HINTS AND TIPS FOR OFOTO VERSION 2 (UPDATE 2.0.3) 10/14/93
This file contains hints and tips about using Ofoto Version 2 to optimize performance and ensure the quality of your images. Some of this is covered in more detail in the Ofoto User Manual, but this file contains some additional information. In either case, you should become familiar with the topics covered here as these supersede the documentation.
MEMORY PARTITION
• Memory partition in Ofoto: The minimum memory partition size for Ofoto 2.0 is 1536K. Optimal performance is achieved when Ofoto’s memory partition is approximately three times the size of the scanned image (as shown in the Selection Controls). For example, if a color image occupies 1.2 Mb, Ofoto will work best when the partition size is set to 3.6 Mb or more. (See page 103 of the User Manual to change the memory allocation.)
• Memory partition in other applications: Many applications need larger memory partitions to import or paste color images. Because of the large memory demands, use the Paste command only if the application has no alternative method, such as File Open. If you get an error message when importing or pasting, quit the application and, while the application is selected choose Get Info from the File menu. Increase the Current Size by one megabyte or more, then open the application and try again.
• Cutting, copying, and pasting: To use the Cut, Copy, and Paste commands successfully Ofoto must have enough memory reserved. The amount of space available for cutting, copying, or pasting is Ofoto’s reserved memory minus 1000K. To approximate the amount of space needed for a Cut or Copy, multiply by 2.5 the size of the selection (in kilobytes as displayed in the Selection Controls). If the amount of memory needed is greater than the amount available, you will need to increase the memory partition.
HINTS FOR SPEEDING UP SCANNING
As with any program, there is always a tradeoff between performance (the speed of the program) and the quality of your results. Here are a few ways you can optimize the performance while controlling quality.
• Avoid unnecessarily high resolution: Ofoto’s default dpi settings are designed to match the capabilities of your printer. Using the expert controls to manually override these defaults to scan at a higher resolution will slow down scanning, saving, and printing of images, and will generally not improve your results.
• Turning off Moiré Removal: With some scanners, the additional image processing invoked by Ofoto’s Moiré Removal feature can slow down scanning considerably. If you find scanning of photographs to be extremely slow, make sure the Moiré Removal option (in the Options menu) is unchecked. However, for the best possible quality, turn Moiré Removal on as it can clean up subtle artifacts that can sometimes be seen in scanned photographs as well as the more obvious moiré patterns that appear when scanning pre-screened originals.
• To shorten a Prescan or Autoscan: During the preview scan phase of a Prescan or Autoscan sequence, hold down the Option key until the Stop button changes to read “Continue”. When you see that the preview scan has scanned as much of the image as you want, click the Continue button. Ofoto interrupts the preview scan at that point and continues with the next phase of the Prescan or Autoscan sequence.
• To shorten launch time: When you open Ofoto, the program loads all calibrations, including built-in calibrations and any additional calibrations that you have created. To shorten the time it takes to open the application, delete calibrations you don’t need. (See pages 146–147 in the User Manual to delete a calibration.)
SCANNING WITH THREE-PASS COLOR SCANNERS
Prescan and Autoscan can be very slow with three-pass scanners as Ofoto has to wait for the scanner to make three passes over the image just to perform a preview scan and identify the image type. You can speed things up dramatically by turning off Autodetect and controlling the Prescan phase manually, as follows:
• Prescanning manually in grayscale: First, choose Image Type Controls from the Options menu, and select Grayscale Photo (see page 106). Click Prescan to get a preview scan. Select the part of the image you want to scan. Choose Color Photo (if it’s a color photograph) in the Scan Controls. Click Scan.
• Using the Continue button: If you click the Continue button during the Prescan (by holding the Option key down as described on page 43), Ofoto interrupts the Prescan at that point and then goes on with the next scanner pass. In this way you can limit the three passes of the scanner to the upper portion of the platen.
• Using the Stop button: If you click the Stop button during a Prescan, Ofoto does not continue with the remaining scanner passes. However, Ofoto does not perform any Auto Highlight/Shadow correction or Autodetection of the image type (if these features are enabled). Nevertheless, you can manually set the image type, select the region you are interested in, and click Scan to rescan the image. You can then adjust Highlight and Shadow values manually. (See page 81 of the manual).
DISPLAYING IMAGES
To understand how the appearance of your images on your monitor relates to how they will actually print, you should know whether you are viewing the images in 24-bit color, 8-bit (256 colors), 4-bit (16 colors), or 1-bit (black-and-white) mode.
• Determining or setting your monitor mode: Choose Control Panels from the Apple menu, then click the Monitors control panel. Near the top of the control panel is a list of the possible gray levels or colors available on your monitor. If the highest value is “Black & White” you have a 1-bit monitor; “16” for a 4-bit monitor; “256” for an 8-bit monitor, and “Millions” for a 24-bit full-color monitor. Usually, this is set to the maximum value but some people set it lower (e.g. to give up display quality to speed up redraw).
