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Digital Photo Cataloging FAQ

Rocket Science?

You need to understand what you have in the way of photos and how you want to get these photographs out once you have put them in. Its not rocket science, just common sense.

Are you Digital?

You must ask yourself whether you are going totally digital or whether you want to be able to go back from a digital image to the original scanned slide/print/negative. If you want to go back to the original you should have a filing and reference system so you can quickly reference the original during image registration.

Better yet, let your image naming strategy refer to the location of the original.

Did you think about it before you started?

The main thing with designing the way you catalog your images is to sit down and think about it before you start. Cataloging images is not a trivial task and the last thing you want to do is have to go back and do them all several times just because you didn’t think of something up front.

One album or many?

The over-riding consideration for how many albums to create is album size. How are you going to back it up? For most of us that means a copy on cd-rom. Realistically in 650Mb you can expect to get 35,000 to 45,000 images per album depending on the size and quality of thumbnail that you choose. Monitor ongoing size and make plans accordingly.

So, just how do I catalog them?

Here is one approach.

Remember the KISS principle, Keep It Simple Stupid. If what you have come up with is complex, takes ages to register each photo, is prone to error then just maybe you need to simplify the approach.

The first thing to do is write down the different types of photos that you have. This might be things like family, friends, different hobbies, interests (travel). Don’t go overboard looking for differences, these should be the natural groupings that you think of.

For each different type of photo write down:

  1. Am I going to want to share these photos with anyone else (e.g. family photos, club photos)

  2. Are there any categories or structure within this type (collections, travel)

  3. Do any photos fit in several different types?

For each different type write down how you want to retrieve the images, e.g.

  1. I want to be able to pull out all photos of someone or something

  2. I want a time sequence set of photos for trip

  3. I want to see all photos of Johnny in time sequence

This is both how you want to find images and how you want to play a slide show from them.

You then need to decide what are attributes and keywords. Your photo types and any structure within them are almost certainly attributes while individual items specific to a single photo are keywords.

Is there anything special I need to do with my keywords?

Yes. You have to make sure that you use consistent naming strategies for each class of keyword or attribute. Look at peoples names for starters, you could use “John Doe” or “Doe, John”. Whichever you choose you should be consistent.

How can I make sure my cataloging strategy will work?

This is the most important step. Catalog a group of images according to the way you believe you want to work. Now set up Picture Sets to retrieve them to verify it is working the way you want. Modify accordingly. This provides you with proof that your concept of how you want to access your images will work before you go through the laborious process of registering them.

One last thing. Look for ways that you can make registering easier in the order you process images. CyPics uses commonality between successive images to cut down the work, maybe you can increase that commonality.

How do I keep track of master images and their offspring?

In CyPics the image name is irrelevant, the description used when you catalog it is far more important.

We suggest that you use a naming strategy that:

  • Assigns a unique names to each successive master images using an increasing number. You could use additional encoding information to include things like the year taken if desired.

  • Offspring names always append additional information to the master image name such that the master image is still identifiable within the name.

When should I backup my images and the image database?

We would recommend that you copy your master images to a multi-session CD-R as soon as possible after you have transferred them from the camera. If you are using a naming strategy for your master images then you should rename them before taking the backup copy.

With images you are working on, editing etc, you need a copy at suitable intervals so that you don’t potentially lose all your work in progress. For backing up these images we’d suggest using CD-RW (re-writable)  as these can be reused.

With the album database it is appropriate to take a backup periodically after you have been cataloging images. Do it whenever you would hate having to redo the amount of cataloging you have done since the last backup. Once again we’d suggest using several CD-RW (re-writable) CDs that you rotate through.

Some time after you have finished enhancing your images you will archive them to CD-R media and then get CyPics to update its image locations to reflect their new home. At some multiple of new archive CD creation we would recommend the writing of a permanent copy of the album database on CD-R.

Any serious backup strategy includes the storage of offsite copies. Ideally you will have a copy kept with the computer and another copy stored at another location where it can not be impacted by the same natural disaster.


Digital Photo File Formats

What are suitable file formats to use?

