General questions about scanning

On this page we have collected general questions to the topic of digitalization. These questions are really basical, especially they are completely independent of any specific scanner.

Is the scan technology sufficient for archiving slides?

Many people have hundres, thousands or even ten thousands of slides stored in big closets and now there is the possibilty to digitize them with the help of modern film scanners and to archive them on a few CDs or DVDs. This saves the slides not only from quality lost but also relieves a lot of space in the closets for other purposes. Now the question comes up if the contemporary slide scanners are good enough so that one can start the digitlization, or if it is better to wait a couple of years, until there are newer devices on the market.

This question can be answered best if you look at the development of film scanners in the past years. By the end of the last millenium the maximum resolution of film scanners was about 2800 ppi. Today there are sscanners offering 4000 ppi. Maybe in a couple of years there will be scanners with much higher resolutions. A normal photographer, who has taken photos with a good SLR on normal films, seldomly has made photos, which have a higher resolution than 2800 ppi. That's why the development of film scanners in terms of resolution is practically finished.

The image quality of contemporary scanners is so good thanks to a big colour depth, that it hardly leaves any whishes open. If you make an image editing in the image editing software after scanning (i.e. tonal value correction, adaption of brightness and contrast), you can expect a digital photo as you know it from the projection.

So the contemporary film scannrs are so good that you can start digitizing your photo collection with good conscience. The actual (expensive) film scanners retrieve pratically all information out of a negative or positive. The scanning technology is so mature that you don't have to wait for a future generation of film scanners.

Can I wait for another 10 years until I digitize my slides?

Many semi-professional and hobby photographers have thousands of slides or negatives and have the strong intention to scan them all once upon a time in the future. We are often asked if it is better to that job now or if one can wait for another 10 years without care.

Each photographer knows or should know: Even if slides or negatives are stored in a cool, dark room, they become worse from year to year. That's why there is only one answer: scan them as soon as possible, since digital photos do not age.

Modern image editing procedure make the restrauration of old slides or negatives possible. In fact with such correction methods you don't make a new picture from a 30 years old slide, however, you can well correct 10-15 year old symtoms of age.

Is the digitalization of slides and negatives a simple matter?

For many people scanning of old pictures is a more troublesome than enjoyable matter. Finally, the old analog films have to be brought into the digital world only once, and then never again. That's why some scanner buyers hope that he purchaes a good film scanner, then scans his collection of slides or negatives in a short time, and then forgets the topic of scanning forever.

Scanning, however, is similar to photographing: A photo is made quickly, by pressing the trigger at the camera. However, for a really good photo it takes a lot of time, years of practice and experience. Also a scanner delivery a digital image quickly. However, until you achieve top image results by using the appropriate settings, a good scan software offers, it also takes a lot of exercise and experience.

So scanning has to be learned like photographing. You should plan a couple of weeks for learning before you scan a larger series of films. If you just buy a scanner and start digitizing your films it often leads to frustration after a couple of installation and set up. If you have scanned the first hundreds of films and then realize per accident that you achive significantly better image results with a specific setting, you have to start anew and the frustration even becomes bigger.

So the digitalization of old slides and negatives is really a large and time consuming task, which requires a lot of installation and training work. If you don't want to to that work, please, think about our Scan-Service. Then yo will get professional scans from high value film scanners and you can concentrate fully on the image editing work and sorting of the scans.

Scanning of slides and negatives is a time-consuming matter, which has to be learned first. Just buying a scanner and start scanning does not work in most cases. You have to invest a lot of time for learning handling the scanner and the scan software.

We recommend each scanner buyer to take about 3 weeks of time for training in the field of scanning, especially in order to get to know the scan software and different scan parameters in detail.

What can be scanned better, positives or negatives?

First it seems clear, that scanning of positives, no matter if they are framed or on a film strip, is simpler than scanning negatives. Finally on positives you have a real picture in front of you, which you can compare with the image on the screen. So you recognize already at the pre scan if the exposure of the scanner is ok and if the autofocus of the scanner has found the right setting.

