Help on future purchase

Devinhullphoto · May 30, 2013

I currently own a D5100 and while its a great camera, I really wanna upgrade to the D7100 (or newer model if one replaces it by next fall). Right now I have the standard 18-55mm, 55-200mm, 50mm 1.8G, and a random 135mm 2.8.

I would love to get the 70-200 F4 to replace my 55-200, and here is my dilemma. I don't think I will be making the jump to FX anytime soon or maybe never since this isn't my profession and I know that the 70-200 F4 is designed for FX camera and I won't be able to use it to the fullest on a DX. I wanna know if I should get a different zoom or get the 70-200 F4 just in case I make the leap.

I'm also curious if I should upgrade my 18-55 before getting the D7100 or does it perform well with a D7100?

Any help or advice on lenses I should consider would be very appreciated.

Gary_A · May 30, 2013

The D7100 just came out, so I doubt it will be replaced by the fall. There is no problem using an FX lens on a DX body, the restriction is using a DX lens on an FX body.

gardy · May 30, 2013

What's your price range for lenses after upgrading bodies?

Devinhullphoto · May 30, 2013

gardy said:
What's your price range for lenses after upgrading bodies?

Pretty much anything. I don't have the cash to just throw down, but I can save money pretty fast.

Overread · May 30, 2013

Devinhullphoto said:
I would love to get the 70-200 F4 to replace my 55-200, and here is my dilemma. I don't think I will be making the jump to FX anytime soon or maybe never since this isn't my profession and I know that the 70-200 F4 is designed for FX camera and I won't be able to use it to the fullest on a DX.

The FX lenses might be made for FX format, but that doesn't mean that they perform poorly on the DX format. Heck because you're seeing the middle of the frame and cutting the corners lenses on DX can often perform superiorly over their performance on FX if you compare the edge sharpness and quality aspects.

In the end the format doesn't matter so much as the quality of the glass - if you want the quality glass; if you can afford it; if paying for it won't leave dependants upon your income without - then by heck do it. Doesn't matter if you earn off the gear, if you can justify and afford it with your income and you enjoy photography then do it

TCampbell · May 30, 2013

Just to be clear, you're not losing anything when you use an FX lens on a DX body.

In days of 35mm SLR cameras, the "image circle" projected by the lens into the sensor body had to be large enough to cover the size of the 35mm negative frame with adequate optical quality (the image is usually a bit larger but quickly degrades at the edges.)

When digital came along, the most expensive component in the camera was that digital sensor. It was VERY expensive. Camera makers hit upon the idea that they could substantially lower the cost by producing a camera body that used a sensor with a reduced physical size, but placed inside a body that could still use all the 35mm lenses. Basically that means the sensor is only capturing the part of the image near the center of the lens' "image circle" -- it's as if you took a full 35mm frame but then cropped away the outer edges of the image, then enlarged the image to print the same size. Hence the name "crop frame" sensor. The size they chose happened to be nearly the same size as the Advanced Photo System "Classic" film negative size (that's where the acronym "APS-C" comes from.) This massively reduced the expense of the camera and allowed for compatibility with regular lenses.

DSLRs were also eventually produced with sensors which were the same size 35mm film camera negatives, but these were extremely expensive (they still are quite a bit more expensive... an "entry" level full-frame body is just slightly less than $2000 for the body-only).

So where do DX lenses (on Canon they're called EF-S) fit into the story?

It was realized that since the APS-C size DSLRs aren't capturing the full size image, that you could save a lot of money by building lenses that didn't project a large image circle. Also, the optics only need to be good enough to hold image quality out to the corners of a much smaller sensor size. This means the elements can be smaller, they're easier to grind to precision, the lens can be more compact and it will weight less. And (this is the best part) there's absolutely NO loss of image quality. The image quality is every bit as good. The only difference is that the lens doesn't project an "image circle" into the sensor body large enough to reach the corners of a full-frame sensor (that is, a sensor which is as large as a 35mm film negative.)

