Saturday, September 13. 2008
[D]ynamic range is one of the most misunderstood concepts out there. It's not that people misunderstand what it is in the abstract; rather, it is the practical application to photography that seems to be the hangup.
- Dante Stella
Dynamic Range (DR) is itself a confusing issue and comparisons of DR between film and digital take this confusion to a whole new level. Some very credible references declare the digicam the winner in this regard; others just as firmly stand behind film. So, does film have more DR than digital or not?
This question turns out to be more complicated than it sounds. Any blanket claims that "digital has greater DR than film," or vice-versa, are not useful as they gloss over the many technical differences between film and digital photography. Any responsible comparison must consider:
What follows is my admittedly imperfect attempt to compare film and digital DR and "see for myself." In comparing one representative digital and one film camera, I have tried to hold as many factors constant as practical. To that end, I printed a step wedge target (available below), taped it inside a cardboard box, and headed for a local camera shop on a cloudless midwestern summer afternoon.
Upon arrival I announced my intentions and requested a digicam of moderate cost that could store images in raw format on my Secure Digital (SD) card. Surprisingly, no compact digicam in the store would save raw files; the lowest cost option was an entry level DSLR, Nikon's D40. When I asked to go outside with the D40 (the better to test in direct sunlight), my salesman proposed to accompany me. While giving legitimacy to my activities, this also constrained my ability to experiment as the salesman insisted on "helping" me configure the camera. Worse, once we had defeated the D40's automation (ASA, aperture, auto flash, etc.) and to set it to "raw" mode, it became apparent that it was capturing only monochrome images. The salesman's struggles to defeat this having failed (and salesman plainly discouraged), we switched to the next floor model up, a Nikon D60.
Having deautomated the D60 to the best of our abilities (no simple matter; see the 200 page owner's manual if in doubt), I was finally free to photograph. Or so I thought: the sight of a grown man sitting on the sidewalk aiming a camera into a cardboard box proved irresistable to an elderly pair of woman shoppers and we were forced to pause briefly and acknowledge their incredulity.
Back to the test. I had locked the D60 at aperture F11 and film speed at ASA200, disabled the flash and set aperture priority. Now the light meter wanted to follow the autofocus and autofocus didn't want to focus on the step wedge target (too dark?)! In the name of expediency I settled for center weighted metering rather than attempt to manually meter and focus the D60.
The product of our efforts was 10 NEF files on my SD card, most of which were out of focus or badly exposed, but a few acceptable for this test. I thanked the salesman for his help, and found the next part of the experiment much easier: set film camera aperture and shutter, aim, focus, shoot, advance film and repeat. I ran the machine rather than it running me and finished this part of the test in no time. The experience of using these two cameras could not have felt more different.
Below are two images of the same scene outside the camera shop, taken within a few minutes of each other. The subject is a step wedge target taped inside a cardboard box with a backdrop of the shopping center in full sunlight. The first image was obtained with the Nikon D60, its 18-55mm VR lens set as near as I could approximate to focal length 40mm, saved to this raw (NEF) file. Settings recorded in the file are:
The D60 has the following characteristics:
The second image was obtained using 35mm Kodak Gold 200 print film with a Leica 40mm FL Summicron C lens, having the film processed at Walgreens, and then scanning the film with a Nikon Coolscan IV driven by VueScan scanning software. By coincidence, the Coolscan IV and D60's NEF both store data in 12 bits of precision.
Both cameras were set to ASA 200 with an F stop of 11, median exposure was as metered by each camera. I bracketed several images with both cameras, and performed all post-processing with VueScan, which can process .NEF files in the same way as scanner data. Using VueScan I adjusted each image so the step wedges were as nearly identical as possible. To accomplish this without loss of information I first set white point to .002 for each image, then used black point, brightness, and white balance to produce visibly similar output with minimal pixel clipping according to VueScan's linear color histogram (below). Next I chose the pair of images in which the values in the step wedge were closest.
In summary, my results were as follows:
Since I matched on the step wedge, the significant differences below are in what appears outside the shadow box. Both images are overexposed in this area, but the sidewalk and sky areas in the D60 image are more washed out than in the Kodak Gold 200 image:
Kodak Gold 200
Below are full resolution crops of the above two images in the shadow area, to display film grain versus sensor noise in this, another key area related to DR:
Kodak Gold 200 detail
Nikon D60 detail
While darker areas of the step wedge show roughly equal noise, lighter areas of the D60 image are cleaner. However, these lighter areas also exhibit less contrast than Kodak Gold, squares 25 through 45 being nearly equal to their neighbors on the right. So while we have less noise, we also have less contrast information in the D60 image, hence less effective range. Either image can be post processed to increase contrast, but this increases noise also.
In this test a high-end consumer digicam falls short of normal consumer color print film in the area of DR. Granted I didn't let the D60's ASA "float" or use Nikon's "Active D-Lighting" in this test; either of these may have avoided highlight blowout. But I also did not use the lowest contrast film available, professional film processing, or the best available scanner. So I feel that while far from perfect, the test is not unfair.
