Sam North
17th of October 2004 (Sun), 06:11
I've edited this post again this time including the finsihed article lifted dirtectly from my site. See the actual web pages for related images.
I've been interested in the responses from here and elsewhere, and I've learned again that on the Web it's all too easy to pass on and listen to misinformation! In balance, after considerable research and after taking advice, I've concluded that in practice scanned slide film and DSLRs respond to light in much the same way.
Negative film does much better across the range, but the appearance of grain in the final scan is off-putting for some. However, fine grain in film like Fuji Reala can be further reduced by a little overexposure (see end of essay) and is of little consequence at typical viewing distances. Fine art shots are not really possible with 35mm film, so grain should not be a major reason for not shooting film.
Thanks for reading it.
Sam
From SLRs to DSLRs
Adjusting to Digital Technology
For the keen amateur photographer, DSLR photography is very convenient. No longer do we have to be as frugal as we were with film – we can take literally hundreds of shots† over a few hours at a variety of ISO settings and, within a short period of time, view every image in detail on a computer screen. Better still, DSLR photography allows us to assess each shot in the field by consulting the histogram and thumbnail image on the LCD. This means there are few excuses for wasted shots!
However, there are also several bothersome disadvantages associated with small format DSLRs. Their cost, including storage cards, compared to similarly specified 35mm cameras is off-putting to say the least, and for many cash-strapped amateurs full sensor DSLRs are out of the question for years to come. Battery-charging and image cropping are other concerns. Image cropping happens because the image sensor is smaller than a frame of 35mm film, the size conventional lenses are designed for. This alters the focal length of most lenses that project an image too large for the sensor.
Although small sensor DSLR photographers can enjoy the benefits of longer focal lengths because of image cropping, they must also face up to the problems associated with the increased focal length of wide-angle lenses. With Nikon and Canon DSLRs a 28mm lens will typically become something like 45mm. So, most who buy a small sensor DSLR will almost certainly have to buy another lens or two to compensate for this wide-angle deficiency. So, what’s the actual cost of a DSLR if you already own a wide-angle lens? (Many are less than impressed with the quality of so-called digital lenses packaged with DSLRs.)
The major players out there are busy producing exceptionally wide “digital” zooms to cash in on this lucrative market, although aberrations remain an ongoing problem for many. For example, the expensive small format Nikon AF-S 12-24mm f4 produces noticeable colour fringing in areas of high contrast. None too impressive at £900. DSLR red/blue fringing, caused by the angle at which light strikes the sensor, will show up in the corners and edges of your images.
There are a couple of other problems worth mentioning. No matter how careful you are, tiny specks of dust will accumulate on the surface of the sensor and will eventually need to be removed. And finally, your DSLR shots will soon tell you that sensors inherently struggle to record highlight detail. This last difficulty needs to be examined in more detail...
Losing Detail in the Highlights
You may come across knowledgeable photographers who write about “the shoulder portion of the D/log E curve” and how film “tends to roll off smoothly in the shadows and highlights.” They use terms like these to describe the efficient way film – especially negative film – responds to light. Unlike film, however, the sensors in DSLRs do not have the capacity to gradually and smoothly cope with highlight information. In the real world this means that the brightest areas of the scene can all too easily retain no information at all – no image data is present, just pure white. The sensor abruptly blows it.
This means that DSLR photographers, especially those who shoot landscapes, for example, will need to do all they can to accommodate the highlights, referring constantly to the histogram. Digital techniques and/or a grey graduated filter are often essential to balance the brightness of the sky with the land below. If you are new to DSLR photography, try experimenting with the RAW format so that you can exercise more control over highlight detail. When the image is converted, you can fine-tune the image by using levels and curves (the latter especially useful and powerful) in image-editing software.
Generally speaking, the DSLR photographer should take care not to blow the brightest parts of the image, although smaller blown highlights do not take away from the overall appearance of the shot, and are sometimes unavoidable. Contrast Masking* and Digital Blending techniques can be used when there are highlight areas within the scene that need to be balanced with shadow detail to extend the tonal range. Digital blending – a very flexible method – can be used with two or more images. The conscientious digital photographer will need to learn how to use good image-editing software. (Highlights are less of a concern when using negative film [see Scanning for 35mm Film]. Try to hold detail in the shadows and if necessary use a graduated filter. Always meter off a mid-tone, and bear in mind that it can be useful to overexpose negative film slightly.)
