Task: Sentiment_Analysis



 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.  /nFor the BDI reasoning process, (1) Based on the User Review, starting with "customer believes", list the user's beliefs; then, based on the User Review and the definition of Reiss's 16 basic desires theory, list the user's desires; next, based on the listed beliefs, desires and User Review, starting with "customer intends", list the intentions; (2) Finally, based on the generated beliefs, desires and intentions, construct logically BDI reasoning process, and select the correct answer based on the BDI reasoning process and input. /nThe definition of Reiss's 16 Basic Desires Theory: 1. Acceptance - the need to be appreciated 2. Curiosity, the need to gain knowledge 3. Eating, the need for food 4. Family, the need to take care of one’s offspring 5. Honor, the need to be faithful to the customary values of an individual’s ethnic group, family or clan 6. Idealism, the need for social justice 7. Independence, the need to be distinct and self-reliant 8. Order, the need for prepared, established, and conventional environments 9. Physical activity, the need for work out of the body 10. Power, the need for control of will 11. Romance, the need for mating or sex 12. Saving, the need to accumulate something 13. Social contact, the need for relationship with others 14. Social status, the need for social significance 15. Tranquility, the need to be secure and protected 16. Vengeance, the need to strike back against another person/nNow the user gives an instruction that describes a task and ask you write a response that appropriately completes the request. After thinking, when you finally reach a conclusion, clearly state the BDI thinking process within <think> </think> firstly and then the answer (i.e., answer only letters in options) within <answer> </answer> tags.
Instruction: Analyze the user's review text and determine the overall sentiment expressed, then choose the corresponding sentiment option from the provided list (A: very positive, B: positive, C: neutral, D: negative, E: very negative) based on the identified sentiment.

Input:
User Review: Nikon released its 1.4G "update" of the 1.4D a few years ago.  If you look at the Amazon.com reviews of that lenses, you might think that it was a major improvement over the 1.4D.

It was not.

The obvious benefit of the G is that it provides autofocus on Nikon cameras that don't have "screw-drive" motors built in.  Autofocusing requires a motor to physically move the lens elements into the proper position to produce a focused image.  This motor can be built into the camera or the lens.  Older Nikon cameras and enthusiast-pro level cameras have AF motors.  Consumer-grade cameras (e.g. D40, D3000-D5100) do not. Therefore, Nikon needed to produce a "standard" (50mm) lens for these consumers. Nikon has subsequently introduced,  in its G-range of prime lenses, 35mm f/1.8 (with a 52.5mm equivalent FOV, close to standard on DX), 60mm f/2.8, 85mm f/3.5 and 105mm f/2.8. Recently, Nikon announced a 50mm 1.8G, which gives another option to consider.  All of these lenses will autofocus on any and all of Nikon's DSLR cameras.

So what other benefits does the 50mm f/1.4G offer over the older D model?

Some claim that the G has better AF accuracy than the D.  I don't know, since I don't shoot action photography with the 50mm.  I do know that my keeper rate is no lower than any of my other lenses including the 35mm 1.8G.  However, one thing that is clear is that the G focuses much slower than the D (see the review on slrgear.com).  In their tests, the G is over 60% slower focusing than the D focuses on the D90. Compared to a D on a D700, the G is 150% slower. Notice that focus speed with a screw-drive lens depends on the speed of the camera motor.  The D90 has the slowest motor, but is still substantially faster focusing the D than the G focuses on any camera.

As for IQ, most of the review sites find little difference between the two lenses. The G is better at some apertures, the D is better at others, and both are weak at 1.4 (most reviews give a slight nod to the G at 1.4). Personally, I rarely use this lens.  I typically gravitate towards the 35mm for general use (it gives me the traditional standard FOV), and I put on my 85mm for portrait shots. However, I am amazed when I look through my photos at how sharp and contrasty my 50mm D shots are.  I sometimes have to take a second look to confirm that they are 50mm shots and not 35mm shots.  Thus, there isn't enough of an IQ difference to move up to the G. Given the G's slow focusing, you might miss a few shots that you would have gotten with the D.

50mm lenses are truly capable of taking wonderful shots.  Given the slight price premium (~$200) over the 1.8, I would pick the 1.4. In a pinch, you will get decent results at f/1.4 and f/1.6.  Your results may not be magazine-grade at these wide-open apertures, but they will be as good or better than most shots you take with a kit lens (any of the 18-XXX lenses).  Some of those kit lenses produce extremely sharp results.  But they are lacking in color and contrast.  The 50mm loses contrast wide open, but the color stays strong.  More importantly, you have shots at 1.4 and 1.6.  Is it worth the $200 premium?  Considering that you get to play with up to 60% more light it is in my opinion worth the premium if you can afford it.  Remember that Nikon charges over $1500 to step up from 1.8 to 1.4 in its 85mm range, so the $200 premium is an incredible bargain.

So, if you are on an extremely limited budget and have a D80 or higher end camera, get the 1.8D.  The extra speed is nice, but not essential.  If you can afford it, and are enthusiastic about photography and have a camera that can drive it, get the 1.4D.  Finally, if you want 50mm, but have a consumer-grade camera, you have to get either a G or a third-party lens.

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


<think>

Answer: B: positive