go completely white or shadows completely black – varied wildly. Around 5 or 6 f-stops was generally the quoted figure for both slide film and digital (although, as I mentioned next, highlight failure on slide film is slightly more gradual and forgiving). Colour print film has more range, maybe 8 or 9 stops. Black and white varies hugely depending on how it is exposed and processed, but figures well above 10 stops seem to be widely quoted. I also saw 10 or 11 stops quoted as the range the human eye can deal with.

More of an issue is that digital has no “shoulder” – that is, the light sensitivity is more of a straight line than an s-curve. With film, the amount of detail in blown highlights or dark shadows tails off smoothly; with digital, highlights just blow with no gentle tail-off.

There are a couple of interesting approaches to fixing this. One is software, as you mention – I’ve heard that Kodak’s new shadow retrieval stuff is excellent. Fuji have also announced a new SLR, the S3, which has sort of 6MP resolution but that consists of two 6MP grids, one of big pixels that are good for low light, one of small ones that are less likely to blow out intense highlights. They reckon that by reading the big ones, but then seeing if they can get a reading from the small ones in areas where the big ones are blown out (or something like that) they can get a dynamic range more like print film. Fuji’s digital SLRs so far have been very good indeed, so it will be interesting to see how this works out.

I’ve also read a theory that, because of the way different colour sensors are laid out on most current imaging chips, red is more likely to blow out, or has less resolution,  than other colours. This is said to produce the effect where digital images have less colour contrast and general "snap" and feeling of depth than good film images, and is again said to be not *too* hard to fix in Photoshop.

MB: The Kodak guy said that he and his colleagues think that a digiphoto would need 13-16 million pixels to match a tiptop film image.

That sounds about right for the very finest-grained 35mm films. You can see film grain clearly in images scanned at or above about 3000 dpi, so that says a piece of 35mm has an effective resolution in the region of 3000 x 4500 dpi =~ 13.5 “megagrains”. Note that there are a couple of 35mm style digital SLRs with this resolution, and there are professional studio cameras over 20 megapixels (also over $20k)

That’s for the very finest grained slow fims, shot on a tripod through a good lens – which, however, isn’t how 99.9% of photographs are taken. In particular, digital holds up much better than film for shooting at very high ISO in low light. Very fast film has huge and obvious grain and very poor colour fidelity; digital produces a lot of noise when shot at 1600 ISO or above, but that’s much easier to fix in software than blotchy grain and nasty colours. (Kodak’s digital SLRs are notoriously weak in this area, but Nikon and Canon are excellent)

A lot of people also seem to think that the absence of noise in good (SLR, low ISO) 6MP digital images more than compensates for the slightly lower absolute resolution (2000 x 3000 for 6MP versus 3000 x 4500 for 50 to 100 ISO film)

MB: He compared the current state of digi-photography to the early days of music CDs, when the sound they delivered – while brilliant and clear – was also cold and grating.

Sounds about right to me. Glenn Reynolds had an interesting piece a while back where he predicted that, as with analog gear in music and recording, the “warm look” of film will be a cult in a few years.

I’m thinking about selling my Hasselblad to buy a digital SLR, but I haven’t quite been able to bring myself to do it just yet. I will never sell my Nikon FM2.

I also completely agree with your previous post about horrible digicam ergonomics. There’s an interesting new Leica/Panasonic effort that sounds as if it addresses a lot of these issues, but it’s ridiculously expensive for a digicam ($1500 to $1800). My thoughts on that here. Ken Rockwell’s observations on digicam handling are spot on:

You have to wait for them to turn on, and then you have to wait after you press the button for something to happen. Even zipping through the annoying menus takes time; time I don't have. With these long delays you have to hope your subject doesn't loose interest or fall asleep while you're trying to get a photo.

… as are his no-bullshit general observations on what film and digital respectively are good for.

related entries: Photography

all text and images © 2003–2008