Montage Setup Dialog

This dialog box allows you to set the parameters for a montage, see the total area to be acquired, and view the parameters after montaging has been initiated. When this dialog is invoked by the Navigator to set up a montage that fits a defined area, it operates in a special mode, referred to as area-fitting mode. In this mode, you can adjust the number of frames and overlap between frames by changing the magnification or a percentage overlap factor. When one of these settings (or the binning or the selection of stage versus image shift) is changed, the dialog will maintain the fit to the selected area by having the Navigator recompute the number and size of frames and their overlap.

Montages can also be taken in Low Dose mode, with either the Record or View area imaging parameters.  Whether a montage file can be acquired into in Low Dose depends solely on whether Low Dose was on when the montage was first set up.  Thus, you need to turn on Low Dose mode before setting up a montage to be taken in Low Dose.  Several parameters cannot be changed when in Low Dose mode.

Camera radio buttons

If you have multiple cameras, each available camera will be listed here so that you can specify or see what camera will be used for montaging. The current camera will be the one initially selected. If you select a different camera, it will become the current camera when a montage is started.  The camera selection is fixed in Low Dose mode.

Magnification

When not in Low Dose mode, this setting is initially based on the current microscope magnification, but you can change the magnification if desired using the spin buttons. SerialEM will automatically switch to this magnification whenever acquiring a montage. You can also change the magnification after montaging has been started, but you will have to confirm this change the first time you do so. In area-fitting mode, changing magnification will change the number of frames and may change their size and overlap.  In Low Dose mode, the magnification is simply that of the Record or View area and cannot be changed here.

Binning

This setting is initially based on the current value in the Record parameter set (or possibly the View set in Low Dose mode), but you can change the binning when setting up the montage. If you do so, the program will adjust the exposure time by the square of the change in binning, but you will also be warned to adjust the exposure and drift settling parameters yourself. If you have already started montaging, you may be able to change the binning if it is compatible with the size of the pieces. In area-fitting mode, changing the binning will cause the fit to be recomputed.

Pixel size

This value is based upon the magnification, the binning, and the calibrations in SerialEM.

Number of pieces in X and Y

You can set the number of frames of the montage in the X and Y directions by entering numbers in the text boxes or using the spin buttons. In area-fitting mode, changes here will be superseded if you change any of the settings that cause the fit to be recomputed.

Piece size in X and Y

You can set the size of each piece in X and Y by entering values in these text boxes. The default is the full size of the CCD camera. In area-fitting mode, changes here will be superseded if you change any of the settings that cause the fit to be recomputed.

Overlap in X and Y

You can set the amount of overlap between pieces by entering values in these text boxes. The default is 10% of the frame size of the CCD camera when doing a montage with image shift. When using stage movements, the overlaps are constrained by a minimum percentage and by a minimum absolute distance in microns. You can use the Reset button to restore the values to the 10% default for image shift or the minimum required for stage montages. These values may change when new piece sizes are entered.

In area-fitting mode, these fields are disabled and overlap is adjusted with the minimum overlap controls instead.

Minimum overlap factor (Montage with stage movement only)

These controls allow you to adjust the minimum amount of overlap required when doing a stage montage. At lower magnifications, a percentage is enough to guarantee enough overlap, but an absolute minimum amount of overlap is needed to get enough overlap at higher magnifications, because of the imprecision of stage movement. Use the spin buttons to adjust the minimum overlap between pieces as a percentage of the largest piece dimension, and enter a value in the text box to change the minimum overlap in microns. Overlaps will be increased to meet an increased minimum, but will not be decreased when you decrease a minimum until you press the Reset button.

In area-fitting mode, the overlap will change automatically not matter which direction the minimum is changed, and the number of frames may change to maintain the fit to the desired area.

Total area and Update

The total area is computed based on the pixel size, number of pieces, piece size and overlaps. It is recomputed whenever you push a button or leave a text box, but to be sure the value is current, just push the Update button.

Move Stage instead of Shifting Image

Select this option to have the montage acquired by moving the stage instead of using electronic image shift. Image shift is quite accurate but has a limited range at medium and high magnifications (generally less than ~15 microns, but less than ~3 microns on some microscopes such as 300 KV Tecnai/Polara). Stage shift can be used when these limits need to be exceeded. Note that in LM mode, image shift has a much higher range, so you may be able to use image shift instead of stage shift at the highest LM mode magnifications. In area-fitting mode, the fit will be recomputed and it may not be possible to change this setting.

Skip Pieces outside Navigator Item

With this option, it is possible to define a polygon in the Navigator and have each montage that is taken include only pieces that have some portion inside the polygon. This option is not needed when taking a montage that was fit to a polygon but would be useful when taking multiple montages in a region (e.g., supermontaging). After checking the option, enter the position of the desired polygon item in the Navigator table (numbered from 1), or enter 0 to use the current Navigator item or the polygon that was used to define the supermontage including the current item. In other words, the option is only needed when supermontaging, and the value just needs to be 0. The legality of the item number will not be checked until the montage is started. If the Navigator is not open at that time, this setting is ignored.

Do Full Rectangle; Ignore List of Pieces to Skip

When a montage is set up by the Navigator, it will compose a list of pieces that do not need to be acquired because they fall outside the polygon used to define the montage area. The option allows one to acquire the complete array of pieces, including ones on the list to skip.

Ask about Making Map after Each Montage

If this option is checked, then when you take a montage manually, the program will ask whether you want to make a Navigator map. It is available only when the Navigator is open. It is turned on when you set up a montage through the Navigator; otherwise it is off by default. If you answer with 'Cancel' by mistake when asked if you want to make a map, you can use this option to re-enable the offers to make a map.