At a negative you see an inverse picture on the film, which is additionally put under an orange mask. Only with much phantasy you can conclude from a negative to a real picture. The orange mask has to be corrected by the scanner software. It is hardly possible to see on the negative if it is right exposured or not. The big advantage of directly comparing a scan or a pre scan in the scanner software with the original is not possible at a negative.

On our site about density you can see that a negative film has a higher density range than a positive film. Because of this reason a negative film could be photographed much more easily than a positive film; photographers have made that experience often. Using a positive film the exposure setting has to be exact in the camera; the negative film forgives small exposure mistakes due to its large density range, i.e. they can be corrected better.

So for negative scans the scanner needs a higher density range, i.e. the scanner must be correspondingly high-value. Many flatbed scanners with integrated transparency unit fail at scanning negative films in high quality due to a too low density range.

Conclusion: A positive film is more difficult to photograph than a negative film; however scanning of a positive film is much simpler than scanning a negative film, both for the scanner and for the user.

How can negatives be scanned best?

Scanning of positives are an easy matter for any film scanner: The film is x-rayed and the transmitted light is measured by the singular cells in the CCD line. At negative scanning this matter is not so simple: A negative is not only an inverted positive, so that the measured colour values must only be inverted, but the negative has additionally an orange carrier layer, which has to be computationally separated. Additionally each film manufacturer has used its own film emulsion for negative films. Even from film sort to film sort different emulsions had been used. The consequence is that negative films strongly differ in their colour, exposure and contrast properties.

So one recognizes and maybe has already experienced that scnanning a negative film is a difficult matter and mostly requires a post process to get the right colours. Finally the film scanner cannot know which type of film is inserted, or can it somehow? beitung bedarf. Each film has above or below the real picture additional information of the manufacturer like the film sort and the speed, mostly in text form or as a bar code. If a scan software could read that text information or that bar code, which would technically be possible, however is not realized from any scanner manufacturer, the scan software would know which film has to be scanned.

The basic colour property of each film type are well known. Based on the exact identification of the film type a specific basic setting in the scan software can be set. And exactly this feature is offered by some scan programs. For instance, the reflecta scan software CyberView has included a couple of film profiles. But you better work with th scan software SilverFast, which offeres the selection of the inserted film in the so called NegaFix-dialogue, sorted by manufacturer, film type and film speed. Of course, the user has to read these information from the film strip manually, since there is no automatic recognition of that.

in most cases the exact choice of the film type brings significant improvements in the image quality. The time consuming post process of a negative scan si reduced to a minimum or even can be omitted. Because of that reason we recommend to use the SilverFast scan software to everybody who intends to scan negative films.

Does a film scanner make positives from negative films?

For positive scans the scan process is clear: A light source x-rays the film and a sensor measures the transmitted light. From the lightness of the singular colour tones the final image results. But how is this at negative scans? Does one obtain a "negative image from a negative scan, which has to be inverted in the image editing program in order to get a normal positve image? Or does the scanner to that work?

First we want to remark, that you don't get a positive from a negative just by inverting the colours, i.e. make black from white etc. In order to get a normal image from a negative, of course that colour inversion is necessary, however, additionally the orange carrier colour has to extracted. Since this carrier layer and the the film emulsion is different from manufacturer to manufacturer and from film type to film type, there are different calculation procedures necessary in order to optimally convert negatives into positives.

At modern film scanners the user does not need to take care of the negative-positive-transformation; the scanner or the scanner software, respectively, does this job automatically. It is one of the basic settings of each scan software to set the film type: positive, negative, positive black&white or negative black&white. If you choose negative as original you will automatically receive a positive image at the screen or in the output file. Due to the more complex scan procedure and the necessary inversion and correction of the carrier layer negative scans often take more time than positive scans.

