"Probably the best semi-pro dslr you can buy today"4.5 starson by oscarcolorado
Pros: Incredible level of customization, image quality, low noise at high ISO levels, 51-points auto-focus, built like a tank
Cons: Pricey, 2.5fps if shooting at 14-bit, there may be a learning curve with such an extreme set of features, live-view somewhat difficult to use
Summary: Although I've been a Canon guy for a good time now, I decided to buy the D300: the experience has been amazing. The level of customization is just breathtaking (as well as the 400+ pages manual). Certainly this is not a camera for the newbies. The reward of fully reading the manual and familiarizing with the camera is a big one: total control over the quality of your images.
For a long time I prefered Canon because of a better low-light performance. I've found the Nikon D300's CMOS sensor extremely capable with high detail and well controlled noise levels even at higher ISO levels such as ISO 3200 or even a ISO 6400. Although I won't recommend to use such high sensitivities for every situation, I've found that using ISO800 most of the time is oK and even in many situation the image quality at ISO1600 is way better than what you could get with film.
The camera is built like a tank and the weather seals are great for those taking the camera to dusty or moisty environments.
I've enjoyed specially the 51 points auto focus system. Metering is extremely reliable. The viewfinder is full of valuable information, bright and with a 100% cover zone that delivers no surprises while framing.
Ergonomy is just as good as it gets. The overall feel of the camera is excellent. Although it is somewhat big and on the heavy side, it feels balanced and extremely comfortable. There are a lot of buttons that provide direct access to many features and there is -again- a lot of room for customizing controls.
Regarding image quality and control, the D300 delivers the goods big time. RAW has many flavors (compressed, lossless compressed or without any compression at all) or you may even choose TIFF. The 14-bit provides a wide dynamic range, so you can truly have a really ample space with this extra information to get the exact look you need with the RAW data. I use LightRoom for such matters and the D300 RAW files provide a lot of flexibility. I rarely use JPEGs.
Battery life is very good, even with the 3" LCD monitor. The resolution and brightness of this screen is excellent and the tempered glass is a very nice touch.
Something I don't entirely love of the D300 is the Live-view mode. I really like the live-mode of the Canon 40D and I've found it easier to use tha the D300's. The problem for me is with the auto-focus: sometimes I thought that I took the photograph when I really just performed auto-focus.
This camera is spectacular, yet the price tag is high. Yes, the value is fair, you pay top money for a top camera. A Ferrari may have a fair price for such a superb machine, but if you can't afford a Ferrari you can't afford a Ferarri. With such a price tag some enthusiasts may feel intimidated.
I think that the D300 is a good investment that won't be obsolete soon (not like compact or sub-compact's 6 months lifespan) and the resolution is good enough for big prints or extreme crops. So you can expect to use the D300 for a good time.
There are two good alternatives to the D300: the Sony Alpha 700 and the Canon 40D, but at the end of the day I think that the D300 is very probably the best semi-pro dSLR you can buy today.