The four most common file formats used are:

  • TIF – Tagged Image File Format, uncompressed and compressed formats
  • PNG – Portable Network Graphics, standardized compression
  • JPG – Joint Photographic Experts Group, compressed format
  • GIF – Graphics Interchange Format, compressed format dating back to CompuServe in the 1980’s

Compression comes in two forms: lossless and lossy. Lossless compression loses none of the image information during compression and decompression. Lossy compression as its name says removes some of the original photographic detail. Lossy compression can reduce the size of image files to a far greater extent than lossless compression.

JPG is a lossy technique that is designed to compress color and grayscale continuous-tone images. The information discarded at lower levels of JPG compression is designed to be information that the human eye cannot detect. Please note that lossy formats such as JPG may result in the loss of additional detail each time you open and save a file. If the image format from your digital camera is lossy then your master copy should be the original image ex the camera or an immediate conversion to a lossless format. 

The following table shows characteristics of each of these image formats:

Format Color Depth Compression Loss of Detail on Saves Web
TIF variable lossless No No
PNG variable lossless No Yes
JPG 24 – lossy – – Yes – Yes
GIF – 8 – lossless No Yes
Note: Conversion to GIF suffers from an immediate loss of color depth from 16 million colors to 256. After that there is no further loss. Use of dithering results in limited image degradation for on-screen viewing. There is an example in the next section.

The next table shows the suitability of each format to particular applications.

Photographs Photographs + edges Line art, Drawings and Captured Screens
Image Type Real world images in 24-bit color or 8-bit gray scale Real world images with very sharp edges including text and lines Text, blocks of the same color or lines and sharp edges
Preferred format for Master Copy PNG or TIF PNG or TIF PNG or GIF or TIF
Master Copy ex Digital Camera If the camera produces a lossy format then the original image ex the camera or the immediate conversion to a lossless format.  If the camera produces a lossy format then the original image ex the camera or the immediate conversion to a lossless format.  not applicable
> 24-bit color PNG or TIF PNG or TIF PNG or TIF
EXIF retention TIF or JPG TIF or JPG TIF or JPG
Greatest compression JPG (JPG may not be suitable for master copy) PNG or GIF, GIF reduces colors to 256 but improves text, lines and edges  PNG or GIF
Redistribution JPG PNG or GIF PNG or GIF
Internet JPG GIF GIF
Interchange compatability TIF (not LZW) TIF (not LZW) TIF (not LZW)
Worst selection GIF reduces colors to 256, and is larger  than 24 bit JPG JPG smears text, lines and edges JPG adds smears to text, lines and edges


Note: TIF LZW has limited support as Unisys has a patent on the LZW compression algorithm used by both GIF and TIF with LZW compression. Not all companies choose to support it for this reason. It is a small loss as LZW is a relatively inefficient algorithm when applied to real world images, see the LZW compression results in the next section.

Should you compress images?

The following table gives the sizes of various image formats for an original image of 1830 x 1240 x 16 million colors.


Format Lossless Size (Kb)
TIFF – uncompressed Yes 7,942
TIFF – LZW Yes 6,650
PNG Yes 3,434
JPG – minimum compression No 1,478
JPG – 80 No 395
GIF No 1,801



Graphics images are often stored in a compressed format to save space on your hard drive and to maximize the number of images that will fit on removable storage such as CD-R.

The question was should you compress images? The answer is dependent on your needs.

  • While still manipulating images use a lossless compression format.
  • If you want to retain EXIF information the only alternatives are TIF and JPG.
  • When archiving (e.g. to CD-R) you should create at least two copies. One copy could be a lossyformat for viewing and the other a lossless master.
  • If you don’t need to retain a master copy (i.e. you are never going to change the image again) then you could consider doing both your archives in JPG format.

What is TIF file format?

TIF or TIFF is short for “Tagged Image File Format”. It was designed primarily for raster data interchange. Its main strengths are a highly flexible and platform-independent format which is supported by numerous image processing applications.

TIFF can contain multiple kind of picture formats, like uncompressed, LZW and Fax 3 & 4 formats. The header section of TIFF-file contains the information about the image, like the color depth, color encoding and compression type. Because of the flexibility, very different levels of image quality can be produced with TIFF. The current version is TIFF 6.0.

What is PNG file format?

The Portable Network Graphics (PNG) format was designed to replace the older and simpler GIF format and, to some extent, the much more complex TIFF format.

