簡單來說，相機幀率不僅受曝光時間的影響，因為幀率中還包含的有快門復位（消影）、幀讀取等額外時間
Hamamatsu Learning Center: Digital Camera Readout and Frame Rates (fsu.edu)
Frame Rate (fps) = 1 / (Frame Acquisition Time + Frame Read Time)
Frame acquisition time components:
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Time required to clear charge from the parallel register(並行寄存器) prior to beginning integration.
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Shutter opening delay in CCDs employing mechanical shutters.
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Exposure time.
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Shutter closing delay, if any.
Frame read time components:
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Time required to clear charge from the serial register prior to beginning readout.
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Time required for a parallel row shift times the number of rows in the array.
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Serial discard time multiplied by the number of pixels not intended to be read.
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Serial conversion (digitization) time per pixel times the number of pixels to be read.
Frame Acquisition Time = (TPR × Nclear) + Topen + Texp + Tclose
where T(PR) and N(clear) are the time required to clear the parallel register and number of clear cycles performed, and T(open), T(exp), and T(close) represent the shutter opening delay time, the exposure time, and the shutter closing delay time, respectively.
Frame Read Time = TSR + (Trow × Nrow) + (TSD × Ndiscard) + (tread × Nread)
where T(SR) represents the time required to clear the serial register, T(row) and N(row) are the time required for a parallel row shift and the number of rows in the array, T(SD) and N(discard) are the serial discard time and the number of pixels not being read, t(read) is the serial conversion time per pixel and N(read) represents the number of pixels to be read. This latter number is, at maximum, the total pixel array size, and is reduced in accordance with subarray readout and/or pixel binning operations.
由於這些 CCD 設計包括一個感光傳感器區域和一個遮光存儲區域，用於將幀傳輸到串行寄存器，因此曝光和讀出兩個過程可以在時間上重疊。相機系統可以提供可選擇的曝光和讀出模式，根據這兩種操作是按順序獨立執行還是同時執行分為非重疊和重疊模式。無論曝光時間如何，高靈敏度操作通常都需要非重疊操作。
非重疊模式：
當 CCD 在非重疊模式下運行時，可以指定任何曝光時間並完全完成，並在曝光結束時依次讀取。圖 4 顯示了說明這種曝光讀出模式的時序圖。在非重疊模式下，對序列中的每一幀重復相同的循環； CCD清除殘留電荷，在規定的曝光時間內對電荷進行積分，電荷從感光陣列轉移到掩蔽存儲陣列（分離存儲部分或行間陣列），最后讀出電荷。根據具體情況，曝光時間可能比讀取時間更短或更長，每幀的總時間為兩個間隔的總和（在沒有機械快門延遲的情況下），因為清除時間和移位所需的時間到存儲陣列的數據非常快，並且在確定幀速率方面並不重要。這種操作模式提供了與傳統全幀設備架構相似的性能。時序圖（圖 4）說明了一系列三個圖像幀的曝光和讀出時間序列。使用示例中顯示的任意時間，10 毫秒 (ms) 曝光和 50 毫秒幀讀取時間，獲取三幀的總時間為 180 毫秒（3 x 10 ms + 3 x 50 ms）。因此相應的幀速率為每秒 16.7 幀（3 幀/0.180 秒）。
相機重疊模式(overlap)下的兩種曝光情況：
重疊模式用於需要記錄動態過程的應用，其中需要連續成像以提供足夠的時間分辨率。為了最大限度地增加用於數據收集的時間比例，CCD 會連續運行（100% 占空比）。初始曝光后，數據被轉移到幀傳輸陣列，下一次曝光間隔立即開始，同時讀取前一幀。
該序列繼續時，幀到幀的時序由曝光時間或幀讀取時間決定，取決於哪個更長。因此，最小曝光時間等於幀讀取時間。在編程曝光時間小於讀出時間的情況下，序列中的第一幀按照編程的確切時間曝光，隨后的幀按照讀出時間曝光。序列時序實際上由較長持續時間的讀出周期控制。圖 5 顯示了重疊模式操作的時序圖，其中編程曝光時間為 10 毫秒，CCD 讀出時間為 50 毫秒，如前一個（非重疊模式；圖 4）示例中所使用。在此模式下獲取 3 幀所需的總時間為 160 毫秒，根據一次 10 毫秒曝光和兩次 50 毫秒曝光計算，這三個讀取周期重疊，每次 50 毫秒（10 毫秒 + 3 x 50小姐）。在重疊模式下運行會導致三幀序列的時間減少 20 毫秒，相應的幀速率為每秒 18.8 幀（3 幀/0.160 秒）。在這種類型的序列中，第一幀的曝光時間比后續幀短，並且圖像強度通常不匹配。
When the programmed exposure time is less than the frame read time, the following general expression can be used to calculate the total time required to capture a specified number of frames (N):
TN = (Tread × N) + Texp
where T(N) is the total time required to capture a sequence of N frames, T(read) is the single-frame read time, and T(exp) represents the programmed exposure time.
A second possible timing variation occurs during operation in overlap mode when exposure time is greater than frame read time, and therefore controls the timing of sequential frames. As a result, each frame in a sequence is exposed for the exact time specified in the system control software, and all images are of equal intensity. As illustrated by the timing diagram for this operation mode (Figure 6), after the initial frame of a sequence is exposed, readout takes place during exposure of the each subsequent frame, and the sequence ends with a final readout-only cycle. The timing diagram illustrated is for three frames exposed for 75 milliseconds each, and a CCD frame read time of 50 milliseconds. The sequence of three frames requires 275 milliseconds, calculated as three exposure intervals and one additional readout cycle (3 x 75 ms + 50 ms), and results in a frame rate of 10.9 frames per second (3 frames/0.275 second).
The following equation is utilized to calculate the sequence capture time for N frames in overlap mode when the programmed exposure time is greater than the frame read time:
TN = (Texp × N) + Tread
where T(N) is the total time required to capture a sequence of N frames, T(exp) represents the programmed exposure time, and T(read) is the single-frame read time.