In order to scan different film sorts and film variants of negative films optimally there are special different film profiles integrated in some scan software. More infos to this topic see our chapter about negative scans.

Why takes scanning negatives more time than scanning slides?

If you go through the data sheets and review of film scanners you notice again and again that the time for negative scans is higher than that for positive scans. Also many scanner user, who scan both negatives and positives, can confirm that there is a time difference between the two procedures. So why does scanning negatives take more time than scanning positives?

At positive scans the film ist just x-rayed and the transmitted light is directly conversed into pixels. At negative scans there is the additional colour inversion and the extraction of the yellow-organge carrier layer from the measured signal. So for negative scans there are more scan process steps necessary, in order to produce the final image.

If you have by accident scanned a negative film as a positive film, you may have noticed that the scan duration is even longer than that for a normal positive. But where does this come from, since you have just done a normal positive scan? The reason can be found in the image brightness. A correctly exposured negative is much darker than a correctly exposured positive. Film scanners, however, need more time to scan dark films than bright films. If you have ever compared the scan duration of a night photograph with that of a beach photo, you can surely confirm the above mentioned time difference.

My slide scans are too dark. What can be the reason for that?

A well known phenomenon at slide scanners is that the scans seem to be darker than the original is on the light panel or at the screen. Are the scans really darker or can something be done against it?

First we want to remark that a slide filme differs from a negative film in that the exposure time of the positive film must be exactly correct. A negative film forgives rather a small exposure error than a positive film. Often a whole slide film is under exposured. However, you often don't notice that if you project that slide series to a big screen with a bright lamp in a dark room. This leads that many photographers consider their mounted slides to be exposured correctly and think they are bright enough, although in reality they are a bit too dark.

Even for exactly exposured slides it can happen that the scans seem to be too dark at the monitor compared to a screen. In most cases the reason is a missing monitor calibration. So we strongly recommend to everybody who scans and edits photos, to calibrate his computer screen using a Toolkit to a worldwide standard. Only then it is guaranteed that the screen shows the scan or any digital photo in true and clear colours.

Only when a hardware based screen calibration is done and the scans are still too dark on the computer monutor, it is worth making appropirate correction in the image editing software concerning brightness and gradation.

How long are data safe on CDs or DVDs?

The effort of scanning a live's photo archive is very big. Ans many film scanner owners or scan service customers destroy their original film material after the digitalisation. One methode to save and archive the image data is to burn the image files on blank CDs or DVDs. But how long are the image data savely stored on such blank DVDs?

Lots of experts discuss this question. Whilst some blank producer talk about a lifetime of 100 years, many testers realize data losses already after 5 years. A usual durability nomber is 10 years. But can you trust such unsecure declarations?

No! If you burn all your digital photos on a series of DVDs and trust that you still can read them after 5, 10 yor 20 years without problems, you might make a big mistake. It might even happen that a self burned DVD cannot be read any more after a couple of days or weeks, e.g. if you buy a new computer with a new DVD-drive. So what can be done?

We recommend to store the image files on an external hard drive. If the capacy of the internal hard drive is not sufficient you have the possibility to plug an external hard drive to your computer. We recommend to make backups from this external hard drive again and again. It is definitely no mistake if you make a copy of your image archive every 1-2 years and still keept the old backups.

If you don't trust external hard drives, we recommend to copy the DVDs with the image files regularly (e.g. every 1-2 years) on new blank DVDs and keep the old DVDs anyway. A blank DVD does not cost much any more nowadarys, and a future generation of storage media will compress the content of many DVDs on only one.

How much main memory is necessary for processing high resolution scans?

If you scan a 35mm slide or negative with a resolution of 4000 ppi at a standard colour depth of 24 bit you will get an image file with approx. 20 million pixels.This image file takes about 60 MByte. If you save it as JPG the image file shrinks to approx. 5 MByte. However, if you open the compressed file in the image editing software it goes back to the original 60 MByte. So the JPG compression only saves space on the hard drive, not in the main memory when you open it.