If you buy an FX lens, you may use it on EITHER a DX or FX body. If you buy a DX lens, it will really only be suitable on a DX body... only because it cannot fill the frame of an FX body.

If you want to own a 70-200mm lens, do not let the fact that you have a DX body stop you. The lens will work flawlessly on your camera.

Also.. there is no difference in focal length between FX and DX. The focal lengths of the lenses are always stated as "true" focal lengths -- not "effective" focal lengths (as are often stated on point & shoot cameras). A 100mm focal length on a DX body and a 100mm focal length on an FX body are the same... the difference is only that in a DX lens, the image spills off the sensor and only the middle of the image is captured. This creates the illusion that you've "zoomed in" an extra 50% (that's the Nikon crop-factor for APS-C) on a DX body (so it "seems" like you're using a 150mm focal length -- but of course if you took an FX image and cropped in a tighter you'd get EXACTLY the same effect.)

Devinhullphoto · May 30, 2013

TCampbell said:
Just to be clear, you're not losing anything when you use an FX lens on a DX body.

In days of 35mm SLR cameras, the "image circle" projected by the lens into the sensor body had to be large enough to cover the size of the 35mm negative frame with adequate optical quality (the image is usually a bit larger but quickly degrades at the edges.)

When digital came along, the most expensive component in the camera was that digital sensor. It was VERY expensive. Camera makers hit upon the idea that they could substantially lower the cost by producing a camera body that used a sensor with a reduced physical size, but placed inside a body that could still use all the 35mm lenses. Basically that means the sensor is only capturing the part of the image near the center of the lens' "image circle" -- it's as if you took a full 35mm frame but then cropped away the outer edges of the image, then enlarged the image to print the same size. Hence the name "crop frame" sensor. The size they chose happened to be nearly the same size as the Advanced Photo System "Classic" film negative size (that's where the acronym "APS-C" comes from.) This massively reduced the expense of the camera and allowed for compatibility with regular lenses.

DSLRs were also eventually produced with sensors which were the same size 35mm film camera negatives, but these were extremely expensive (they still are quite a bit more expensive... an "entry" level full-frame body is just slightly less than $2000 for the body-only).

So where do DX lenses (on Canon they're called EF-S) fit into the story?

It was realized that since the APS-C size DSLRs aren't capturing the full size image, that you could save a lot of money by building lenses that didn't project a large image circle. Also, the optics only need to be good enough to hold image quality out to the corners of a much smaller sensor size. This means the elements can be smaller, they're easier to grind to precision, the lens can be more compact and it will weight less. And (this is the best part) there's absolutely NO loss of image quality. The image quality is every bit as good. The only difference is that the lens doesn't project an "image circle" into the sensor body large enough to reach the corners of a full-frame sensor (that is, a sensor which is as large as a 35mm film negative.)

If you buy an FX lens, you may use it on EITHER a DX or FX body. If you buy a DX lens, it will really only be suitable on a DX body... only because it cannot fill the frame of an FX body.

If you want to own a 70-200mm lens, do not let the fact that you have a DX body stop you. The lens will work flawlessly on your camera.

Also.. there is no difference in focal length between FX and DX. The focal lengths of the lenses are always stated as "true" focal lengths -- not "effective" focal lengths (as are often stated on point & shoot cameras). A 100mm focal length on a DX body and a 100mm focal length on an FX body are the same... the difference is only that in a DX lens, the image spills off the sensor and only the middle of the image is captured. This creates the illusion that you've "zoomed in" an extra 50% (that's the Nikon crop-factor for APS-C) on a DX body (so it "seems" like you're using a 150mm focal length -- but of course if you took an FX image and cropped in a tighter you'd get EXACTLY the same effect.)

Thanks for the info! That cleared up a lot. The part I was worried about was the focal length. Even if I never upgrade to FX I will still have great glass which is the most important part of the camera. If I ever decide to jump to FX, at least I will have a head start on a good lens.

Thanks for all the input, I had a lot of misconceptions about it and now it's all pretty clear.