“Meter a medium-toned area as medium and the whites will be white, and the blacks, black” is not particularly good advice for the DSLR photographer learning to cope with the demands of electronic sensors. Also, as often as possible it’s helpful to push the exposure to the point where the histogram shows more information to the right of the display, without the severe abrupt peaks that indicate blown highlights.
Digital Technology and Film
When you press the shutter button on a DSLR, the shutter opens allowing light passing through the lens to strike the photosensor which is positioned in the lens’s focal plane, right where film would be in a conventional SLR. The information gathered by the sensor is passed as a stream of electrical signals that are converted into digital data before being processed by an electronic imaging ‘engine’.
The elements of an image recorded by Digital Single-lens-reflex cameras (reflex here refers to the light that is reflected by a mirror and pentaprism) are known as pixels, and the tiny elements of film are called grain or clouds of dye, depending on the film type. As film ratings and DSLR ISO settings are changed to cope with reduced light, for example, ISO 800, a digital image produces what is known as noise and film produces more grain.
While many prefer DSLR noise to film grain, others like the look of grain produced by faster films. Of course, it's possible to create a grainy look in software. It’s worth remembering at this point that slow slide film like Fuji Velvia (ISO 100) and high quality ISO 100 negative film, like Reala, produce very little grain. A digital image recorded at a low ISO rating will have no noise and on-screen especially will appear much cleaner than a film image.
If you are new to digital technology but still have a capable SLR, you may be debating whether you should sell it on or continue to use it alongside a digital camera. If you’ve been a keen photographer for years you’re sure to have a collection of film strips and slides. The best of these can be scanned and then enhanced on a computer using software like Paint Shop Pro, Corel PHOTO-PAINT, Photoshop and Adobe Elements.
Currently, 35mm film can be scanned in great detail to produce images larger than those produced by consumer DSLRs like the Canon 20D. Interpolation will be necessary to enlarge a small sensor DSLR image to the size of a quality consumer film scan (see link below for more information on interpolation). However, DSLR images enlarge surprisingly well while a larger film scan for a bigger print means larger grain! But bear in mind that the distance from which a large 35mm film print will be viewed will make grain of little or no consequence. Not only that, scanning software and image-editing techniques also have a major role to play, enabling the photographer to minimise the effects of grain in the final print.
Apart from the unavoidable, though not insurmountable, difficulties associated with scanning dusty slides and strips of negatives, a very persuasive reason for the modern amateur photographer phasing out film might be the cost of converting individual frames to digital. Having film scanned is expensive, and probably not an option at all if you’re heavily into street photography, or a documentary style of imagery. However, all is not lost.
If you like how fine-grained film looks and want to continue shooting it (and many do) you may want to consider investing in a quality film scanner. Unfortunately, it may cost about as much as a lower-end consumer DSLR. Alternatively, you could have each entire roll of film professionally developed and scanned to an economy package CD, or opt for economy 6x4 prints or a contact sheet; then you could take your time choosing the “keepers” (consider the points raised in Lose the Dead Shots!). The resulting small collection of best slides or negatives could then be returned and scanned to a much larger size for you to work with, before sending them off again to be digitally printed. Another option is to print the larger images out at home.
All of this seems like a serious amount of hassle compared to simply shooting with a DSLR and downloading images from the card. But if your style of photography means you don’t really shoot a lot of film, it may not turn out to be that expensive in the long run. Large prints from scanned film can be very impressive.
† Your DSLR will allow you to shoot smaller image sizes, but it's rarely a good idea. Invest in larger storage cards, shoot the largest size possible and resize in software if necessary. That way your images will suit every purpose.
* In software, a desaturated and inverted (negative) black and white copy of an image can be blended with the original to expand the tonal range. The increased density of the b&w inverted copy will be added to the original. To learn more about this method and other techniques that control the contrast range, search the Web for Digital Blending and Contrast Masking (originally a conventional darkroom technique). Mastering image-editing software is essential for the dedicated enthusiast who wants to get the very best from his or her DSLR, or scanned film.
