dcampbell52 Loc: Clearwater Fl

:thumbup: :thumbup:
The original question from the op was "Can an FX lens be used on a DX camera?" there was nothing about aperture, noise, or any other qualifying questions within that statement. On Nikon, yes with the only caviat that you mentioned ealier about focus motor. On Canon and other brands, it depends.

Dngallagher Loc: Wilmington De.

the linked video by Tony Northrup was stating that most people forget to multiply the aperture by the crop factor....

BTW - I also use FX lenses on my DX body all the time as well, no complaints, and no special calculations ;)

Screamin Scott Loc: Marshfield Wi, Baltimore Md, now Dallas Ga

Since the OP stated DX & FX, I presume they are shooting Nikon as Canon's designation is EF & EFS. The focus motor is not the only caveat.... The "Entry Level" cameras (D40/x, D60, D3xxx & D5xxx) won't meter with older manual focus lenses (they will, however with older AF lenses), nor will they AF with any lens lacking a built in focus motor.. The "Enthusiast" lineup (D50, D70/s, D80 & D90) will AF with the older AF lenses, but will not meter with any lens not having contacts. The "Prosumer" line (D200/D300/s, D7000 & D7100) will meter with any Nikon MF or AF lens but only AF with AF lenses (of course). In deference to the "Entry Level" Nikon DSLR's, they, along with the Df are the only Nikon DSLR's that won't be damaged by the use of Pre-Ai Nikon lenses.... I started out with the D70s (which I still have) & went to the D300 & currently a D7100... I have an extensive number of older film era lenses & I wanted to be able to utilize them on Nikon's DSLR's, thus I avoided the "Entry Level" bodies...

dcampbell52 Loc: Clearwater Fl

True but as I understood the question, he asked FX on DX and not film on DX so the answer was yes. Nikon is the only manufacturer to maintain compatibility on all of their FX and DX lenses from the first DX camera. Film lenses are hit or miss on complete compatability. Nikon entered the DX market and then later created their first FX camera which had a sensor the "same size" as a 35mm frame of film. Prior to that all of their DSLR cameras were DX beginning in June of 1999. By the way, the D1 was a huge 2.7 megapixel camera that shot 4.5 frames per sec.

http://en.wikipedia.org/wiki/Nikon_D1

jcboy3

It's not a bad idea to use one, just a bad idea to spend a lot of money for FX lens if you only have a DX camera.

The contrary argument is that if you want a fast lens, you are going to have to go FX.

dcampbell52 Loc: Clearwater Fl

Spending lots of money for FX lenses on your DX camera isn't bad if you are assured (like with Nikon) that they will also work on an FX camera. This way you are building your tool chest with lenses that won't be obsolete if you decide to either upgrade to an FX or get an FX and make your DX your second camera. Whith that situation, your lenses are an investment that you can continue to grow into rather than items that you throw away with the DX if you move on.

Dngallagher Loc: Wilmington De.

I believe that the Video used to show why it is a bad idea contained faulty information and should be discounted all together.

IMHO:

Other than the possible loss of some of the auto functionality there is really not a bad reason to use FX on a DX - the sweet spot of the FX lens will be square in the center of the sensor, no vignetting due to crop factor will occur, not like using a DX lens on an FX body. Good deals can be had on FX lenses, perhaps not brand new, but plenty of life left in them for sharp, clear pictures.

jcboy3

And that is the problem with DX; it's treated as a stepping stone to FX, more money, bigger and heavier gear. And why would you throw away a DX camera or lenses?

