FX vs DX format

[donpet]

How do they arrive at a 1.6 lens factor?
Which lens has the greatest magnification between a 400 mm on a dx camera or a 300 mm lens on a fx lens. Assuming if you blow up the fx image X2. Ill be shooting animals in africa and want to get the largest prints. Using a long lens with a tripod is not possible !

[groovyone]

Nikon has a 1.5x factor. It has to do with the area of the sensors. The smaller APS-C only uses a section of the image that the lens projects onto an FX sensor, and the math works out to be the 1.5x lens factor.

FX is full frame, so there is no lens factor. A 300mm looks like a 300mm and a 400 like a 400.

Dx is the crop sensor so a 300mm will look like a 450mm on a Fx camera, and the 400mm with give an image like a 600mm on the full frame.

Make sense?

[ggeen]

Keith did a really good job explaining it here. To look at it from a more technical standpoint, here is a link from NikonUSA.com
Camera Lens Explained | DX & FX Format Lenses from Nikon

Also, this topic is well discussed here in the forum.

[Abel]

Our Pixtus Photography Cheat sheet will also teach you how to calculate that... See the portion thats titled FIELD OF VIEW

Pixtus Photography Cheat Sheet

[PhotoByLeal]

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[Jaymoney$]

Originally Posted by PhotoByLeal

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FREE Pixtus Photography Cheat Sheet

[donpet]

According to the NIKON info if i shoot the DX 400 lens at 600mm,i will get more magnification with it than the FX lens at 300mm. I calculated the ratio of the FX area to the DX is 2.25 not 1.5 so i still dont understand that !

36x24 / 24x16 =2.25

[Abel]

It's not 2.25x. The FX sensor is 1.5 times larger than the DX sensor. So...

400mm x 1.5 DX Body = 600mm
400mm x 1.0 FX Body = 400mm

300mm x 1.5 DX Body = 450mm
300mm x 1.0 FX Body = 300mm


See the attached image I just made to see how they get the 1.5 factor... I rounded off the DX sensor size...

[Photogdude]

Originally Posted by donpet

According to the NIKON info if i shoot the DX 400 lens at 600mm,i will get more magnification with it than the FX lens at 300mm. I calculated the ratio of the FX area to the DX is 2.25 not 1.5 so i still dont understand that !

36x24 / 24x16 =2.25

the size of the sensor (FXvDX) is irrelevant to magnification(for your org question) A 300m lens is gong to project the same size image, whether its on a fx or dx. It's just the dx is physically smaller so it just crops the image as compared to the fx.

Back to your org question, it's kinda hard to answer, but in a nutshell, if you want to make larger prints go for the sensor with most megapixles (this doesn't imply best quality, cause there are many other factors, including pixel size, noise, dynamic rage, but math dictates that the more megapixels the less you will have to upres the file for a larger print), but if you want to get closer to the animals go for the longer lens.

just remember more mega pixels doesn't always equal better image quality. if it were me i would get a 400mm on a full frame, rather then a 300 on a dx.

[kenw]

and here's another way to look at it that talks to why a 4x6 print from a crop looks "more zoomed" than the same on a full frame.