Full frame vs cropped sensor Question: I understand that a lens designed for a full frame camera is used on a cropped sensor camera. You have to apply a multiplier to get tha apparent...

19104 Loc: Philadelphia

I understand that a lens designed for a full frame camera is used on a cropped sensor camera. You have to apply a multiplier to get tha apparent focal length. I.e. on 8x10 film a 300 mm lens is considered a normal lens. And it's considered a short telephoto on 5x7".

Ok So here is question 1 If one uses a lens designed for a cropped sensor camera on a cropped sensor camera. Is the multiplier still used?
and if so why?

And my second question, A 50mm f1.8 dx lens used on dx body is really a75mm f 2.8. Why isn't it marked as such?

I have never owned a cropped sensor digital camera, I have
Used them at work. And never gave it any thought. But now I'm thinking about buying I just can't seem to wrap my mind around this.

LFingar Loc: Claverack, NY

19104 wrote:

I understand that a lens designed for a full frame... (show quote)

That crop sensor ratio (1.6 for Canon, 1.5 for Nikon) has nothing to do with focal length other then as a comparison of the field of view. The focal length of a lens remains unchanged no matter what camera it is on. A 50mm lens on an APS-C Canon will have the same field of view as an 80mm on a full frame. Put that lens on a full frame and it will have the same field of view as any other 50mm on a full frame. Doesn't matter what camera body the lens is designed for. It's all just a comparison of field of view between APS-C and full frame. Other ratios apply for comparison to other size sensors, such as medium format.

imagemeister Loc: mid east Florida

19104 wrote:

I understand that a lens designed for a full frame... (show quote)

First question - YES - the sensor size determines the crop factor not the lens.

Second question - NO - it is NOT really a 75mm and that is why it is not marked as such ! The proper description is : The full frame equivalent field of view on a 1.5X crop factor (size) sensor of a 50mm lens is 75mm.

jethro779 Loc: Tucson, AZ

LFingar wrote:

That crop sensor ratio (1.6 for Canon, 1.5 for Nikon) has nothing to do with focal length other then as a comparison of the field of view. The focal length of a lens remains unchanged no matter what camera it is on. A 50mm lens on an APS-C Canon will have the same field of view as an 80mm on a full frame. Put that lens on a full frame and it will have the same field of view as any other 50mm on a full frame.

This is kind of misleading since the lens in question has to be for a full frame camera. Most crop lenses will vignette on a full frame camera.

LFingar Loc: Claverack, NY

jethro779 wrote:

This is kind of misleading since the lens in question has to be for a full frame camera. Most crop lenses will vignette on a full frame camera.

Well, Canon's crop sensor lenses (EF-S) are not designed to mount on full frame bodies, so that's not a consideration. My understanding of Nikon is that their APS-C lenses can be used on their full frame bodies but that the active size of the sensor is reduced to that of an APS-C, eliminating vignetting. The OP's question wasn't about using APS-C lenses on full frame but about whether or not the ratio applied to APS-C lenses on APS-C bodies. In comparison to full frame, it does. The bottom line is, the ratio is only for comparison purposes. Nothing else. Nothing physical about the lens, or it's designation, changes.

orrie smith Loc: Kansas

19104 wrote:

I understand that a lens designed for a full frame... (show quote)

a cropped sensor lens is less expensive and of lessor quality in my opinion. at to why a cropped sensor (DX) lens is marked a 50mm when it actually has the effect of a 75mm, I do not know, because if you use a DX lens on a FF camera the camera automatically converts to a DX camera and it is still a 75mm lens. Technically it is built to a 50mm spec, but a DX 50mm lens will never, in any situation, be considered a 50mm lens. if you do purchase a DX camera body, please consider only FF lenses and if you ever decide to upgrade to a FF camera, you will not need to reinvest in lenses, and you will save money in the long run.

JohnSwanda Loc: San Francisco

orrie smith wrote:

a cropped sensor lens is less expensive and of les... (show quote)

Lenses are marked with the ACTUAL focal length of the lens. When you put a 50 mm lens on a DX camera, it doesn't turn into a 75mm lens, it just has the field of view of a 75mm lens on a full frame camera.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

19104 wrote:

I understand that a lens designed for a full frame... (show quote)

Question 1 - as Imagemeister notes, focal length remains the same. The multiplier is to give you a sense of the "crop" effect - the narrowing of the field of view.

Question 2. A 50mm lens on a full frame camera is still a 50 mm lens when it is used on a cropped sensor camera, but the field of view on a Nikon for example would be equivalent to the FoV of a 75mm lens on a full frame. The Fstop multiplier applies to the depth of field.

mcveed Loc: Kelowna, British Columbia (between trips)

19104 wrote:

I understand that a lens designed for a full frame... (show quote)

Lenses are marked with their actual focal length, not their apparent focal length. The focal length is determined by the structure of the lens, and it doesn't matter what camera it is mounted on. A 100mm lens will give the appearance of being a 150 meter lens when mounted on a Nikon APS-C camera, a 200 mm lens when mounted on a M4/3 camera, or a 270mm lens on a Nikon 1 camera. It is up to the photographer to figure this out. The lens manufacturer would have a devil of a time trying to engrave all of this on the barrel of the lens.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

19104 wrote:

I understand that a lens designed for a full frame... (show quote)

If you like wide angle work, go to the full sensor. If you like to make humongous enlargements, go with the full sensor. If you like the maximum amount of quality for size of sensor, go with the full sensor. If you want to just take a small part of the frame and make an enlargement, go to full sensor. Otherwise go with cropped. It really is that simple.

NoSocks Loc: quonochontaug, rhode island

JohnSwanda wrote:

Lenses are marked with the ACTUAL focal length of the lens. When you put a 50 mm lens on a DX camera, it doesn't turn into a 75mm lens, it just has the field of view of a 75mm lens on a full frame camera.

Simple, succinct, and accurate response. The OP should thank you.

mwsilvers Loc: Central New Jersey

orrie smith wrote:

a cropped sensor lens is less expensive and of les... (show quote)

Obviously you have not kept up with the latest crop lenses available. The Sigma 18-35mm f/1.8 is a perfect example of a top quality crop lens in both build and optics which is far superior to many lenses that were developed for FF bodies. There are others as well.

orrie smith Loc: Kansas

mwsilvers wrote:

Obviously you have not kept up with the latest lenses available. The Sigma 18-35mm f/1.8 is a perfect example of a top quality crop lens in both build and optics which is far superior to many lens developed for FF bodies. There many are others as well.

Sorry, I did not mean their were no quality lenses built for DX format, there are many.

GoofyNewfie Loc: Kansas City

orrie smith wrote:

... Technically it is built to a 50mm spec, but a DX 50mm lens will never, in any situation, be considered a 50mm lens.

What a crock of merde!

orrie smith Loc: Kansas

GoofyNewfie wrote:

What a crock of merde!

why is it a crock? when will you get a field of view of 50mm with a cropped sensor. and if you put a DX 50mm lens on a full frame camera, the camera automatically reverts to a cropped sensor, so you will not achieve a FOV of 50mm on a full frame camera either.