For image editing PNG provides a useful format for the storage of intermediate stages of editing. PNG’s compression is fully lossless–and since it supports up to 48-bit truecolor or 16-bit grayscale–saving, restoring and re-saving an image will not degrade its quality. Unlike TIFF, the PNG specification leaves no room for implementors to pick and choose what features they’ll support; the result is that a PNG image saved in one application is readable in any other PNG-supporting application.

For the Web, PNG really has three main advantages over GIF: variable transparency, cross-platform control of image brightness, and a method of progressive display. PNG also compresses better than GIF in almost every case, but the difference is generally only around 5% to 25%.

What is JPG file format?

JPEG (pronounced “jay-peg”) is a standardized image compression mechanism. JPEG stands for Joint Photographic Experts Group, the original name of the committee that wrote the standard.

JPEG compression is lossy, meaning that the decompressed image isn’t quite the same as the one you started with.  JPEG is designed to exploit known limitations of the human eye, notably the fact that small color changes are perceived less accurately than small changes in brightness.  Thus, JPEG is intended for compressing images that will be looked at by humans.  If you plan to machine-analyze your images, the small errors introduced by JPEG may be a problem for you, even if they are invisible to the eye.

JPEG compression is designed for compressing either 16 million color (24 bit) or 256 gray scale images of natural, real-world scenes.  It works well on photographs, naturalistic artwork, and similar material; not so well on lettering, simple cartoons, or line drawings.

A useful property of JPEG is that the degree of lossiness can be varied by adjusting compression parameters.  This means that you can trade off file size against output image quality. Most JPEG compressors let you pick a file size vs. image quality tradeoff by selecting a quality setting.  The quality scale is purely arbitrary; its not a percentage of anything.

For full-color images, the uncompressed data is normally 24 bits/pixel.  The best known losslesscompression methods can compress such data about 2:1 on average.  JPEG can typically achieve 10:1 to 20:1 compression without visible loss, bringing the effective storage requirement down to 1 to 2 bits/pixel.  30:1 to 50:1 compression is possible with small to moderate defects, while for very-low-quality purposes such as previews or archive indexes, 100:1 compression is quite feasible.  An image compressed 100:1 with JPEG takes up the same space as a full-color one-tenth-scale thumbnail image, yet it retains much more detail than such a thumbnail.

JPEG compression is poor on:

  • large areas of pixels that are all exactly the same color

  • icons that use only a few colors

  • very sharp edges: a row of pure-black pixels adjacent to a row of pure-white pixels, for example.  Sharp edges tend to come out blurred unless you use a very high quality setting.

  • small text that’s only a few pixels high

  • plain black-and-white (two level) images

If your image contains sharp colored edges, you may notice slight fuzziness or jaggedness around such edges no matter how high you make the quality setting.

It would be nice if, having compressed an image with JPEG, you could decompress it, manipulate it (crop off a border, say), and recompress it without any further image degradation beyond what you lost initially.

Unfortunately THIS IS NOT THE CASE.  In general, recompressing an altered image loses more information.  Hence it’s important to minimize the number of generations of JPEG compression between initial and final versions of an image.

There are a few specialized operations that can be done on a JPEG file without decompressing it, and thus without incurring the generational loss that you’d normally get from loading and re-saving the image in a regular image editor.  In particular it is possible to do 90-degree rotations and flips losslessly, if the image dimensions are a multiple of the file’s block size (typically 16×16, 16×8, or 8×8 pixels for color JPEGs).  This is of importance as many users of digital cameras would like to be able to rotate their images from landscape to portrait format without incurring loss — and practically all digicams that produce JPEG files produce images of the right dimensions for these operations to work.  So software that can do lossless JPEG transforms has started to pop up.  But you do need special software; rotating the image in a regular image editor won’t be lossless.

It turns out that if you decompress and recompress an image at the same quality setting first used, relatively little further degradation occurs. This means that you can make local modifications to a JPEG image without material degradation of other areas of the image.  (The areas you change will still degrade, however.)  Counterintuitively, this works better the lower the quality setting.  But you must use *exactly* the same setting, or all bets are off.  Also, the decompressed image must be saved in a full-color format; if you dosomethinglikeJPEG=>GIF=>JPEG, the color quantization step loses lots of information.

