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Crop Factor with Digital Lenses

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spt_gb said:
Your 200 gives you the Field of View of a 300mm lens on 35mm, but
it may not give you more reach. Reach is a function of pixel
density not crop.
Click to expand...
True, but in practice the FF sensors we've seen have lower pixel densities, which is perhaps good for high ISO performance, but it also means you can't just crop to have the same thing you would have had out of a DX sensor.
spt_gb said:
DOF is a kind of swings and roundabouts thing for landscapes. You
need to stop down more with 35mm to get the same DOF, but then
diffraction effects cut in later so you can stop down more without
losing quality. It's basicaly a tie here.
Click to expand...
Why do diffraction limits cut in later? Is this based on the assumption that FF sensor has lower pixel density? If so, it seems you're contradicting the assumptions of your earlier point about cropping.

In any case, a better example of a situation benefited by DX might be macro photography. With macro photography both the crop factor and increased DOF are typically helping instead of hurting.

Maybe we need stretchy sensors that can be adjusted to different sizes by a dial on the top of the camera. :)
 
Adam Kmiec said:
to have a FF camera offering, but nikon doesn't. it also makes
sense to have a true pro level WA DX lens like a 12-24 F2.8, but we
don't.
Click to expand...
You'd have to have some understanding of how Nikon work (or don't, as the case may be). I'm certainly no expert, but Nikon have always been a little weak on marketing (hence the shock at their 'modern' D80 approach) and production is often a little slow.

Indeed it would make sense to have a FF Nikon, and eventually we will.

It would not make sense for a f2.8 12-24 in my opinion (maybe in Nikon's opinion too).

--
Geoff

WSSA member#68
PBase Supporter

http://www.pbase.com/tuckeruk
 
DonBJr said:
spt_gb wrote:
Click to expand...
...
DonBJr said:
DonBJr said:
DOF is a kind of swings and roundabouts thing for landscapes. You
need to stop down more with 35mm to get the same DOF, but then
diffraction effects cut in later so you can stop down more without
losing quality. It's basicaly a tie here.
Click to expand...
Why do diffraction limits cut in later? Is this based on the
assumption that FF sensor has lower pixel density? If so, it seems
you're contradicting the assumptions of your earlier point about
cropping.
Click to expand...
It's mostly down to the effective amount of enlargement that the image goes through to create a print. A given aperture will create a circle of confusion of the same size for both DX and 35m, but the 35mm needs much less enlargement so the size of the circle in the final print is much smaller.
 
Sometimes we have more pixels than we need, but other times maybe we wish we had more. Certainly when I'm able to frame a picture just how I like it with no post cropping, then 10megapixels seems like plenty for my simple uses.

In terms of DOF... I guess we could simplify the issue and combine it with pixel density. In other words, if a given DOF is sufficient for viewing distance/image size, then what pixel density is required to record that? In other words, if you define an acceptable max size of the 'circle of confusion', then what pixel density is needed to record that? Maybe any additional density beyond that would be wasted except for pixel peeping.

Once you have the standard density, and if you then apply it to sensors of different sizes, then the only way to get more resolution is to have larger sensors. :)

I think I'm understanding better what the previous poster was getting at with DOF. If you've increased the magnification of the subject to cover a larger sensor, then you've lost DOF, but because a smaller sensor needs higher pixel density to make the equivalent image of the larger sensor, you can't get away with as large of a circle of confusion, so maybe it's a wash.

Then again, if that's true, doesn't that also mean that FF doesn't have any advantage for selective focus? Hmm... maybe not because I believe while DOF might be roughly the same, the OOF areas eventually go OOF at a faster rate with longer lenses, and longer lenses are required for an equivalent FOV as the sensor size goes up.

Confusing... heh
 
DonBJr wrote:
...
DonBJr said:
In terms of DOF... I guess we could simplify the issue and combine
it with pixel density. In other words, if a given DOF is sufficient
for viewing distance/image size, then what pixel density is
required to record that? In other words, if you define an
acceptable max size of the 'circle of confusion', then what pixel
density is needed to record that? Maybe any additional density
beyond that would be wasted except for pixel peeping.
Click to expand...
You're confusing two different things. CoC defines how sharp a perfectly focussed image can be. DOF defines how quickly that focus is lost as you move away from the focus point. DOF is not effected by the number and size of pixels. Smaller pixels make the CoC more visible, but only at 100% crop. For a constant print size diffraction effects will look to be constant for a given sensor size. Cropping a smaller area out of the image and printing will however further enlarge the CoC so small pixels do have limits.
DonBJr said:
Once you have the standard density, and if you then apply it to
sensors of different sizes, then the only way to get more
resolution is to have larger sensors. :)
Click to expand...
What you need to do is work out what the CoC is going to look like if you print at a fixed resolution of, say 240 dpi. This will give you the diffraction effect at the largest practical print size for the resolution of the sensor.
 
