除了儀器表現與分析者的影響外，研究者也應考量兩儀器的使 用限制，兩者共同的限制為天氣狀況，兩種儀器乃偵測光線的差異 或是根據影像分辨孔隙，需要合適的天空背景才能有效偵測光線差 異或分辨天空與葉片，因此有直射光的天空背景容易影響林下與林 外的光線差異之偵測，或使葉片的邊緣模糊消失，導致儀器無法測 得，進而影響量測結果。
此外，植冠分析儀需於林外與林內各設一組儀器，但多數研究 地點並沒有足夠的開闊地或突出樹冠層的高處等可設置林外儀器，
因此需於鄰近地區找尋空曠處或高處放置。但天空狀況可能在相鄰 兩地就有很大的不同，很難確保兩組儀器所在地的天空狀況是相同 的。且無法立刻得知所記錄的資料是否完好，也無法記錄影像。半 球面影像則不須顧慮林外儀器的問題，拍攝者自身即可確認天空狀 態是否適合半球面影像記錄。且現代的數位相機可即時觀看拍攝之 影像，當下便可確認影像資料是否適合分析，不必像植冠分析儀需 接上專用的軟體後才能得知資料狀況。
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擇儀器與分析、比較、解釋儀器間的結果時須特別注意。研究者除 了以儀器表現做為選擇依據外，應適當考量兩種儀器實際在野外操 作、分析時可能遭遇到的困難來選擇適合研究的儀器與分析方式。
本研究的趨勢檢驗多為儀器間相互比較或使用前人研究中相同 或類似地點的直接研究結果作為參考值，缺乏同時間同地點的直接 量測值佐證，但使用直接量測法的困難點在於僅限一次性的測量葉 面積，因此若要使用直接量測法之結果佐證儀器於同種森林內的量 測趨勢相當困難，建議未來的研究者可以朝這方面努力，以直接量 測法驗證儀器呈現葉面積變化趨勢的表現如何。
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