Another lie by your camera shop. The Nikon AF-S 50mm F/1.8 G ED lens is a full frame lens (FX) I use it on my D810. And the optics on it are great and it sells for $199. In fact it has better reviews than the F/1.4 G ED lens that sells for $426. I don't know the who the hell that photo shop hires but they should be firing them. No need to buy a $800 lens other than they want to pocket the commission and money they are profiting by. Find a new camera store or order from where I only do: B&H Photo and Camera NY City. Skip the tax and the middle man if you don't live in NY.

That is nonsense. This person does not know Nikon lenses and cameras. The DX lens can be used on a FX camera. The D750, just like my D810 will adjust to the lens in the DX format. You just loose what a full FX lens would give you.

I have done consider research that have resulted the Nikon AF-S 50mm F/1.8 G ED to be the sharpest lens between the AF-S 50mm F/1.4. Unless you need the quarter stop more the 1.8 is the way to go. I use the lens on my D810 and it is outstanding. And how can you beat the price of $200 dollars!

That is simply not true. Talk to any eye doctor and he will tell you some can see up to a 28mm angle of view.

ISO previously ASA 64 is useful for timed photography like one already mentioned. It is also excellent for low noise or grain photos. BUT, that is only if you are really blowing up the print to sizes where noise or grain is going to show up and be unacceptable. Keep in mind that it also includes two other factors. One is your own eyesight and what you are able to notice even blown up and the max MP your camera can handle.

I usually do not post process. What my eyes see thru the camera is what I want to see on print or file. Sometimes post processing changes the photo so much from what you saw because some photographers want their photos to "pop". Sometimes photographers like you and myself want what we take to be just as it was when we viewed it (mind's eye); after all they are memories we store for years to come. Once in a great while i may post process in cases where the camera is not capturing what I am seeing and then and only then I will process a little. I always remind myself that my minds eye view and quality is what I want in the end; after all how do you process your minds eye? How my opinion helps.

Considering you are upgrading from a D300 (DX) you would probably be best served by the next DX camera in the Nikon line the D500 which is the long planned upgrade to the D300 which I also owned for many years. The newer cameras like the D500 would give you low light focus you want, etc. The D500 is good at all of the things you want to do and unless you just want to throw money away it is top notch with little learning curve and you can still use the lenses you presently have. Unless money is no problem (since the D810-good prices now and I own one, or the D850 $3200 without FX lenses) and are at a professional end of photography stick with the D500.

I bought a D810 this year leaving the DX line although many years ago I shot nothing but FX Nikon cameras. The D810 plus quality FX lenses cost me close to 8,000 dollars to replace similar DX lenses. True you can shoot the D810/850 in DX but for what reason. More resolution with FX.

There is no secret to this question. Check your owners manual. It will tell you what memory cards should be used by your camera. It's that simple.

You mention nothing you question regarding the type of camera you use (FX or DX) or how exactly you want to capture pictures (perspective). I am amazed how many people have been focusing on prime lenses of late. Many feel that prime lenses are better than zoom. With engineering accomplishments that have been made with zoom lenses they are, as many reviews have shown, to be equal to prime lenses depending on usage. And then even prime lenses have their shortcomings in IQ. There is no perfect lens after all and I believe (after 40+ years as a photographer) that some are searching for that with primes lenses. Also there is another camp of people that say prime lenses are easier to carry, but when you put 2 or 3 of them together in your bag they will easily equal that zoom that is taking up less space and can cover more instances. The quality zoom could cost you more, but it has far more capabilities to capture more different aspects. Also prime lenses while great if you have the money may have you changing lenses more frequently to get the perspective you want. One should not limit their abilities to capture that perfect shot. My favorite uses for prime lenses are astrophotography (20mm or wider), large aperture lenses for low light, 50mm for boken photography or special purpose lenses like macro. But that does not mean that you can't use a high quality zoom. For instance I own a D810 camera and have owned FX cameras since I started photography and not one of them has a cheap lens. I think the cheapest prime lens is $900. But that being said I have also owned a variety of Canon and Nikon FX camera's (FX and DX) with zoom lenses that do not cost a fortune and by learning about such things as optimal aperture (true on prime lenses too) I can take advantage of the lens sweet spot for outstanding photos.

I did get away from your prime lens question a little but I like to educate photographers. I taught photography in the Army and shot too. Zoom lenses have adaptability, flexibility, and allow you travel light which is a tremendous plus. But again the choice is yours. For me I use two zoom lenses and a Nikon 20mm for astrophotography and whatever, and a 24mm for caves or closed in environments, but I also use zooms.

And for Broken shots they are outstanding!

The reviews on all the fixed focal length lenses by Nikon with the F/1.8 aperture have been excellent. In fact the F/1.8 out performs the F/1.4 in terms of IQ.

I left this out of my answer sort of, there is no difference between the two cameras I own both plus the D810. It's all about the lens.

IQ or image quality comes from the quality of the lens not the camera except in cases of high ISO usage where grain can be quite high depending on how high you set it, but that is it. Buy cheap lenses really hurt image quality. For instance if you own a Nikon D810 why would you buy second rate lenses that do poorly on testing for: distortion, vignetting, resolution, contrast, sharpness abilities (based on aperture), color accuracy, flare, etc. One of the best pieces of advice I can give you that over my 40 years of photography there are things you need to learn regardless of the camera. Camera basics and maybe some advanced things to enable you to get the most out of your equipment. You are always learning. And one more thing always do your research! Research can be through testing sites on the internet, be sure you understand the testing terms or results there goes that learning again. And research from people who have personal experience. One other thing I have done over the years is your can rent a lens and check it out for the day before you make your final decision. Hope this helps.

Talk to any good eye doctor a 35mm DX is not going to give you a normal field of view. Articles on this are greatly misstated. A persons field of view could be as wide as 24mm to 50mm. It is all based on your eyes. The 35mm can offer maybe the most normal perspective for you but that is it. Do not short change yourself. I can usually see as wide as 24-28 in many cases. One good example is in caves. Hope this helps your decision making.

From your message I would assume you are a beginner. So to answer your question IQ or image quality is more than just sharpness, it's also color, contrast, and distortions. And sharpness is not always what a photographer will always need. For instance sometimes you want a slightly off sharp or blurry object to as to the mystique of an image, there's often something called Broken. But the number one thing has to do with the lens and not the camera. You need to read reviews on lenses and talk to friends who are experienced photographers and think it over. Hope this helps.