Some noise at 100% magnification is normal with digital cameras, including the Canon 650D. Viewing at 1:1 is very demanding, so images can look noisier there than they do at normal display sizes.

Your lenses and tripod are not the cause; noise comes primarily from the sensor and exposure. The biggest factor is light: noise is most visible in darker areas and in underexposed images, especially if you brighten shadows later. ISO 100 helps, but it does not eliminate noise if parts of the image don’t receive enough light.

What to do:

• Expose accurately; avoid underexposure and heavy shadow lifting.
• Expect some noise when pixel-peeping at 100%.
• Apply noise reduction only as needed, especially in shadow areas.
• Be conservative: too much luminance noise reduction can smear fine detail.

There is no single slider value that works for every image. The right amount depends on the subject, exposure, and how much noise is actually visible in important areas. If noise is not visible at normal viewing size, it may already be acceptable. For stock, inspectors do zoom in, but they also care about preserved detail, so aim for a balance rather than trying to remove every trace of noise.