Use continuous mode with settling factor

This option is enabled for Gatan cameras where continuous camera acquisition can be used through the SerialEMCCD plugin and allows a montage to be acquired by selecting from the stream of images taken in continuous mode.  It is most effective for OneView cameras, where drift correction can be used in continuous mode to produce good-quality images even if there is some residual drift in the images.  It could also be useful for taking good-quality montages with a K2 or Orius camera if the normal settling time after movement is used, or for taking maps with a reduced settling time.  The settling factor is a multiplier applied to the normal settling time that is allowed to elapse after an image or stage shift before starting a regular image acquisition.  In continuous mode, the program will allow the modified settling time to elapse before asking for the next image that comes from the camera.  You will need to experiment with this factor to determine what value gives adequate quality for your application.  Small values like 0.25 to 0.5, or even 0, may be acceptable with a OneView doing drift correction.

Turn off Drift Correction for stage montage

This option is enabled when a montage with stage movement is to be taken with a OneView camera.  If it is turned on, the Drift Correction setting can be left on in the Record parameters but the correction will not be used when taking images for the montage.  The reason this may be desirable is that the OneView discards frames that it fails to align, giving images with counts that are lower proportional to the number of lost frames.  This can easily happen when taking maps of areas that contain some empty regions.  The program keeps track of two settings of this option, one for regular and one for "high-quality" stage montages (described in the next section).  The initial defaults are to have the option off for high-quality montages and on for regular ones.

Use settings for high-quality stage montage

Use this option to activate a collection of settings that are relevant only when doing large stage montages for acquisition of data to be analyzed, as opposed to maps. These options appear when the box is checked:

Autofocus at each piece

Select this option to have the autofocus routine run before acquiring each piece. This will have no effect in Low Mag mode. Turn this on will turn off 'Autofocus in blocks', and vice versa.

Repeat until drift is below a limit

Select this option to have autofocus repeated if the drift, in nanometers per second, is above the limit that you enter in the text box.  The option is available only when autofocusing at each piece.  The program will repeat the autofocus up to five times if necessary, then go on to acquire the piece.  You must have the Drift Protection option in the focus menu selected for this operation to work.

Autofocus in blocks of pieces

Select this option to acquire the montage in square blocks of a size selectable with the spin button, and to have the autofocus routine run at the center of each block before starting the block. This option radically changes the order of piece acquisition. Without blocks, pieces are acquired in columns (along the Y axis of the camera). With blocks, a whole block is acquired (in columns just like a montage of that size), then the next block is acquired in Y, etc. After finishing a column of blocks, the program shifts over by the block size in X to start the next column.

Realign with image shift up to a limit

This option can be used to deal with several problems with stage montages: irregular movements that produce variable amounts of overlap; long-term drift that results in overlaps between very long columns being inadequate because a long interval passes between successive passes up the column; and even some inaccuracy in the stage calibration.  For every piece after the first one, the program picks an adjacent, already-acquired piece to align to, moves the stage to the target location of the piece to be acquired (based on the actual position at which the neighbor was acquired), autofocuses if that option is selected, then sets image shift in order to take an image that overlaps as much as possible with the one from the adjacent piece.  The amount to shift is limited by the number in the text box, in microns.  The image is aligned and image shift is then set to take a picture that is in exactly the right location relative to the neighbor. However, if the alignment shift is larger than the percentage indicated in the text box for Maximum alignment shift as % of piece, then it will be ignored.

This option cannot be used together with focusing in blocks.  Using image shift can be slow because of the settling time required after an image shift.  If you are doing extensive acquisition with this option, you should see if you can reduce this delay time using the procedure described for Set IS Delay Factor in the Calibrate menu.

With this option selected, the program will remind you to calibrate image shift for the current magnification, but only if the possible error in overlap caused by plausible errors in the current shift calibration is large enough.  Large amounts of image shift as a fraction of the frame size, and narrow overlap zones, will trigger this reminder.

Go from center out; anchor at lower mag

When using realignment with image shift, this option can be used to protect against the possibility of poor correlation alignments at the periphery of the area being acquired (e.g., due to grid bars or empty resin).  Pieces will be acquired from the center outward: for each column, the program starts in the middle of the column and goes down then up; columns are done from the center leftward, then from the center rightward.  In order to find the center again for the second half, an 'anchor' image will be taken at the magnification selected with the spinner and stored in a temporary file before the montage is started.  The program will also use this image to estimate the backlash occurring between the two directions of movement.  For reliable correlations, the image needs to have a field of view at least twice as big as the possible drift in stage position over the first half of the acquisition.  Initially, the program will try to pick a magnification that gives a field of view of at least 20 microns as long as that is not in low mag; thereafter it will remember your setting.  Be sure that images can be taken at the chosen magnification without the aperture occupying more than the corners of the image.

Delay time after moving stage

The value here sets the delay time between stage movement and the acquisition of an image. This delay may need to be longer than the default to give images without drift.  Currently, the default of 2 seconds (or whatever is set in the properties file with 'StageMoveDelay') will be applied as a minimum delay and a value here of less than the default is ignored.

Skip correlations used to align pieces

The correlations that are usually used to assess how well pieces align can consume a significant fraction of the acquisition time, especially when the option is checked in the Montage Control Panel to treat the montage as 'Very sloppy'. Use this option to disable the correlations. Note that correlations will not be done for montages with more than 200 pieces, regardless of this setting.