Adam Kmiec said:
nikon offers a FF DSLR and we as consumers get to choose which one
we want :)
Click to expand...
I'm getting to the point that I hope they never release one and that you all switch to canon. The nonsense of FF fanatics has gone beyond tiresome and would only worsen if they had one to bash us on the head.

--
my gallery of so-so photos
http://www.pbase.com/kerrypierce/root
 
remain a cold cold cold bitter man. what was so fanatical about what I said? did I say FF or die? did I say DX is bad and the devil? no. I said let both exist and the consumers decide what they need and want.

you really need to grow up Kerry.
--

Disagree with me all you like, but remember I have a right to an opinion and a right to state it.
http://www.thekmiecs.com
http://www.adamkmiec.com
 
Adam Kmiec said:
remain a cold cold cold bitter man.
Click to expand...
That's just plain stupidity, Adam. I am not cold or bitter about anything, certainly not FF. I am, however, really extremely tired of you FF fanatics hijacking threads with your whining. Most of the posts in this thread, have nothing to do with the OP's questions.
Adam Kmiec said:
what was so fanatical about
what I said?
Click to expand...
It's always the same old, very tired, song from you and a very few others. That's what is fanatical.
Adam Kmiec said:
you really need to grow up Kerry.
Click to expand...
Coming from you, that's certainly the pot calling the kettle black.......

--
my gallery of so-so photos
http://www.pbase.com/kerrypierce/root
 
That is, if you take a photo with a FF camera through a 300mm lens, and you switch to a DX camera and take a photo with your 200mm lens, and you compare the two images, they will be the same.

The only difference in a DX lens is that the manufacturer can take advantage of the smaller image circle to make a cheaper lens. E.g. aberrations and light falloff which would have been an issue at the edges in an FF lens are not an issue in a DX lens because that part of the image is off the edge of the sensor.
 
with regards to having to switch between a 300 and 200 of course the end result is the same. but you are changing the variables. i'm saying take the same lens on a FF and a DX body; the DX body crops the image leaving you with less of the scene actually captured.

as for light fall off and CA, I suggest you look at the many tests on pbase that show the Canon 5D to have no worse light fall off the the 1D 1.3X based system when using the same lenses.
--

Disagree with me all you like, but remember I have a right to an opinion and a right to state it.
http://www.thekmiecs.com
http://www.adamkmiec.com
 
Adam Kmiec said:
what value did you add to this thread? i and others were having a
great solid conversation until you decided to thread-cr*p. so i'm
just curious, what value did you add?
Click to expand...
Funny that you can post FF propaganda, but others aren't allowed to post their views without it being thread-cr*p. :-)

I added my opinion of a nikon FF and of the hijacking of the thread with your conversation about it. That's certainly just as valuable as your whining about nikon not having FF.

--
my gallery of so-so photos
http://www.pbase.com/kerrypierce/root
 
A 150mm lens is:

A telephoto on a DX camera

A portrait tele on a 6x6 hasselblad

A normal lens on a 4x5 view camera

A wide angle on an 8x10 view camera.

Those of us who have used various film formats realize that argueing about the differece between such a minor change in formats is stupid, or marketing at it's best.

Buy the lenses for the formats that you need and use.

Don't buy a 150mm as a wide angle for a 35mm camera and don't buy a 150mm for a telephoto lens for your 8x10!

If you have used 35mm film cameras in the past and like a 28mm to 80mm zoom, buy a 17-55mm zoom for your DX and be HAPPY!

Nikons big advantage is the use of 1 format for film cameras and (so far) one format for digital cameras. With great interchangability. Some other companies don't even have compatibility between all their CURRENT digital cameras.

--
Edward
http://www.wildlightgallery.net
http://www.pbase.com/qwntm
 
Canon?

I like the idea of all the bodies being DX, and all my old F lenses still working, and having even longer reach than before. I really hope Nikon doesn't make an FF body for the high end, because I don't want to be tempted to want one.
 
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