In a time where each computer has a minimum of 512 MByte main memory 60 MByte are quite manageable. Anyway, the necessary main memory demand can increasy rapidly if you execute image editing functions and filters. If you apply a filter on a 60 MByte image, the necessary memory may increase to a factor of 3 (internal image duplicates, alpha-channels, space for computations etc.). On a PC with 512 MByte often there are less than 100 MByte left, since the operating system and other background applications use a main part of the memory. So a main memory of at least 1 GByte is recommendable.

At high end medium format scans the image files are much bigger. If you scan a 6x6 cm medium format film with 4000 ppi and 24 bit colour depth, the resulting image file will bei approx. 240 MByte. For an effective image editing process of such a scan you require 1 GByte main memory minimum. If you process image files with 48 bit colour depth the memory requisition doubles. For a comfortable image editing process of medium format films we recommend 2 GB free memory at least.

Some user my laugh now, because his computer has a mulitple of the above mentioned memory demands. However, often you don't edit only one image at a time, but you load a complete series of images in the image editing software and want to edit them quickly. If you load 10 or 20 images in your software you need a very large main memory, and an image editing program, which is able to use the provided memory at a time.

Does a very good SLR reach the imge quality of a very good film scanner?

At analogue SLRs one can state that their development phase is finished, whilst the development of digital SLRs continuously goes forward. Of course digital SLRs are very sophisticated and offer an impressing veriety of functionality, however, every year new models come to the market, which outshine the old models clearly. SO who is the comparison of a modern digital SLR with the combination of an old analog SLR plus a high end film scanner?

A couple of years ago even the best digital SLR could not keep up with the corresponding analog SLR in combination with a top film scaner. Nowadays the top models of digital cameras achieve values in terms of resolution and image quality, which had been achieved with the best analog cameras. However, the top models of digital cameras are still extremely expensive.

The resolution capability of analog films is limited by the film corn. But before this limit is achieved there is an other limit, namely the resolution limit of the lense, and this optical limit does not differ from the analog to the digital system. What you make in the analog area by choosing the film speed you do in the digital area by setting the ISO nomber. Only the very expensive digital cameras have full format CCD chips in the 35mm format, which don't show essential noise effects at high ISO nombers, and only these CCDs in 35mm format use the full lense range and have no focal length increasment factor.

The digital SLRs in the semi professional area do not achieve the quality and resolution of analog cameras in combination with very good film scannres. But they catch up from year to year, and one day they will win that race.

How many pixels are contained on a 35mm film?

In earlier times nobody has thought about the resolution of a 35mm film. Nowadays many proud owners of a 10 megapixel digital camera wonder, how many pixels there are on an old 35mm film. One can answer this question by considering some data: A 35mm film has an area of 36x24 mm and a resolution of 100-130 line pairs per Millimeter. A line pair is a pair of a black line next to a white line, i.e. 2 different lines next to each other. So 100-130 line pairs correspond to 200-260 pixels per millimeter.

So the computation of the total pixel nomber of a 35mm is like follows for 100 line pairs per mm: (36 x 100 x 2) x (24 x 100 x 2) = 7200 x 4800 = 34.560.000 Pixel. A normal 35mm with a resolution of 100 line pairs per mm contains approx. 35 million pixel. If it has 130 line pairs per mm this nomber goes up to 58 million pixel.

A film scanner with an effecitve resolution of 4000 ppi extracts about 20 million pixel from a 35 mm film, and a good digital camera makes 15 megapixel. Does that mean that a 35 mm film is still unachievable for the digital photograhy? A 35mm film may contain 35 or 58 million pixel on one picture, however, the camera, which exposures the film with its lense, is not capable to distinguish the captured light rays so detailed.

