[Zeiss_T]

請教下各 Canon Fans
何謂 USM 呢?
係咪一個靜音 Motor?
同相片 Sharpness 有關嗎?
Thanks

[enos]

USM=Ultra Sonic Motor (for AF)

[i-Lens]

Canon Lens上解 UltraSonic Motor
Photoshop上解 UnSharp Mask

[kingkonghk]

uncountable SM, 即係玩過SM無數次咁多, 同SMS差唔多意思, SMS即係2次或更多SM, 有冇睇過SM片?

[man1492]

"係咪一個靜音 Motor? "

Yes, high speed quiet motor


"同相片 Sharpness 有關嗎?"

No direct relationship, it enables faster AF.

[Zeiss_T]

Thanks 各師兄解答
因為早日在 Dxhome 上, 有位 Canon 用家話想相片 Sharp D, 就開 USM ??????????
所以特此想搞清楚 "USM 同相片 Sharpness 的關係
Thanks alot

[insane]

USM = unsharp mask

It is a way to sharpen the image using software such as photoshop, photoimage. It works on increasing the contrast between neighboring pixels, giving you an impression that the image is sharper than it really is.

Most of the scanned photos need this process for them to look good on screen. Same goes for digital images by DC and DSLR. In the case of DC and DSLR, you have the option of turning on the sharpening function in the camera thru sharpness setting. Many however prefer to do the sharpening on computer since it gives you more control.

Overshapened images using USM will give you halo effect (an undesirable effect with a whitened ring around the sharpened edges). So go easy on this treatment.

[insane]

Just forgot to mention:

USM also stands for ultrasonic motor. This is a differnt way of driving the focusing ring on you AF lens. It has the advantages of giving you faster focusing speed with no motorised noise. But it DOES NOT make your image sharper. For this reason, the earlier reference to USM should mean "unsharp mask" in this case.

Hope the above helps.