AKA…the DX Crop FactorDx vs. Fxin terms of 35mm filmDSLR Chip Size
Copyright Notice• Attribution-NonCommercial-ShareAlike CC BY-NC-SA• This presentation is for educational purposes only. No money is being madeand is provided with similar allowances for other educatorsto use for non-profit, educational purposes.• Images are from various sources, including many of my own.If you would like to high res images I have shot, please visitwww.DrewLoker.com for various work online.• If you are the original author of any of the samples, pictures, text, etc.please let me know if you object to the usage and I willremove your material promptly.Photo by Drew Loker
35mm Film sets the standard• 35mm film measure 35mm x24mm• When the first Digital SLRs cameout, they had the form factor ofthe film cameras, but the sensorsize was half the size of a filmnegative…resulting in a change inthe field of view.
35mm was NOT perfect• 35mm film measure 35mm x24mm which is approximately a2:3 aspect ratio• This mean that what you see isNOT what you will get EXCEPTfor 4x6s.– 2:3 = 4x6 20x30 (or .66 factor)– 2.5:3.5 5x7 = (.71 factor)– 3:4 = 6x8 (or .75 factor)– 4:5 = 8x10, 16x20 (.8 factor)
Lens Focal Lengths• A stated lens focal length wasbased on the size of the imagearea.• So, a 50mm lens (the yellowcircle) on a 35mm negative(blue box) was designed tocover the entire negative.
Lens Focal Lengths, cont.• But the same 50mm lens wasMUCH larger than the DXsized sensors. So, what theuser saw (I.e. field of view)was similar to that of a longerlens, specifically, a 75mmlens.
Lens Focal Lengths, cont.• Then lens manufactures “gotsmart” and designed a lenswith an opening just bigenough to cover the size ofthe sensor…thus the DX lenswas born.
Lens Focal Lengths, cont.• The only problem is if you tryto use a DX lens on a fullsized sensor.• You literally get a circle fromthe heavy vignetting of thelens on to your image.
FOV Crop – A benefit?• This resulting 1.5x crop factor isperceived by most as a benefit…ifyou are wanting to shoot LONG…and a disadvantage if you arewanting to shoot wide.• 70-200mm lens has an effectiveFOV as a 105-300mm. 300mm isgood for sports and wildlife.• 18-55mm is actually a 27mm-82mm…so not really a wide anglelens.• 10-20mm lens is actually a 15-30.
Camera Companies Release FX• In the last couple of years, both Nikon and Canonhave released professional level full sized sensors.(ok…Canon was first). But the consumer camerashave YET to see a full size camera resulting ineven more confusion to the focal length Field ofFiew Crop.• Some lens are designed only for DX sizedsensors…other lenses will work on both.• The smaller sized lens is good for portability…butbad if you ever upgrade to a different camera.
Not all cameras have the sameFOV Crop Factor• Crop factor simply means you take thestated focal length and multiply it times thefactor number. I.e. FL x 1.5 = effectiveFOV.• Nikon has been consistent with all of it’sAPC sized bodies with a crop factor of 1.5• Other camera manufactures have produced:1.7, 1.6, 1.3, etc.
Popular NikonDX lenses vs. FX lenses• 18-200 = 27-300• 18-55 = 27-82• 12-24 = 18-36• 28-105• 24-120• 24-70• 14-24• 300• The above lenses will not workon a FX body.• If the above lenses are used ona DX body, then the FL has tobe multiplied by 1.5* Note: There are other lens manufactures with even more focal length…and some of those are designedto work with both FX and DX…or just DX. Generally, DX lenses are smaller and less expensive.
Comparison of CamerasFX = Full Frame35mm Equivalent DX = APSNikon D40Pentax istCanon Rebel xtiNikon D3Canon Mark Id3P&S = APCCanon A85Canon 570NikonCoolpixJust aboutall pocketP&ScamerasCell Phone