The limit is the resolution of the used lense. Simple zoom lenses have a resolution of only 30-40 line pairs per mm. High end lenses with fixed focal lense may have the double resolution. With 40 line pairs per mm only approx. 5,5 million pixels arrive on the film area, with 80 line pairs per mm approx. 22 million pixels land on the film. This means that in most cases the optics is not capable the exploit the complete resolution capabilities of the 35mm film.

The above mentioned of course also holds for digital cameras, since at digital cameras also the lense makes the picture, not the chip. A 15 megapixel chip never makes 15 million different pixels, if you use a cheap standard lense.

In the course of many years in the context of our Scan-Service we have made the experience, that a very good film like the Kodachrome film, which has been exposured with a very good camera and a very good lense, delivers approx. 20 million pixels of real information. This corresponds to a resolution of approx. 4000 ppi.

PC requirements for the use of a film scanner

How must a PC be equipped and configured for the user of a film scanner, so that scanning works without problems? We cannot answer this question flatly, since the requirements depend on the working fieldof the specific user. Most scanner manufacturer denote minimum requirements, so that the scanner and the scanner software work fairly.

Modern film scanners are connected to the PC with USB or Firewire interface. So your PC needs such interfaces. If it does not have them you can extend your PC by corresponding PC cards. It is important to know that each film scanner, which is made for USB 2.0 also runs at USB 1.1 interfaces however, the scan time increases significantly. For instance, if you scan a 35 mm slide with a resolution of 4000 ppi there will be 60 MByte transferred to the PC via the USB interface. Whilst this takes approx. one second with a USB 2.0 or a Firewire interface, it takes at least 40 seconds with a USB 1.1 interface according to the specification. Of course a USB 2.0 scanner can also be plugged to a USB 3 interface, however there is no speed increase because of that. That's why hardly a scanner manufacturer equips a scanner with a modern USB 3 interface.

To the PC itself: If you think that a scanner delivers final images to the PC, which only have to be stored on the hard drive, you are wrong. Much more the scanner only delivery raw data to the PC, which have to be processed to an image file by the scanner software. So you have an advantage if you have a fast CPU and much memory. You should use at least a Core i3 processor if you don't want to loos much time; of course a Core I5 is better and faster. A software which processes image files of 60 Megabyte in the 35mm field (or even 120 MByte at 48 bit colour depth) requires a lot of main memory. 512 MByte are an absolute minimum, however, 1 GB or more are recommendable.

The size of the hard drive is not important for the scan software, since it usually only takes a couple of MByte. Also, if you save your image files in the JPG format on the hard drive, you will net get into trouble due to the hard drive size. However, if you save your images in the uncompressed TIF format or save even raw data, you need a lot of space on the hard drive. At a resolution of 4000 ppi 1000 scans need about 50 GByte on the hard drive if you save them in the uncompressed TIF format.

If you edit high resolution scans in your image editing software you also need a fast CPU with much main memory. The main memory should be especially large, since the image editing software makes internal copies of the images and needs a lot of memory for applying filters and settings. You don't need a high end graphics card, since normal image editing functions are only in the two dimensional field. Modern graphics boards are optimized for the three dimensional operation mode.

An important element is the screen: No matter if you use an old CRT or a stat to the art TFT screen, you should calibrate it with a hardware tool like the Spyder. If you use a monitor which is not calibrated it shows all images in wrong colours. If you correct these wrong colours in the image editing software you correct the screen error indeed, and make the real images even worse. So the calibration of your monitor is indispensable.

Should mounted slides be better in glass or plastic frames?

These days most slides are put into plastic frames, which can be stowed well and sasavely in big magazins. However, there was a time, were glass frames were the top recommendation for slides. A main argument was that the film material was protected against exterior things like humidity and dust. But it turned out that glass frames offered more a short term protection than a long term protection, since humidity and dust, which attaches in the course of a long time between the film and the glass frame, causes much more damage to the film material than dirt which lies directly on the film. If molds come up between the glass and the film, the film material often is affected directly.

