D7 100 has some problems, and sometimes the photography of various documents will be delayed.

You can't use it,

Aperture priority,

Shutter priority,

Full manual gearbox,

These three gears,

And I still don't understand the reason of these three gears.

You must set a reasonable aperture and shutter before pressing the shutter.

Aperture size, shutter speed, mutual matching, different matching methods, the same scene presents different effects,

Press the shutter when the shutter speed is low, which is naturally what you call delay. If you face the darkness, you may find that your camera will be delayed for a few minutes before taking pictures.

I want to explain it to you here. It takes a thousand words, which will probably make you dizzy.

I can only let you know here that there is nothing wrong with the machine, but you can't operate it.

You did confirm this first.

The rest, through learning, is not a problem.

This thing is very practical. I don't know how to read only words. I'm absolutely dizzy

You should learn to use these three gears one by one.

Generally, you should learn the aperture priority mode first, which is the basis of playing SLR (it is shameful not to always use automatic gear when playing SLR). When you get used to the aperture priority mode, you will naturally use those two modes when you stumble upon an opportunity.