Does this "prove" film has greater DR than digital? No, but it may indicate consumer print film has a DR advantage over a relatively large, expensive, and complicated digicam. I think it tends to disprove the idea that digital has an obvious DR advantage over film, as I expect a comparison with a typical (smaller sensor) consumer digicam would show even greater DR superiority for film. Would a larger digicam's DR have exceeded Kodak Gold 200? Quite possibly, but so would professional grade film, or Kodak Gold in a larger format.
For me the upshot of this test is, the DR question is far from closed. More testing is needed, which is where YOU come in: don't rely on someone else's findings: get out there, test, see for yourself, and please report back. As I've shown, you don't even need to own the equipment!
To this end, here is the step wedge image file I used to generate my target. I printed it in color with a Canon ip8500 inkjet printer on HP high resolution paper, setting the printer preferences to "high resolution paper" (high resolution or better paper is needed to produce solid black tones). I'll publish any thorough results submitted here; please include:
For more on Dynamic Range, see Dante Stella, More is Less Is More: The Devil is in the Dynamic Range.
For insight about measurement of density range and bit depth, I also recommend Wayne Fulton.
For a filmmaker's perspective on the DR controversy, see Juan P. Perierra, Dynamic Range, Latitude and the Quest for Digital Film.
R. N. Clark, Dynamic Range and Transfer Functions of Digital Images and Comparison to Film is one of the most frequently cited web resources on the topic of film versus digital DR. Comparing a professional digital camera with 35mm film, Clark came to the conclusion that "Digital cameras, like the Canon 1D Mark II, show a huge dynamic range compared to either print or slide film, at least for the films compared."
Ken Rockwell, Film vs. Digital Cameras is also frequently cited. Rockwell comes to a different conclusion: "CCDs and the related capture electronics will need about ten times more dynamic range (three stops) than they have today to be able to simulate film's shoulder....This is the biggest image defect in digital cameras today."
That's all for now. To all, thanks for reading and happy image acquisition, by whatever means! - Carson Wilson
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I shoot 200 gold mostly sometimes 800max or ektar 100.
I hate digital, But all in all you have to compare the two formats in their respective print methods. I sugest 200 printed chemicaly in a darkroom and dslr printed at self serve photo printer at drugstore. That's what the two formats were intended to be.
Much thanks for your work. I too shoot mostly gold 200 having great results enlarging to 11x14 selling at a local gallery in Slidell, LA. Actually, I've got one image 11x14 hanging that was shot using kodak color 400!
I contantly get grief for shooting film (when found out). I get something on the order of "gee can you image what you could do with a digital camera?" No, not really. My Nikon FMs and I do great work and I'm happy. Why change when there is film to be had?; film that is still evolving and getting better I may add.
Also, film is relatively cheap. The great thing about film is that it forces you to stop, look and compose for better photographs and more "keepers."
The art of photography is not with digital technology with the exception of the most dedicated pro photographer using a multi-thousand $ camera.
The average consumer believes, without sound reasoning, that digital is better allowing for aimless "free" clicking. As you have demonstrated, digital is newer and has its place, but digital technology is not hands-down better than film photography. Jim
If you want to compare dynamic range in this photo, also consider the sky and the concrete in these photos above. In the film image, the sky and the concrete have more preserved detail. In the D60 image, the highlights are blown out and the detail is washed away to white. That is one of the bigger differences between film and digital. If shooting on a bright day, color negative film is better. If shooting in low light, use a digital camera with high ISO abilities.
IMO, the most bad thing modern both digital and film photography is total automation. One who never use full-manual and take full-auto camera in his hand is doomed to became just pseudo-photographer. Real photography requires huge knowledge and huge experience in manual control. Only with developed manual skills one can take full-auto camera and make as good shots as he did before. Photographer who did not know well technical and scientific side of photography and rely on expensive camera is just camera user - not photographer. No matter film or digital, SLR or point-and-shoot even pinhole!
Sure film is superior in sense of dynamic range but on digital side there is exposure bracketing and CMOS sensors able making lightning speed series of shots giving results close to film or even outperform last in DR.
For example I have some experience making high resolution and high DR using cheap point-and-shoot camera with no in-camera exposure bracketing at all. I shoot dozens of 6 Mp photos, precise stitching and blending them in software and result is amazing and unreachable to single shot of any expensive digital or film photo.
P.S. But nostalgia for full manual control and for good old film makes me buy film recently and borrow my father's Zenit-E with Helios 44-2 prime lens and I just feels the power of meditation
Carefully preparation for single shot takes some time, it gives a chance to calm mind and to take a step over the routine and rush, not to just see the object of photography but to feel it or even melt myself with it. No matter good or bad prints will be - it cannot cancel meditation experience and satisfaction. Good prints will be just additional bonus but it will not add much to shooting time experience
So even modern digital cameras with some tricks can outperform film in both DR and resolution, film must live: you can not check immediately on LCD whether shot was made good or bad. It remains unknown, and even this fact alone require calmness of mind: you did some act now but you cannot receive instant response or immediate consequence. Just as in Karma Law It make take some time to see how good or how bad it was done. And we must live that time well and remember: no matter of possible consequences if we dare to act - we must act as well as it possible, and when consequences came we remember - we did is as good as possible. This is the way to perfection