Which kind of frame is advantageous for scanning slides? Basically in the photography holds, that the reproduction quality of an optical instrument deteriorates with each glass plate or lense, which is used. Each part of glass absorbes a part of the light or has errors (reflexions, aberrations etc.). onen etc.). This becomes very obvious in the photography when you compare lenses with fix focal distance with zoom lenses with lots of moveable lenses.

Thus for scanning films you should use as few glass as possible. Because of that reason each flatbed scanner with transparency unit (2 glass plates used) is inferior to a real film scanner, which x-rays the film directly. So it is also clear, that the image quality is worse at glass frames compared with plastic frames. And the thicker the glass plates are the more light is absorbed. Dust, which lies between the glass plates, can be eliminated up to a certain level by hardware based scratch and dust removal procedures. Anyway you should clean the glass plates before scanning with a fine cloth.

Scanning becomes problematic when there are air bubbles or humidity bubbles between a glass plate and the film. These will be scanned exactly as you see them with your eyes. This looks awful at the screen and cannot be corrected, since the borders run right across the picture. In this case unly reframing in glassless frames helps. Another bad effect at glass frames are Newton rings. These are interference patterns which can be minimized, but not avoided, by using Anti-Newton glass.

However, there is one advantage of glass frames worth mentioning: Some very old slide has an extreme curvature on its surface. In a normal plastic frame it is not flat any more. At film scanners with a low depth of focus it may happen, that the image becomes partly unsharp due to the curvature. In this case glass frames have the advantage that they press the slide plain so that it lies flat in one level. In order to keep a slide flat in a frame there are a couple of special frames from a few manufacturers.

Conclusion: If you scan slides in glass mounts you must expect quality deficits. How strong these deficits are dependes on the condition of the glasses and the layer between the film and the glass. Reframing brings a quality improvement in any case.

Is the image quality at glass framed slides worse than at plastic frames?

For all optical instruments holds that the optical imaging performance deteriorates the more glass the light has to go through. Each glass plate reflects and absorbs light and has a series of optical image errors. A film scanner has the big advantage over a flatbed scanner that film material is x-rayed directly, i.e. two additional glass plates between the film and the scanner are avoided. This brings significant quality improvements.

Such quality improvements are nullified if you use additional glass frames for framing the slides. The glass plates which cover the positive also absorb and reflect light to undesired effects. Furthermore on the glass plates fine dust and dirt pile up. Additionally, between the glass plates and the film air and humidity bubbles can arise which will be scanned as you see them with your eyes. Such error patterns are extremely annoying and can hardly be corrected in the image editing software, since they run right across the image. An additional quality loss arrives due to interferences: Newton rings can hardly be corrected in the image editing software.

It generally holds that you should avoid glass at scanning films as much as possible, in the ideal case you use a film scanner with out glass plates and scan slides which are mounted in glassless frames. Each glass plate, either in the scanner itself or when using a glass film holder or at the slide mounts leads to quality deteriorations, which might be more or less strong according to the property of the used glass plates.

Is it worth reframing slides from glass to plastic frames?

As above described the image quality of scanning slides in glass mounts is worse than that for slides with frames without glass. The grade of the quality deterioration depends on the property and the state of the glass frames. So the question, if it is worth reframing the glass mounted slides, cannot be answered in general; not in any case you will achieve quality improvements. However, even a scan of a slide in a glass mount can yield an acceptable quality if the slide within the glasses is in a good state.

Often it is sufficient to clean the glasses with a fine cloth in order to achieve significant quality improvements, so that you can do without reframing. Reframing the slides is always necessary if there are clear bubbles between the glass an dthe film, since they will be scanned by 100% and hardly can corrected later in the image editing software. In this case the effort of reframing is much less than a time consuming image editing process.

So we recommend for the practice the scan a small series of glass mounted slides in order to make the decision if you can live with the resulting image quality or not. If you recognize too many negative effects you should take the effort of reframing the slides. Finally you digitize your slides only once and you will later enjoy better colours and images with fewer disturbancies.

