For far subject, I am planning to buy " Nikon AF-S DX NIKKOR 55-200MM
F/4-5.6G ED VR II " or 70-300. Here are my question:
- Will f/4-5.6 allow me to precisely control depth of the field? My 18-55 does decent job but I have to be very close to subject to get
more background blur effect.
- Is it wise decision to keep multiple lens when travelling abroad with limited luggage.
Okay let's learn a little about what shallow depth of field and great depth of field really are.
To keep it simple, the differences lay within the aperture. If you want to have an image that has a Bokuh style (blurry in the background, clear on the subject) then you need an aperture that with a wide pinhole. Meaning, the larger the pinhole the blurrier the image can be. In reverse, the lower the f/stop, lets say f/22, then the image - if focused right - will be considered Great Depth of Field or infinity depending on the type of lens you use. Older SLR lenses would refer to it as infinity which was in relation to the focal distance.
My guess is, since you're a newer photographer you won't be getting up into peoples faces with a 20-35mm lens taking portraits. That takes some balls and experience.
Now, unless you are using a lens that has image stabilization on it and you are shooting with a 300mm lens you will need a shutter speed of 1/320 roughly in order to prevent shaking. The longer the focal lens, the higher susceptibility to shake. Therefore, a higher shutter speed is needed to compensate for the shake. Now, what does that mean? A high shutter speed? Well, that means your image will come out dark if you left it with an ISO of 100-(clearest) and an aperture of f/4 (which is what you seem to want). Which means you will have to open your aperture up to let in more light - reducing the depth of field and you will need to increase your ISO - reducing your clarity (increase noise).
On a lens, it may say f/1.2-f/5.6. But what does that mean? That is the LOWEST possible f/stop reading the lens can handle. It doesn't mean that is the highest f/stop.
If you are shooting in full auto, you need not be concerned with these topics, but then if you are I question why you bought a $500 camera. That is besides the point.
Question 1: Nothing will change. Yes, at 300mm you can be further away to get the blur effect.
Question 2: It depends if you have a way to securely keep them safe and protected. Do you keep the mount caps? Restrict their movement. Keep the lenses with you on the plane while flying as a carry on. You will need to make sacrifices to what you can bring if you are bringing a camera with limited luggage.
Here is my flicker so you can see the metadata. Look closely.