Unfortunately, cropping doesn’t count as a local change!  JPEG processes the image in small blocks, and cropping usually moves the block boundaries, so that the image looks completely different to JPEG.  You can take advantage of the low-degradation behavior if you are careful to crop the top and left margins only by a multiple of the block size (typically 16 pixels), so that the remaining blocks start in the same places.  (True lossless cropping is possible under the same restrictions about where to crop, but again this requires specialized software.)

The bottom line is that JPEG is a useful format for compact storage and transmission of images, but you don’t want to use it as an intermediate format for sequences of image manipulation steps.  Use a lossless24-bit format (PNG, TIFF, etc) while working on the image, then JPEG it when you are ready to file it away or send it out on the net.  If you expect to edit your image again in the future, keep a losslessmaster copy to work from.  The JPEG you put up on your Web site should be a derived copy, not your editing master.

What is GIF file format?

GIF, ‘Graphics Interchange Format’ was introduced in the 1980s on CompuServe to allow high-quality, high-resolution graphics to be displayed on a variety of graphics hardware and was intended as an exchange and display mechanism for graphics images. The rise of the Internet and in particular the web saw GIF usage explode.

Saving a photographic image as GIF firstly achieves a 3:1 compression by a reduction in color depth from 16 million colors to 256. A GIF graphic is stored as a sequence of pixels with 256 color values from a image specific color palette.  Dithering reduces the visual impact of the reduction in number of colors. This raster data is then compressed according to the LZW algorithm (Unisys patented).

GIF is potentially useful on those areas where JPEG compression is poor and where you are looking for a file size that is significantly less than PNG, that is for images having:

  • large areas of pixels that are all exactly the same color

  • icons that use only a few colors

  • very sharp edges: a row of pure-black pixels adjacent to a row of pure-white pixels, for example.

  • small text that’s only a few pixels high

  • plain black-and-white (two level) images

GIF does significantly better than JPEG on images with only a few distinct colors, such as line drawings. Not only is GIF lossless for such images, but it often compresses them more than JPEG can. For example, large areas of pixels that are all exactly the same color are compressed very efficiently indeed by GIF. JPEG can’t squeeze such data as much as GIF does without introducing visible defects.

Digital Cameras Travelling FAQ

How do you manage thousands of photographs taken on the move?

Just how do you manage all the photographs you may take on an extended holiday with a digital camera? The alternatives are getting better:

  • Take enough removable media
  • Take a notebook computer
  • Use Digital Labs
  • Carry extended storage devices

Camera storage media is expensive and who wants that big an investment in media that won’t fit your next camera upgrade. It isn’t worth it.

Carry the notebook – and this was supposed to be a holiday. Great you carry around this notebook computer for four weeks and in the fifth week the computer gets stolen. No pictures, no computer, just an insurance claim.

More and more photo shops are hanging out the digital sign. Most digital camera storage devices can easily be transferred to CD-Rom and other innovative options.

High volume storage devices (digital wallet, Clik! Drive)also allow you to transfer camera storage to disk.

What is needed for viable digital photography on the move?

Viable digital photography for extended travel requires several things:

  • Being able to empty your digital cameras storage media to take more shots
  • No compromise on image quality to fit more on the camera media
  • Transferring images to durable long term storage within a short time frame
  • Not having all your eggs in one basket with a notebook computer or a digital wallet

After you transfer images from your camera to your computer do you take a backup? Do you consider one copy of your photographs on a notebook computer, digital wallet or Clik! disks durable storage?

The Internet is not likely to do anything to help, the total size of the photographs you take precludes emailing them home or using temporary storage on the web. You need them offloaded onto cheap media as you go and for convenience you need someone else to do it for you.

The Digital Photo shop provides most of the answers. You can dump the photos onto a computer while you wait and then come back in a little while to pick up your freshly cut CD. Purchase mutiple CDs and mail one home for safe keeping.

Is it time to throw away that old conventional camera?

The time has probably arrived unless you have a professional quality conventional camera with assorted lenses.

  • Digital storage options have vastly improved in the last few years.
  • Good quality small digital cameras are far more affordable.
  • High quality digital cameras with SLR bodies and interchangeable lenses are too expensive for most people to consider value for money.

Digital Photo Resolution

What is resolution?

The closest analogy that digital photography resolution has to conventional film is grain. Normal film is not a continuously variable media it is limited by the underlying granularity of the light sensitive film. Grain tends to increase as light sensitivity (ASA rating) increases. Regardless of what you do you can’t get more detail out of a negative than what the grain permits.