__________________________________________________ ________________________
The Negative Advantage
Some people compare DSLR technology to 35mm film and in so doing seem to imply that film is just too long in the tooth. But in truth, film is different and has its ongoing advantages too.
It is often said that colour negative film is very forgiving of exposure errors. When underexposed, it's usually possible to rescue the image. But even when negative film is exposed properly, it hasn’t fully realised its potential.
Highlight, grain and sharpness
The highlight detail in colour negative film develops much more than the detail in the shadows. This means negative film can easily withstand a stop or two of overexposure. Overexposed negative film will easily retain more highlight detail than slide film or DSLRs, and the detail in the shadows will be increased, too.
The layers and chemicals in overexposed negative film will work together to actually reduce grain and enhance sharpness. But it’s important to remember that pushing the film too far will cause these gains to break down. So just a stop or two is ideal.
Reducing colour casts
Colour casts are significantly reduced when negative film is overexposed. When exposed normally to daylight, each layer gets sufficient exposure, but if the prevailing light source is unbalanced, an unpleasant cast will result because one or more of the layers gets too little exposure.
Overexposure will boost the starved layer without harming the others. So the orange glow so typical of indoor light and the greenish cast from fluorescent light will be less noticeable. Again, too much exposure will undermine the benefits.
Why Scan Colour Negative Film?
Gone are the days when 35mm negative film was known simply as "print film", preferred by amateurs for their economy prints and unpopular with pros. Even though viewing slides is less than convenient, for decades many advanced amateurs have preferred them partly because the alternative, negative film, has to be printed and is therefore a second-generation image. Today, with the introduction of good quality consumer film† scanners, the balance has shifted significantly. Both slide and negative film originals can be scanned in great detail and the resulting images digitally printed. This process has effectively narrowed the traditional gap between colour negative film and slide film. This is good news for amateurs who don't want to project slides and those who would rather shoot colour negative film.
The industry-standard reproduction process scans slide film with an image sensor, the light passing through to record as much detail and tonal quality as possible, although the loss of shadow detail in the original and on the printed page is not to everyone's taste. Unfortunately, colour negative film is not suitable for this expensive, professional process, which is one reason why slide film has been the preferred choice of book publishers. However, good consumer film scanners allow the modern amateur to work at home on original images. Scanning and image-editing software programs can be used together to impressively control the tonal range, contrast, colour saturation and grain. In fact, it's now possible to minimise the effects of grain so that it's not an issue in the final print at typical viewing distances.
Shooting fine-grained colour negative film allows you to hold excellent shadow detail while largely avoiding the pitfall of the lost highlights that can be a regular problem with slide film and DSLRs. As a consequence, exposing colour negative film properly is less difficult and the sharp and tonally rich negatives give you more information to work with in the digital darkroom where tonal and colour information in 20+ megapixel images can be manipulated creatively to produce quality, saturated digital prints. As with all digital images, it's also possible to produce impressive black and white prints from colour originals (see page Beyond the Channel Mixer). The only real problem with shooting colour negative film is getting quality scans that make good use of colour and tonal information across the range — not everyone is prepared to invest in a decent 35mm scanner that captures very good highlight and shadow detail (dynamic range), and some labs may not produce the results you need.
Slide Film or Colour Negative Film, or DSLRs?
Particularly in the context of scanning for prints, what’s the real difference between 35mm slide film and colour negative film? And, to logically expand the discussion a little further, are there any tangible advantages to shooting with a DSLR rather than either of the film types? We can easily reach a conclusion at the very beginning! Despite the fact that the fruitless Slide Vs Neg Vs Digital Sensor debate occasionally raises its head in photo forums, there is in truth no definitive answer that will satisfy everybody. For the discerning small format amateur — and the SLR amateur photographer is the overall context of this site — it’s often a matter of personal choice, with advantages and disadvantages built into all three options.
