Crop factor, is it the same as cropping yourself?

[baofeng]

I am a newbie in birding. Initially, I was amazed by the optical zoom camera and camcorder offer. For example, the highest optical zoom for compact camera is 26X and highest optical zoom for camcorder is 70X.

After reading up and understand crop factor, I realized all these are marketing gimmick. For example, the 26X camera and 70X camcorder all have high crop factor, the 70x camcorder having a crop factor of 20X. With the crop factor, I realized it is equivalent to using a (2000mm/20X=100mm lens).

My question is if I use a DSLR camera and a 100mm lens, can I achieve the same picture as the camcorder by cropping it manually in photoshop?

[RJL2005]

I am a newbie in birding. Initially, I was amazed by the optical zoom camera and camcorder offer. For example, the highest optical zoom for compact camera is 26X and highest optical zoom for camcorder is 70X.

After reading up and understand crop factor, I realized all these are marketing gimmick. For example, the 26X camera and 70X camcorder all have high crop factor, the 70x camcorder having a crop factor of 20X. With the crop factor, I realized it is equivalent to using a (2000mm/20X=100mm lens).

My question is if I use a DSLR camera and a 100mm lens, can I achieve the same picture as the camcorder by cropping it manually in photoshop?

A friend of mine constantly boasts that his video digiscoping set-up is equivalent to a 2500+mm lens. His single frame 'grab shots' suggest otherwise....

[Fozzybear]

Not quite sure that's it baofeng - if the lens has 20x optical zoom then it works by physically alters the lens to zoom the image seen by the sensor by 20x. A digital zoom works by leaving the lens as it is and cropping the image recorded by the sensor.

Ignoring lens quality and other factors a system where you record a larger subject image on the sensor will be higher quality than one where you record a small image and crop in, plus with a larger subject it will be easier for AF systems to lock onto the subject and may result in sharper results.

My question is if I use a DSLR camera and a 100mm lens, can I achieve the same picture as the camcorder by cropping it manually in photoshop?

That depends on so many variables it's impossible to say. Cropping right in on a 100mm lens to emulate a, say, 500mm lens is not going to give great results, but compared to a cheap camcorder the quality is likely to be higher if it's a 100mm prime, not a zoom. I've used 300mm lenses and cropped in hard for distant birds and get 'ok' results but there's no way anyone would think it was anything like as good as a native 500mm+ lens.

If you are asking if you need more than a 100mm lens for bird photography then yes, definitely, undoubtedly. The only birds I've been able to photograph with my 90mm lens are the very tame robins in my garden, for most birds a 300mm lens is a bit short... on a full-frame SLR you need 400mm+ really, especially if the birds are distant!

[RAH]

I don't know anything about camcorders, but I do know about crop factor with digital still cameras (DSLRs and point-and-shoots).

Crop factor is best described in how it relates to DSLRs. It refers to the fact that when you put a lens on a non-fullframe DSLR, the effective focal length of the lens is increased. So, for example, if you put a 300mm lens on a DSLR that has a 1.5 crop factor, it behaves like a 450mm lens.

No, this is absolutely NOT like cropping in Photoshop. Say you have a 10MP 1.5 crop-factor camera that delivers images about 3500 x 2400. When you take a picture with a 300mm lens, you get a 3500x2400 image that has its frame filled like you would get using a 450mm lens on a full-frame camera.

If you took the same picture with a full-frame 10MP DSLR with a 300mm lens, you will also get a 3500 x 2400 image, but the subject will fill LESS of the frame than it did on the crop-factor camera (this is what is meant by the crop factor). Sure, you could crop the image down and get a result that fills the frame the same as with the crop-fator camera, but then you WOULDN'T HAVE A 3500x2400 PIXEL image anymore. So, for a crop-factor camera and a full-frame camera that have the same number of MPs, and using the same lens, the crop-factor camera effectively has more reach than the full-frame one.

Purists hate it when people call crop factor magnification, because technically the smaller sensor is causing the image delivered by the lens to the sensor to be cropped, but in practice it operates exactly like magnification. It is absolutely true that a 300mm lens on a 1.5 crop-factor camera operates exactly like a 450mm lens on a full-frame camera.