None of this stuff is an investment; it doesn't grow in value. It's an expense. Spending a lot of money on FX lenses that you might eventually use on an FX camera? That's the issue.

dcampbell52 Loc: Clearwater Fl

It doesn't have to grow in value to be an investment. What it means is that the photographer only has to spend the money on that lens one time. Why would you be stupid enough to buy a 70-300mm DX lens and then 4 years later, dump it and buy a 70-300 FX lens when they will do essentially the same thing and more than likely the FX lens is higher quality and better glass. Now that size was just an example so don't jump on me about 70-300mm fx lenses. The point is that most lenses should last a photographer 8-10 years with decent care.. I have some film lenses that are 20 years old, I do have a couple of DX lenses that are 3 years old and came with a camera.. that are less than good. So, why should I spend $600 to $1000 on a DX lens when I can get the FX lens for a little more and have it longer down the road? That is investing.. it means that you are not spending money twice for the same item... Yes I have both DX and FX bodies now and ALL of my lenses, both DX and FX will work on my cameras.. but, I tend to gravitate to the FX lenses on all of my cameras. I guess I was stupid when I started buying FX lenses for my DX cameras.. I should have bought DX so that I could replace them then I got FX bodies..To me, that seems like the way the US Government buys things... Not me. And I don't throw away a DX camera.. I use them.. I am the one on here that keeps telling people that DX cameras have a use by professional photographers... I use a DX instead of a teleconverter.. I can put a 300mm FX lens on my DX camera and change the crop on the DX to 1.3x which is in effect acting as a 2x converter but I don't lose the aperture.. Best I can do on an FX camera is change it to DX mode or 1.5.

jerryc41 Loc: Catskill Mts of NY

Having a good selection of FX lenses will make justifying the purchase of an FX body much easier.

dcampbell52 Loc: Clearwater Fl

Very true Jerry.. Plus, keeping the DX body gives me the extra reach without a teleconverter and the loss of f/stops that a TC creates. My DX body will go 1.5 natively and I can go to 1.3x mode and it crops as a 2x. Thats nice making a 300mm lens act like a 600 with no loss of aperture. and my DX is a 24mp camera so I have room for the crop.. could I do it in Lightroom? sure, but I would ratther get the original image close and then play.

jcboy3

You really shouldn't use the word stupid unless you are describing yourself.

I wonder why you are hanging on to "less than good" DX lenses? If you can't sell something when you buy a better quality replacement, then I can see why you wouldn't want to buy a DX lens if you might get a comparable FX lens in the future.

Just keeping to your example, the 70-300mm FX lens is comparable to the 55-200mm DX lens, but costs twice as much. Which is the primary reason for buying a DX lens for a DX camera.

This whole "down the road" thing presumes that everyone should aspire to owning an FX camera. Which Nikon and Canon and every other DSLR manufacturer desires. But doesn't make sense for most people.

I have FX and DX cameras, mostly FX lenses but a couple of DX lenses that are comparable, and can be used for backup on the DX camera. If I need to bring backup, the DX camera/lens combination is definitely smaller and lighter.

JimH123 Loc: Morgan Hill, CA

I use FX type lenses on a DX type body all the time and I see no downside.

I suspect what Tony Northrup is alluding to is the thinking that the DX type camera is only using light from the center of the objective lens since the light cone falling on the objective is broader than the sensor and making it appear as if the objective is smaller.

I'm not sure this adds up.

One test to do would be to take a FX lens on a FX body and spot meter on a subject and make note of the settings. Preferably do this without using auto ISO, WB, etc and use Aperture or Shutter Priority mode so only one variable can change.

And then repeat the same experiment with the same lens and the DX body and see if the camera is seeing the lighting conditions the same. Having not taken the time to try this, I suspect the two camera will both record the same settings.

oldtigger Loc: Roanoke Virginia-USA

His commentary has nothing to do with light gathering or exposure.
He is referring to the diffraction limiting of the camera/lens system.
He is not saying you can close down and get the same exposure, he is saying you can close down without destroying your IQ.
Different animals, totally different subjects.

Searcher Loc: Kent, England

If you watch the video, at about the 2 mins mark, Mr Northrup converts the focal length x multiplying by the crop factor. He also mentions that the lens behaves as if it had a different aperture because the depth of field is changed.

He is saying (badly) that a FX lens 24-70mm f/2.8 lens when fitted to a Nikon with a crop factor of 1.5 (DX) will have an apparent or comparative focal length of 36-105mm and a depth of field equivalent to that of using an aperture of f/4.2 on a FX body.

He is describing the depth of field.