[HP_HKG]

F1.8; F2.0 and F2.8等光圏值可以在各款數碼相機中見到，但想問問實際上有何重大分別呢？

光圏值越大；光線量越多；景深便越大；物件的前後位置便越明顯，但實際上當F1.8與F2.8相比，景深的多少程度是否有很明顯的分別呢？

本人以肉眼比較過兩者，覺得沒有明顯的分別，這是否要視乎拍攝的影像是什麼才可比較這兩個光圏值所造成的分別？

請攝影專業人士回答。

[Himalayan]

Not only F光圏值 affect 景深, are you also comparing with same Focal Length? (e.g. 50mm?)

[HP_HKG]

While keeping other variables such as Focal Length (35mm) constant, different aperture values (F1.8 and F2.8) have not found to produce significant effect in image depth (景深) in my eyes...

這是否要看看其他因素？

[Philippe]

要看數碼相機的感光完件大小,太小的話光圈對景深影響不太明顯

[HP_HKG]

Take examples of Nikon COOLPIX 5400; Canon PowerShot G5 and Olympus C-5050Z, in which the ranges of aperture values are varying...

I would like to enquire about which one is better in terms of its aperture value that can bring about good image quality by image depth in naked eyes...

I know that the CCD sensors used in these three digital camera models might be different among themselves, which can contribute to the different resultant image quality...

[Philippe]

三部都係用1/1.8"CCD,C-5050Z的光圈較大,做淺景深較有利.

[HP_HKG]

Yes, Olympus C-5050Z is I believe the best among others in the same class in producing good image quality by its largest aperture value.

Do you mean "deep" image depth by large aperture value; "shallow" image depth by small aperture value?

[tam_dominic]

F8 gives large range of sharp area ie deep depth of field
eg When you focus at 10 feet, sharp area is from 5 feet to 20 feet

F1.8 gives small range of sharp area ie shallow depth of field
eg When you focus at 10 feet, sharp area is from 9 feet to 13 feet

F1.8 is large aperture
F8 is small aperture
ie. The small number the larger aperture (the hole inside the lens)

Usually good image of a specific lens is from 2 to 3 F stop smaller then the largest aperture. eg Assume F1.8 is the largest aperture, then about F4 produces the best image quality. This all depends on the characteristic of the design of the lens.

Happy shooting !