Clearly DSLR photography is very convenient and flexible with more shooting options geared to particular styles. Photojournalism, general action photography, aspects of wildlife photography and even the more casual pursuit of that special image will all benefit from digital technology. Although consumer DSLRs are more expensive than comparable film SLRs, there are no film and processing costs to take into consideration, and for many photographers, amateur and professional, this is a significant advantage. And digital is immediate, with no long delay beween shooting and viewing. However, a 35mm amateur photographer with a very different style of photography — landscape, or still-life, for example — may not see these benefits as particularly appealing. A lot depends on the individual's approach and output, and for many today, 35mm film is still an attractive and viable option, especially if the film can be scanned at home and manipulated in image-editing software.
Various terms are used to describe the inherent properties of film. The curious amateur photographer will read about exposure latitude, dynamic range, tonal range and even scenic range. To simplify this diversity you only need to understand that slide film and negative film respond differently to the tonal values in the scene you intend to record. Or, to put it another way, the range of illumination in the scene, all the way from the darkest shadows to the brightest highlights, will be handled differently depending on the choice of film. A film’s ability to capture shadow and highlight detail is known as its dynamic range. Confusingly, slide film has less tonal range than colour negative film but more dynamic range.
Colour negative film’s propensity to hold very good tonal values accounts for its much wider exposure latitude. Colour negative film has lower contrast properties than slide film and will cope quite well with highlight and shadow detail, perhaps up to five stops of light: three overexposed and two underexposed. In real world amateur photography this means that properly exposed fine-grained colour negative film will capture very good shadow detail while also retaining subtle tonal gradations in the brighter areas of the scene – clouds, for example, or sunlit Caucasian skin tones. So, because negative film copes so well with highlights, before you take your shots you should try to make sure you’ve captured as much relevant detail in the shadows as possible. Colour negative film, with its broad gradations of tone, is ideal for scanning because there’s a lot of useful information across the range to work with.
However, when compared to slide film, colour negative film’s wide exposure latitude usually means the recorded image has less contrast and saturation – it clearly has less bite! More than that, the orange mask built into negative film can present unique problems, with consumer scanners offsetting its effects with varying degrees of success. As a result, getting the best colour balance may occasionally take a little effort. In the final analysis, however, scanning techniques and image-editing software can inject punch and zest into colour negative images and this in turn means more vibrant, appealing prints. In other words, you can give them more bite!
Positive (slide) film has more lively contrast and vivid colour than negative film. It also exhibits smoother tonal blends and remarkably fine grain. It’s unfortunate then that it struggles to hold detail in the highlights, and very dark shadows can be rendered almost black. Before exposing slide film it’s best to make sure preference is given to the brighter parts of the scene. It's possible to compensate for the wide contrast range in a landscape scene by using graduated filters. The slide photographer can also use common image-editing techniques that impressively expand the exposure latitude of any scene by combining two or more scanned images.
Digital sensors share slide film’s highlight problems but will get more from the shadows. Shadow retention will be particularly good if the exposure, when appropriate, is routinely pushed just short of blown and unprocessed and uncompressed data is captured rather than JPEG. If this isn’t possible and the subject being photographed allows for it, two or more images can be used to substantially expand the range, as mentioned above. Sensor pixels, or light receptors, wrestle with bright light because their response to it is not gradual. Instead they peak quite quickly, totally losing highlight data. Digital camera manufacturers are working on this problem but the application of their technological advances has been less than ideal. It’s certainly an irritating problem that makes some digital exposures quite tricky, like shooting slide film, and it's likely to be an integral part of DSLR technology for quite some time to come.
Regardless of how you capture an image, it’s worth remembering that considerable tonal information will always be lost in the print. Various techniques can be used to expand the information in an image, whether it’s on film or created in a digital camera. The result should be a print with shadow and highlight detail that more accurately depicts the original scene. An image that has not been manipulated will probably produce a print with less apparent dynamic range. This underscores how important it is to familiarise yourself with image-editing software and so make proper use of the digital darkroom. A hi-res JPEG image converted to a lossless format for editing has more latitude than you might expect and unprocessed data straight from the camera (RAW) will allow you even more control, when necessary.
