New blog about Full HD 'digital zoom' on DSLRs using crop - a viable option?

T

thenino

Member
Hey guys,

I just wrote up a new blog post on the theory of a Full HD 'digital zoom' on DSLRs using crop, and I'd like to have a discussion on that topic - is it viable? Is my theory right?

Please check it out here, I also tried to explain how video acquisition with DSLRs works now and how such a crop could work:
http://ninofilm.net/blog/2010/04/26/full_hd_crop_zoom/

Looking forward to your input on that matter!!

Nino
 
I read the blog, and I have one thing to say:
What you REALLY want is just a 1/3 inch 3 CCD camcorder.
Because by getting rid of the line-skipping, you lose every single advantage that your large sensor gives you. You lose the shallow DOF, you lose the sensitivity to light. And you lose the 35mm FOV.
Get a JVC HM-790, and attach 2/3 lenses to it with an adapter. It will give you a nice telephoto crop and you will have no rolling shutter problem.
 
Jesse, thanks for reading.

You might be right with one thing, there might be a little light loss due to the simple fact that no line skipping is employed, but the light sensitivity will still be FAR greater than from any camcorder, especially the tiny 1/3" chips.

But sorry, you are wrong about the depth of field.
The DOF will stay EXACTLY the same. Think about it: The projected image is still the same, therefore the DOF is the same. You only take the middle part of this image and acquire it in 1080p, which results in nothing more than a 3x increase in focal length!

DOF would only be different if you would somehow change the projected image onto a smaller area, but that's not what we do here.

Also, sure you use the 35mm FOV, but that's what you do with any telephoto lens?! No difference whatsoever.
 
Also check out this cinema5D thread, somebody brought up the same thing:
http://www.cinema5d.com/viewtopic.php?f=56&t=3508&st=0&sk=t&sd=a&hilit=good+find+moire

Quote blendin:
"The DOF, yes it is less but, comparing to others film maker it is still better. futher, I read somewhere if you comparing like to like the DOF isnt really change for the crop sensor at all -- we still using the same optical system to get the picture, the only difference is that we now using only the center bit of it, so the DOF is exactly the SAME. the reason that we claim the DOF is less is because you comparing it to a real 600mm lens. But comparing to a 200mm, we get the same DOF if you think it through. By using the crop senor, we only gained the length of the lens not gain in any DOF. But the point is, we arent loss any neither."
 
The DOF does not change on paper but it does in real life !

Your 50 at F2 gives little DOF, but with your crop sensor you are getting a very telephoto field of view

to fit your subject into the frame you must move back or select a wider lens - either action will increase your DOF

-----

Taking the middle is a good idea, partiularly as an option instead of changing to that mode for using telephoto lenses

I have a 400 2.8 it is not that long (say for surfing) on the 5d and also heavy cumbersome and demanding of your tripod

shooting a crop from a 70-200 would be far more practical

S
 
That's exactly what I mean! Only as an additional option of course. I'm talking about the current generation of cameras and what could be possible if somebody comes out with a firmware update. This could NEVER be an alternative to line skipping of course!
 
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