Task: Sentiment_Analysis

system
You are a helpful assistant. The assistant first thinks about the reasoning process in the mind by using Belief-Desire-Intention (BDI) framework and then provides the user with the answer. The reasoning process and answer are enclosed within <think> </think> and <answer> </answer> tags, respectively. 
Below is an instruction that describes a task. After thinking, when you finally reach a conclusion based on the customer's intention, desire and belief, clearly state the BDI thinking process within <think> </think> and then the answer within <answer> </answer> tags.


user 
Instruction: Determine the sentiment expressed by the user in her review from the provided choices, and respond by selecting one of the available options.

Input:
User Review: All in all, I am very happy with this lens.

I own a Nikon D40x, and up to now I've shot with the kit 18-55mm, the Nikon 50mm f1.8, and Nikon's 55-200mm.  I've been getting more and more into nature photography, and the limits of the 55-200 were annoying me, both in terms of auto focus speed and zoom.  I thought long and hard about what to do, though.  The 70-300mm is an obvious choice, but I also thought I might want to put my money into Nikon's legendary 18-200mm.  I figured that 300mm isn't really sufficient for nature (specifically bird) photography anyway, so maybe I should wait and save (for years, probably) until I can afford a $1k+ 2.8 telephoto.

Obviously, I eventually decided to go for the 70-300mm.  I did so because reviews are generally positive and because in the field of choices, it was the only telephoto lens I could afford that really made sense.  There are lenses from Tamron and Sigma that reach this focal length, but the usually lack either an internal focus motor (which I need on my D40x) or VR (which I personally need because I usually shoot without a tripod).  One thing that I was also ecited about was simply owning a lens from a class above the 18-55mm and 55-200mm lenses, which the 70-300mm lens is.

The 70-300mm exceeds the 55-200mm in more ways than the obvious increase in focal length.  Images are remarkably sharper and colorful through this lens.  It's a subtle thing, but I'm much more often impressed by the saturation and contrast of the photos I get from the 70-300mm than I ever was with the 55-200mm (This may be in part because the 70-300mm is corrected for 35mm cameras, whereas my D40x has a sensor smaller than 35mm.  Because of this, some of the outer portion of the lens, where optical problems are more common, are outside of the my camera's frame).  I would be pained to go back.

Using this lens is also much more pleasurable than using the 55-200mm.  The build quality feels much more solid and rugged, the focus ring is a true grip ring and not the dinky thing on the end of the 55-200mm's barrel.  The lens does not creep, which is nice for me because I like to go out romping on foot with the camera strap over my shoulder.  The lens stays put.

Autofocus is really fast compared to the 55-200mm.  A faster lens would do better, but for the amount of light that this lens takes in, it does a stellar job.  It's also quieter than the 55-200mm.

One difficulty I have had with this lens in comparison to the 55-200mm is that it is much heavier.  It's not uncomfortable to walk around with, but hand held shots are a little more unsteady for me due to this extra weight.  My arms will get used to it in time. :)

So, if you are looking for a solid telephoto lens that is relatively affordable but still a step up from the bargain 55-200mm lens, this is a great choice.  If I had bought a Sigma or Tamron I would probably be feeling some remorse about giving up on the great build and features of this lens.  If I had bought the 18-200 I'm sure I would appreciate the do-almost-anything convenience of it, but I would have spend even more money than I did on the 70-300mm for the same focal length range I already had in my two kit lenses.

One last thing to mention is the speed of this lens.  It's not super fast by any means.  I have to actively think about light levels and ISO in a way that I might not if I had a faster lens.  But of course this is good practice anyway.  I miss some shots because of low light, but this is really just a matter of how much money I can afford to spend on a lens.  I wouldn't fault this one for not being a 2.8.

Ideally, I would have the 18-200mm lens and a really nice 2.8 telephoto at 400+mm, but until the day that I have that kind of money, I'm very happy with the 70-300mm.

Options:
A: very positive
B: positive
C: neutral
D: negative
E: very negative


assistant
Answer: B: positive