† Attachments for quality flatbed scanners cannot compete with dedicated 35mm film scanners.
I've been interested in the responses from here and elsewhere, and I've learned again that on the Web it's all too easy to pass on and listen to misinformation! In balance, after considerable research and after taking advice, I've concluded that in practice scanned slide film and DSLRs respond to light in much the same way.
Negative film does much better across the range, but the appearance of grain in the final scan is off-putting for some. However, fine grain in film like Fuji Reala can be further reduced by a little overexposure (see end of essay) and is of little consequence at typical viewing distances. Fine art shots are not really possible with 35mm film, so grain should not be a major reason for not shooting film.
Thanks for reading it.
Sam
From SLRs to DSLRs
Adjusting to Digital Technology
For the keen amateur photographer, DSLR photography is very convenient. No longer do we have to be as frugal as we were with film – we can take literally hundreds of shots† over a few hours at a variety of ISO settings and, within a short period of time, view every image in detail on a computer screen. Better still, DSLR photography allows us to assess each shot in the field by consulting the histogram and thumbnail image on the LCD. This means there are few excuses for wasted shots!
However, there are also several bothersome disadvantages associated with small format DSLRs. Their cost, including storage cards, compared to similarly specified 35mm cameras is off-putting to say the least, and for many cash-strapped amateurs full sensor DSLRs are out of the question for years to come. Battery-charging and image cropping are other concerns. Image cropping happens because the image sensor is smaller than a frame of 35mm film, the size conventional lenses are designed for. This alters the focal length of most lenses that project an image too large for the sensor.
Although small sensor DSLR photographers can enjoy the benefits of longer focal lengths because of image cropping, they must also face up to the problems associated with the increased focal length of wide-angle lenses. With Nikon and Canon DSLRs a 28mm lens will typically become something like 45mm. So, most who buy a small sensor DSLR will almost certainly have to buy another lens or two to compensate for this wide-angle deficiency. So, what’s the actual cost of a DSLR if you already own a wide-angle lens? (Many are less than impressed with the quality of so-called digital lenses packaged with DSLRs.)
The major players out there are busy producing exceptionally wide “digital” zooms to cash in on this lucrative market, although aberrations remain an ongoing problem for many. For example, the expensive small format Nikon AF-S 12-24mm f4 produces noticeable colour fringing in areas of high contrast. None too impressive at £900. DSLR red/blue fringing, caused by the angle at which light strikes the sensor, will show up in the corners and edges of your images.
There are a couple of other problems worth mentioning. No matter how careful you are, tiny specks of dust will accumulate on the surface of the sensor and will eventually need to be removed. And finally, your DSLR shots will soon tell you that sensors inherently struggle to record highlight detail. This last difficulty needs to be examined in more detail...
Losing Detail in the Highlights
You may come across knowledgeable photographers who write about “the shoulder portion of the D/log E curve” and how film “tends to roll off smoothly in the shadows and highlights.” They use terms like these to describe the efficient way film – especially negative film – responds to light. Unlike film, however, the sensors in DSLRs do not have the capacity to gradually and smoothly cope with highlight information. In the real world this means that the brightest areas of the scene can all too easily retain no information at all – no image data is present, just pure white. The sensor abruptly blows it.
This means that DSLR photographers, especially those who shoot landscapes, for example, will need to do all they can to accommodate the highlights, referring constantly to the histogram. Digital techniques and/or a grey graduated filter are often essential to balance the brightness of the sky with the land below. If you are new to DSLR photography, try experimenting with the RAW format so that you can exercise more control over highlight detail. When the image is converted, you can fine-tune the image by using levels and curves (the latter especially useful and powerful) in image-editing software.
Generally speaking, the DSLR photographer should take care not to blow the brightest parts of the image, although smaller blown highlights do not take away from the overall appearance of the shot, and are sometimes unavoidable. Contrast Masking* and Digital Blending techniques can be used when there are highlight areas within the scene that need to be balanced with shadow detail to extend the tonal range. Digital blending – a very flexible method – can be used with two or more images. The conscientious digital photographer will need to learn how to use good image-editing software. (Highlights are less of a concern when using negative film [see Scanning for 35mm Film]. Try to hold detail in the shadows and if necessary use a graduated filter. Always meter off a mid-tone, and bear in mind that it can be useful to overexpose negative film slightly.)