• Appearance: Full-color images may not display well on 8-bit, 4-bit, or 1-bit monitors, but should print correctly. The same holds for grayscale images on 4-bit or 1-bit monitors.
• Seeing the effects of color corrections: When your monitor is in “256 Colors” or “16 Colors” mode, and you are working on a color image, you will not see any animation of color change operations. The Preview checkbox on the Color Correction and Highlight/Shadow dialogs and the sliders on the Brightness/Contrast dialog have no effect on the displayed image until you click OK.
• Color correction swatches: As mentioned on page 87 of the manual, when Preview is checked in the Correct Color dialog box, all the colors on the monitor are changed to show the effect of the correction specified in the two swatches. This includes the colors in the swatches themselves (if they are on the same monitor as the image). If this is confusing, and you want the swatches to display the actual colors you select, turn off Preview.
• Using the eyedropper: Any colors you sample from the image with the Eyedropper may not be displayed accurately when your monitor is in “256 Colors” mode. Many colors that look identical on your monitor may actually be quite different. The same holds for gray values sampled from a grayscale image while your monitor is in “16 Grays” mode.
• Monitor calibrations and black-and-white monitors: You should not adjust the Gamma slider in the Monitors Calibration dialog box if your monitor is in “Black & White” (1-bit) mode. The slider will have no apparent effect on the bar above the slider. On a 68000 Macintosh, the bar will appear to be missing altogether.
• Using other monitor calibration systems: If you are using another company's monitor calibration system or system-wide gamma tool to linearize your monitor, you should select RawMonitor in the Ofoto Preferences dialog. This makes sure that Ofoto does not apply any correction to the displayed image.
COLOR FILE FORMATS AND CALIBRATIONS
Every file format and calibration that is used for color images is either CMYK or RGB. (If you are not familiar with the distinction between CMYK and RGB, see the Glossary and page 109 in the User Manual.) In general, you will get better color results if you use a CMYK calibration when scanning, and a CMYK file format to save images. This provides Ofoto with greater control over the color separation process by allowing Ofoto to perform the RGB to CMYK conversion. (See page 114 and 141 of the manual.)
• Picking a file format: Deciding whether or not you can use a CMYK file format, and which one to use, depends not only on the application you are importing an image into, but also what software, printer driver, and printer you are using to print. Since the combinations can be endless, ask your service bureau what file formats you can use, or check the documentation that comes with your application(s) and printer. Always test a file format to make sure that it both imports and prints properly from your application(s) before scanning and saving a number of images using it.
• DCS and applications: Some applications can appear to support DCS in that they can import the DCS master file and may even print it successfully to a color printer. However, the image printed will be the low-resolution preview in the master file, not the composite of the high-resolution C, M, Y and K channels. A separation utility or extension may be required to print the image properly. Check the documentation for your printing application(s) to determine the procedures that apply to using DCS-type separation files.
• DCS files should never be renamed: An image saved as DCS is actually saved as five EPS images — a master file and four files suffixed with either C, M, Y, or K (the color “plate” files). These four files must not be renamed or else your application will be unable to find them. Also, while it’s usually easiest to keep all files together, some applications will present a dialog advising you if the plate files cannot be found, and giving you an opportunity to locate them through a standard file Open dialog at print time. [NOTE: A pending revision to the DCS specification will eliminate the multiple file approach taken by the current implementation of DCS, making the use of DCS separations less cumbersome.]
• EPS CMYK: The EPS CMYK file format is also supported by Ofoto Version 2. It is similar to DCS in that it is based on Encapsulated PostScript (EPS), but it differs in that it holds the composite CMYK image in a single file, instead of five EPS files.
• CMYK and RGB calibrations: Every color calibration is either a CMYK or an RGB calibration, depending on whether it was created with a color chart saved in a CMYK or an RGB file format. If you scan with a CMYK calibration, you should use a CMYK file format when you save the image. Ofoto will warn you if the calibration and file format are incompatible. In general, all you have to remember is that you should calibrate your print pipeline (which includes the file format you will use to save images) and print your images in the same way that you calibrated.
• Built-in color calibrations: Most of Ofoto’s built-in color calibrations are CMYK calibrations. The exceptions are the Apple Color Printer and the SuperMatch ProofPositive. These are QuickDraw printers (as opposed to PostScript printers) and the QuickDraw interface only allows RGB color.
CLIPPING OF CALIBRATION CHARTS
When printing a calibration chart, it is important that the entire chart is printed. A slightly clipped chart can result in a bad calibration and poor images.