The equivalent to grain in digital photograph is the pixel, the pixel is a single point in the image that can take on any one of many millions of colors. Image sizes in digital photography are measured by the number of pixels wide by the number of pixels deep. This is the same measurement as used for computer screens, for which typical measurements are 800 x 600, 1024 x 768, 1280 x 960.

To put it another way a digital photograph is an image that is made up of millions of dots, each one of which can take on any one of millions of colors. Got the picture?

PCs and resolution, is more better?

Like anything else to do with computers Yes and No.

Yes, the greater the resolution of the screen the more detail that can be displayed of a photographic image. Also associated with this is the dot pitch which simplistically is the diagonal distance between each pixel. The smaller the dot pitch, the sharper the image. However, very small dot pitches may also translate into decreased brightness and contrast.

A secondary affect of increasing the display resolution used on a screen is that the standard size of windows text characters decreases as you increase the resolution. It can get to the point where you can no longer read the screen and are forced to use big fonts in display settings. The problem here is that some programs won’t work when you use big fonts, their windows become garbled with missing text,  missing fields etc. In general life is easier if you can use the windows default font size.

Another problem is that all early screen sizes were in the ratio of 4:3 horizontal to vertical resolution, that is 640 x 480, 800 x 600 and 1024 x 768. Some recent video cards have options such as 1280 x 1024, a 5:4 ratio. It is wiser to stick to the 4:3 ratio choices as often graphics created or manipulated on a system running with a different ratio will not look the same when transferred back to the standard 4:3 ratio. It is also possible on a 5:4 ratio screen that the aspect ratio of photographs may be distorted.

How much resolution do I need?

You can do many tricks with digital images but the one thing you can’t do is add resolution to a photograph after it has been taken. This is the main thing you have to make sure is right before you take the next photograph with your digital camera.

You have to ask the same question when you scan images. Too much resolution takes time, consumes memory and rapidly fills your disk. Too little and you need to go back and scan it again.

The table below shows typical uses and suggested resolutions for both using a digital camera and scanning images.

Digital Camera Scanning Photos
Print a standard size photograph
(6″ x 4″ or 7″ x 5″)
1800 x 1200 to 2100 x 15002.2 mega-pixels to 3.2 mega-pixels 300 dpi scan. Higher scan resolutions generally achieve little to no visible improvement in printed image quality.
Full screen PC based slide show You can get away with half your current screen resolution for now but with the future in mind we suggest as a minimum at least 1800 horizontal pixels. See the note that follows.
E-mail to a friend or to post it on the Web 600 x 400 72 or 100 dpi scan. This saves disk space and time moving the image over the Internet.
Enlarging (10″ x 8″) Use a conventional camera You need at least 300 dpi in the output result. For ten inches that is 3000 dots. Divide the 3000 by the width of the input image to get the minimum scan resolution. If 6″ then the minimum scan resolution is 500 dpi.
Note:  A PC based slide show is different in that you can expect your display resolution to change several times over your lifetime. In many cases the photographs you put on CD today will be handed down to successive generations. You could be starting today on a 17″ screen with a resolution of 1024 x 768 and ultimately displaying on a full size wall unit of far greater resolution.The higher the initial resolution the less raggedness there will be when images are resized to fit any screen size. You cannot target image sizes to a specific screen size as the screen size will change with time. If possible work with a minimum of at least 1800 horizontal pixels.Fortunately images do enlarge on-screen quite well. Doubling the width and height increases the image area by 4 times. Provided software that uses resampling is used acceptable quality is obtained.

How big are digital images?

Digital images are BIG. They use lots of memory and consume lots of disk. Lets look at  some examples.

Image Size Uncompressed Size
2 mega-pixels 8 Mb
1024 x 768 3 Mb
3000 x 2200
(10″ x 8″ enlargement)
26.4 Mb


Digital Photos and PCs

What is color depth?

Color depth is the number of colors that are supported by an image format. The color depth is set by the number of bits used to store the color of each pixel.

  • 1-bit file supports two colors (usually black and white)
  • 8-bit file supports 256 colors
  • 24-bit file supports 16 million colors
  • 32-bit file supports 4 billion colors

24-bit, 16 million colors, incidentally, is considered true color as it provides a greater number of colors and shades than the human eye can distinguish.