“Meter a medium-toned area as medium and the whites will be white, and the blacks, black” is not particularly good advice for the DSLR photographer learning to cope with the demands of electronic sensors. Also, as often as possible it’s helpful to push the exposure to the point where the histogram shows more information to the right of the display, without the severe abrupt peaks that indicate blown highlights.
Digital Technology and Film
When you press the shutter button on a DSLR, the shutter opens allowing light passing through the lens to strike the photosensor which is positioned in the lens’s focal plane, right where film would be in a conventional SLR. The information gathered by the sensor is passed as a stream of electrical signals that are converted into digital data before being processed by an electronic imaging ‘engine’.
The elements of an image recorded by Digital Single-lens-reflex cameras (reflex here refers to the light that is reflected by a mirror and pentaprism) are known as pixels, and the tiny elements of film are called grain or clouds of dye, depending on the film type. As film ratings and DSLR ISO settings are changed to cope with reduced light, for example, ISO 800, a digital image produces what is known as noise and film produces more grain.
While many prefer DSLR noise to film grain, others like the look of grain produced by faster films. Of course, it's possible to create a grainy look in software. It’s worth remembering at this point that slow slide film like Fuji Velvia (ISO 100) and high quality ISO 100 negative film, like Reala, produce very little grain. A digital image recorded at a low ISO rating will have no noise and on-screen especially will appear much cleaner than a film image.
If you are new to digital technology but still have a capable SLR, you may be debating whether you should sell it on or continue to use it alongside a digital camera. If you’ve been a keen photographer for years you’re sure to have a collection of film strips and slides. The best of these can be scanned and then enhanced on a computer using software like Paint Shop Pro, Corel PHOTO-PAINT, Photoshop and Adobe Elements.
Currently, 35mm film can be scanned in great detail to produce images larger than those produced by consumer DSLRs like the Canon 20D. Interpolation will be necessary to enlarge a small sensor DSLR image to the size of a quality consumer film scan (see link below for more information on interpolation). However, DSLR images enlarge surprisingly well while a larger film scan for a bigger print means larger grain! But bear in mind that the distance from which a large 35mm film print will be viewed will make grain of little or no consequence. Not only that, scanning software and image-editing techniques also have a major role to play, enabling the photographer to minimise the effects of grain in the final print.
Apart from the unavoidable, though not insurmountable, difficulties associated with scanning dusty slides and strips of negatives, a very persuasive reason for the modern amateur photographer phasing out film might be the cost of converting individual frames to digital. Having film scanned is expensive, and probably not an option at all if you’re heavily into street photography, or a documentary style of imagery. However, all is not lost.
If you like how fine-grained film looks and want to continue shooting it (and many do) you may want to consider investing in a quality film scanner. Unfortunately, it may cost about as much as a lower-end consumer DSLR. Alternatively, you could have each entire roll of film professionally developed and scanned to an economy package CD, or opt for economy 6x4 prints or a contact sheet; then you could take your time choosing the “keepers” (consider the points raised in Lose the Dead Shots!). The resulting small collection of best slides or negatives could then be returned and scanned to a much larger size for you to work with, before sending them off again to be digitally printed. Another option is to print the larger images out at home.
All of this seems like a serious amount of hassle compared to simply shooting with a DSLR and downloading images from the card. But if your style of photography means you don’t really shoot a lot of film, it may not turn out to be that expensive in the long run. Large prints from scanned film can be very impressive.
† Your DSLR will allow you to shoot smaller image sizes, but it's rarely a good idea. Invest in larger storage cards, shoot the largest size possible and resize in software if necessary. That way your images will suit every purpose.
* In software, a desaturated and inverted (negative) black and white copy of an image can be blended with the original to expand the tonal range. The increased density of the b&w inverted copy will be added to the original. To learn more about this method and other techniques that control the contrast range, search the Web for Digital Blending and Contrast Masking (originally a conventional darkroom technique). Mastering image-editing software is essential for the dedicated enthusiast who wants to get the very best from his or her DSLR, or scanned film.