• Many printers have a printable area smaller than a full sheet of paper. For example, a Tektronix Phaser™ IISD has a printable area on an 8.5x11-inch page that is actually only 8.1x8.6 inches. If part of a calibration chart extends into the unprintable area, it will be clipped. To avoid this, when placing a chart in another application, make sure that it is exactly centered on the page. (Ofoto automatically centers the chart if you are printing directly from Ofoto.)
• Many page-layout programs allow you to import graphics into a picture box or frame. When placing a calibration chart in a page-layout application, make sure that it is centered within a picture box or frame that is large enough to contain the entire chart.
To verify that the top of a chart has not been clipped, make sure that the black space above and below the word “OFOTO” is equal. On the other three sides of the chart, make sure the thin line around the perimeter is intact.
REOPENING AND RECALIBRATING OFOTO FILES
Although slight, there may be some degradation of image quality if you repeatedly reopen a calibrated Ofoto image. This is because the image must be “decalibrated” — converted back to Raw data — at the time the image is opened. If you just reopen the image once, the loss of quality will be unnoticeable, but reopening an image multiple times may introduce noticeable degradation.
There is no loss of quality if you open or import an Ofoto image into another application.
• Opening an Ofoto file in another application: If you use another application to open a calibrated image, save it again, and then reopen it in Ofoto Version 2, Ofoto may not be able to tell if it has been calibrated or not (as the information needed to “decalibrate” it may have been discarded by the other application.) It may see it as “Raw” even though the data has actually been calibrated. This is not a problem — as long as you don’t recalibrate (change the pop-up menu from “RawPrinter” to another calibration). If you do, Ofoto will calibrate data that has already been calibrated, and you may get unexpected results. (This is described on page 155 of the User Manual).
• Use “RawPrinter” (or a copy) if you plan to reopen an image in Ofoto: There is no loss of quality if you reopen an uncalibrated (Raw) image in Ofoto. Using “Raw” also allows you to edit an image in another application, and then reopen it in Ofoto without losing valuable calibration data.
• Creating a copy of RawPrinter: Use the Edit Calibration List dialog box to Duplicate and then Modify a copy of “RawPrinter” as an intermediate calibration for saving images you plan to reopen in Ofoto. For example if you plan to reopen an image and then print it on an Apple Color Printer, first create a Raw calibration for this purpose as follows:
1. Choose Edit Calibration List from the Calibrate menu.
2. Determine the maximum dpi you will need later to recalibrate. To do this, select the calibrations you plan to use later, note the Photo dpi value for each, and choose the highest of these. (For example the Apple Color Printer has a Photo dpi of 135.)
3. Select RawPrinter.
4. Click Duplicate and give the copy a name like “Raw 135 dpi”.
5. Click Modify and change the Photo dpi. (In this case we set it to 135 dpi). You can also change the Print bits to 8:G if the eventual printer is grayscale.
6. Click Done.
You now have a 135-dpi version of RawPrinter that you can use for saving images that you later plan to reopen and recalibrate for printing on the Apple Color Printer.
• Recalibrating an image: As described on pages 154-155, you can recalibrate an image without loss of quality as long as you don’t go *up* in dpi. For example, you can scan a photo using an imagesetter calibration, and then change to a laser printer calibration without rescanning. However, if you scan for a laser printer, and then change to an imagesetter calibration, you should rescan because you need to capture more data from the scanner. Ofoto will warn you with a “Rescan Recommended” message in the status bar.
To recalibrate, change the Calibration pull-down, and then choose Apply Scan Controls from the Image menu.
USING COLOR CALIBRATIONS WITH MORE THAN ONE SCANNER
If you scan with a different scanner model than was used to create a color calibration, Ofoto must do extra decalibrating and recalibrating to compensate for the different scanners — this will cause considerable slowdown when saving and reopening files, and slight degradation in image quality. This is a pretty rare situation (and Ofoto will warn you when this happens), but it can sometimes be an issue:
• Exporting calibrations between systems with different scanner models: If a color calibration is created on a system (for example at a Service Bureau) that has Scanner A, and you export it to a system with Scanner B, saving will be noticeably slower. Rather than exporting the calibration, use the original calibration chart (if possible), to create a new calibration with Scanner B.
• Reinstalling Ofoto with a new scanner: If you install Ofoto when Scanner A is attached to your system, and then replace it with Scanner B, you should remove (or rename if you want to keep a backup) the entire Ofoto Preferences folder, before reinstalling Ofoto. This ensures that all calibrations, both built-in and custom, will be appropriate for Scanner B.
• Reopening an Ofoto image created with a different scanner model: If you are running Ofoto on a system that has Scanner A attached, opening a calibrated color Ofoto image that was scanned with Scanner B will be considerably slower and may introduce a slight degradation in image quality. This might happen either because you’ve replaced the scanner on your system or because you’ve transferred an image to a system with a different scanner. If you must transfer images in this way, use a copy of RawPrinter as described above, and recalibrate with a calibration created with Scanner B.