Why does a JPG file become smaller if a multiple scan is done?

Very good film scanners have the possibility to make multiple scans. Thus the image noise is becoming reduced: Even if you have a high value scanner it happens in dark image areas hat singular pixels become faulty in terms of colours, e.g. on a black surface singular pixels become yellow, red or green. Of course you can detect it only in the 100% view. A multiple scan samples the original several times in order to eliminate such faulty pixels. Modern scanners offer the possibility to make 2-fold, 4-fold, 8-fold or even 16-fold scans.

If you create JPG files you may notice that such multiple scans make the image file smaller, and the smaller the higher the multiple rate. A scan with 4000 ppi may have an image size of 10,0 Megabyte at a one-fold sample. If you make a 2-fold sample the image size may shrink to 9,8 Megabyte. Where does this reduction come from?

At a JPG compression similar image structures are compressed strongly. Simplified you can imagine that as follows: If there are 10.000 blue pixels on a surface, not 10.000 individual pixels are saved but rather the amount of 10.000 and the approximate location of the pixels (it is really very simply expressed in this way). Unique faulty pixels however require the definition of an additional colour area and saving singular pixels. This means that more data have to be stored so that the JPG file becomes bigger. If those faulty pixels are removed by a multiple scan the image becomes smoother and more consistent, so that the compressed data amount becomes smaller, i.e. the JPG file becomes smaller, too.

Note: A smaller JPG file is an indication that the multiple scan has done a good work, even if you cannot recognize it at the first glance.

What is better, to make the image editing before or after scanning?

A scanner samples the film with a CCD sensor (normally a line sensor) and sends the raw scan data to the connected PC, where the scan data are processed in the scan software. In this scan software you can set specific scan parameter like the automatic exposure measurement or a 4-fold scan, the real processing of the data, however, is done after scanning in the computer. This means that to each scan process belongs an image editing step.

Adobe® Photoshop® Elements is available in our online shop.

There are a lot of image editing steps like the setting of the brightness, contrast or colour, which you can make before the fine scan (with the help of a prescan)in the scan software or you can to them in the image editing software after the fine scan. If you make simple tests before and afterwards you will come to the result that you can achieve the same image results, no matter if you make the settings in the scan software or in the image editing software. Mostly after the scanning you make an image editing, e.g. in Photoshop® in order to make additional image corrections (e.g. retouch work), so that you can to the simple image setting in this process, too. So you can do without that step before the scan process. If you have a magazine scanner or any batch scanner of course you don't want to make a prescan before each picture in order to make the image editing settings.

Forthe most film scanners it does not matter indeed, if you make the image editing settings before or after the scan. At films which need a strong image editing, i.e. a high contrast enhancement, it plays a decisive role if you make it before or after the scan process. If you make a normal scan with 24 bit colours, i.e. with 256 tone values per colour channel, and make a tone value bracing in the image editing program you may see colour cuts in the image because too few tone values remain. If you make the same tone value bracing in the scan software you will geht a full tonal value spectrum with 256 values. However, this only holds for high value scanners which send their raw data not in 24 bit but in 48 bit to the computer. In this case the scan software calculates from the 48 bit tonal value field (65536 tonal values per colour channel) a suitable 24 bit spectrum (256 values per channel), i.e. it does the tonal value bracing in the 48 bit field and not in the 24 bit field.

If you want to make such a tonal value bracing in the image editing software after scanning, we recommend to make 48 bit scans instead ov 24 bit scans (16 bit at black and white scans instead of 8 bit). Then the resulting image files have enough information for an elaborate image editing process.

Even if professional scan programs like SilverFast Ai Studio include powerful image editing functions included, the better and more simple solution is the image editing in image editing programs like Photoshop®. In order to avoid quality losses like described above it is recommended to make 48 bit scans.

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