__________________________________________________ ________________________
The Negative Advantage
Some people compare DSLR technology to 35mm film and in so doing seem to imply that film is just too long in the tooth. But in truth, film is different and has its ongoing advantages too.
It is often said that colour negative film is very forgiving of exposure errors. When underexposed, it's usually possible to rescue the image. But even when negative film is exposed properly, it hasn’t fully realised its potential.
Highlight, grain and sharpness
The highlight detail in colour negative film develops much more than the detail in the shadows. This means negative film can easily withstand a stop or two of overexposure. Overexposed negative film will easily retain more highlight detail than slide film or DSLRs, and the detail in the shadows will be increased, too.
The layers and chemicals in overexposed negative film will work together to actually reduce grain and enhance sharpness. But it’s important to remember that pushing the film too far will cause these gains to break down. So just a stop or two is ideal.
Reducing colour casts
Colour casts are significantly reduced when negative film is overexposed. When exposed normally to daylight, each layer gets sufficient exposure, but if the prevailing light source is unbalanced, an unpleasant cast will result because one or more of the layers gets too little exposure.
Overexposure will boost the starved layer without harming the others. So the orange glow so typical of indoor light and the greenish cast from fluorescent light will be less noticeable. Again, too much exposure will undermine the benefits.
Why Scan Colour Negative Film?
Gone are the days when 35mm negative film was known simply as "print film", preferred by amateurs for their economy prints and unpopular with pros. Even though viewing slides is less than convenient, for decades many advanced amateurs have preferred them partly because the alternative, negative film, has to be printed and is therefore a second-generation image. Today, with the introduction of good quality consumer film† scanners, the balance has shifted significantly. Both slide and negative film originals can be scanned in great detail and the resulting images digitally printed. This process has effectively narrowed the traditional gap between colour negative film and slide film. This is good news for amateurs who don't want to project slides and those who would rather shoot colour negative film.
The industry-standard reproduction process scans slide film with an image sensor, the light passing through to record as much detail and tonal quality as possible, although the loss of shadow detail in the original and on the printed page is not to everyone's taste. Unfortunately, colour negative film is not suitable for this expensive, professional process, which is one reason why slide film has been the preferred choice of book publishers. However, good consumer film scanners allow the modern amateur to work at home on original images. Scanning and image-editing software programs can be used together to impressively control the tonal range, contrast, colour saturation and grain. In fact, it's now possible to minimise the effects of grain so that it's not an issue in the final print at typical viewing distances.
Shooting fine-grained colour negative film allows you to hold excellent shadow detail while largely avoiding the pitfall of the lost highlights that can be a regular problem with slide film and DSLRs. As a consequence, exposing colour negative film properly is less difficult and the sharp and tonally rich negatives give you more information to work with in the digital darkroom where tonal and colour information in 20+ megapixel images can be manipulated creatively to produce quality, saturated digital prints. As with all digital images, it's also possible to produce impressive black and white prints from colour originals (see page Beyond the Channel Mixer). The only real problem with shooting colour negative film is getting quality scans that make good use of colour and tonal information across the range — not everyone is prepared to invest in a decent 35mm scanner that captures very good highlight and shadow detail (dynamic range), and some labs may not produce the results you need.
Slide Film or Colour Negative Film, or DSLRs?
Particularly in the context of scanning for prints, what’s the real difference between 35mm slide film and colour negative film? And, to logically expand the discussion a little further, are there any tangible advantages to shooting with a DSLR rather than either of the film types? We can easily reach a conclusion at the very beginning! Despite the fact that the fruitless Slide Vs Neg Vs Digital Sensor debate occasionally raises its head in photo forums, there is in truth no definitive answer that will satisfy everybody. For the discerning small format amateur — and the SLR amateur photographer is the overall context of this site — it’s often a matter of personal choice, with advantages and disadvantages built into all three options.