The higher the color depth that is supported by an image format, the more space the files take up on your hard drive.

With digital photography color depth and resolution are the two important facets of image quality, you would rarely reduce the number of colors in an image if you wanted to retain quality.

Note: In computer terminology 8-bits make up one byte.

How big are digital images?

In the resolution FAQ we provided the example:

Image Size Uncompressed Size
2 mega-pixels 8 Mb
1024 x 768 3 Mb
3000 x 2200
(10″ x 8″ x 300dpi)
26.4 Mb

How do you calculate the size of an image?

To calculate the uncompressed size use the formula:

 [Horizontal Pixels] * [Vertical Pixels] * n = Number of bytes


n =  4 (for 32-bit color, 4 billion colors)
n =  3 (for 24-bit color, 16 million colors)
n =  2 (for 16-bit color, 65 thousand colors)

How much memory do I need in my PC?

Regardless of whether you use compressed images or not, an image is expanded to its full size in memory.

To work out the minimum memory you need, you must first calculate the size of your largest image using the preceding formula. You need as a minimum enough memory to:

  1. Load an image editing program (32Mb including operating system)
  2. Open an image to manipulate (size of largest image)
  3. Open a second image or create a mask for use in a transformation (size of largest image)
  4. Create an output image (size of largest image)

 32Mb + 3 * [Largest image size] = Minimum Memory

How can I tell if I have too little memory?

Computer systems use a technique called virtual memory to extend the physical memory installed in your PC. Virtual memory create a memory overflow area on disk in a swap file. This technique enables you to run more programs at once on your PC than actually would fit in the installed memory.

It works because not all of these programs want to run at once, and even for active programs they do not access all the memory locations they have allocated to them. If however you run something like a graphics editor where all the images you want to manipulate at once won’t fit into memory then suddenly the PC is having to continuously swap memory back and forward from disk.

In really bad situations the PC will put out a block of memory to disk and then a few milliseconds later have to retrieve this same block again. This condition is called thrashing with the PC doing little else but reading and writing memory to disk.

You know you have too little memory when you get severe performance degradation and your hard disk is being continuously accessed.

Digital Photography Suitability

Should I still print all my images?

Trying to treat digital photography the same as conventional photography is doomed to disappointment. Image prints either at home or in photographic laboratories are simply too expensive.

Most of the images from digital cameras will stay digital for their entire lifespan. Born of a digital camera, growing up on a PC, spending their old age on a cd-rom and occasionally being reassembled from bits onto a PC display.

It is common now for PC displays to support true color and be capable of providing photographic quality rendition of images that look really good on 17″ and 19″ screens.

Well if we don’t generally print our images any more how do we share them?

The electronic world is providing more and more options every day. We have:

  • email, direct distribution of your photos to those most interested.
  • free web sites where you can upload your photos and tell your friends about them
  • personal web sites

What the Internet gains in speed of distribution it loses in quality. The image has to be practically destroyed with size reductions and JPG compression to get it down to around 20Kb for transmission over the Internet.

It does have its place. It is a great way to share images quickly with people who have no long term interest in the shots. Its a bit like passing the photographs around the office after you get them back from the processing lab.

It is inadequate where you want to share quality ‘prints’.

How do I share quality prints?

The paper print replacement of the electronic era has to be the cd-rom. The cd-rom can contain over 1,000 quality JPG images at a production cost of a couple of dollars.

What do I do with my thousands of images?

Digital cameras with no direct processing costs, immediate image previews and low image storage space are going to increase the number of photos we take and keep several times over.

What do we do with all those images? The production cycle is something like:

  1. Photograph is taken
  2. Preview checked for framing, exposure and general quality. If not adequate then back to step 1
  3. Image transferred to computer
  4. Image manipulated in image editor until satisfied. This may result in the production of one or more offspring
  5. Master image and offspring archived to cd-rom

Somewhere in this process there has to be included a method of finding an image again, a method of viewing selected images only.

Our opinion at CyWarp is that a cataloging program must be used to describe the images, record their location and to retrieve them. Accordingly we have produced the CyPics program to do precisely this.

There is an issue with offspring and tying them back to the original master. Our image cataloging FAQ suggests one simple alternative.