Clearly DSLR photography is very convenient and flexible with more shooting options geared to particular styles. Photojournalism, general action photography, aspects of wildlife photography and even the more casual pursuit of that special image will all benefit from digital technology. Although consumer DSLRs are more expensive than comparable film SLRs, there are no film and processing costs to take into consideration, and for many photographers, amateur and professional, this is a significant advantage. And digital is immediate, with no long delay beween shooting and viewing. However, a 35mm amateur photographer with a very different style of photography — landscape, or still-life, for example — may not see these benefits as particularly appealing. A lot depends on the individual's approach and output, and for many today, 35mm film is still an attractive and viable option, especially if the film can be scanned at home and manipulated in image-editing software.
Various terms are used to describe the inherent properties of film. The curious amateur photographer will read about exposure latitude, dynamic range, tonal range and even scenic range. To simplify this diversity you only need to understand that slide film and negative film respond differently to the tonal values in the scene you intend to record. Or, to put it another way, the range of illumination in the scene, all the way from the darkest shadows to the brightest highlights, will be handled differently depending on the choice of film. A film’s ability to capture shadow and highlight detail is known as its dynamic range. Confusingly, slide film has less tonal range than colour negative film but more dynamic range.
Colour negative film’s propensity to hold very good tonal values accounts for its much wider exposure latitude. Colour negative film has lower contrast properties than slide film and will cope quite well with highlight and shadow detail, perhaps up to five stops of light: three overexposed and two underexposed. In real world amateur photography this means that properly exposed fine-grained colour negative film will capture very good shadow detail while also retaining subtle tonal gradations in the brighter areas of the scene – clouds, for example, or sunlit Caucasian skin tones. So, because negative film copes so well with highlights, before you take your shots you should try to make sure you’ve captured as much relevant detail in the shadows as possible. Colour negative film, with its broad gradations of tone, is ideal for scanning because there’s a lot of useful information across the range to work with.
However, when compared to slide film, colour negative film’s wide exposure latitude usually means the recorded image has less contrast and saturation – it clearly has less bite! More than that, the orange mask built into negative film can present unique problems, with consumer scanners offsetting its effects with varying degrees of success. As a result, getting the best colour balance may occasionally take a little effort. In the final analysis, however, scanning techniques and image-editing software can inject punch and zest into colour negative images and this in turn means more vibrant, appealing prints. In other words, you can give them more bite!
Positive (slide) film has more lively contrast and vivid colour than negative film. It also exhibits smoother tonal blends and remarkably fine grain. It’s unfortunate then that it struggles to hold detail in the highlights, and very dark shadows can be rendered almost black. Before exposing slide film it’s best to make sure preference is given to the brighter parts of the scene. It's possible to compensate for the wide contrast range in a landscape scene by using graduated filters. The slide photographer can also use common image-editing techniques that impressively expand the exposure latitude of any scene by combining two or more scanned images.
Digital sensors share slide film’s highlight problems but will get more from the shadows. Shadow retention will be particularly good if the exposure, when appropriate, is routinely pushed just short of blown and unprocessed and uncompressed data is captured rather than JPEG. If this isn’t possible and the subject being photographed allows for it, two or more images can be used to substantially expand the range, as mentioned above. Sensor pixels, or light receptors, wrestle with bright light because their response to it is not gradual. Instead they peak quite quickly, totally losing highlight data. Digital camera manufacturers are working on this problem but the application of their technological advances has been less than ideal. It’s certainly an irritating problem that makes some digital exposures quite tricky, like shooting slide film, and it's likely to be an integral part of DSLR technology for quite some time to come.
Regardless of how you capture an image, it’s worth remembering that considerable tonal information will always be lost in the print. Various techniques can be used to expand the information in an image, whether it’s on film or created in a digital camera. The result should be a print with shadow and highlight detail that more accurately depicts the original scene. An image that has not been manipulated will probably produce a print with less apparent dynamic range. This underscores how important it is to familiarise yourself with image-editing software and so make proper use of the digital darkroom. A hi-res JPEG image converted to a lossless format for editing has more latitude than you might expect and unprocessed data straight from the camera (RAW) will allow you even more control, when necessary.
† Attachments for quality flatbed scanners cannot compete with dedicated 35mm film scanners.