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02/07/2006 03:39:06 PM · #1 |
| what advantage/disadvantage does a cropped sensor has ? other than magnifying the focal length... |
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02/07/2006 03:46:19 PM · #2 |
They cost less to make. You can fit more of them on a single sheet of material in the manufacturing process. If there's a flaw int he process, it affects fewer chips; if you have 32 chips on a single raw sheet, and one corner screws up, you lose 4 chips, or 1/8 of the ouput. If there were only 4 chips on the same raw sheet, you'd lose a quarter of the output. This is the main reason why larger sensors are MUCH more expensive; it's a quality control issue.
Robt.
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02/07/2006 03:47:25 PM · #3 |
Originally posted by Bear_Music:
They cost less to make. You can fit more of them on a single sheet of material in the manufacturing process. If there's a flaw int he process, it affects fewer chips; if you have 32 chips on a single raw sheet, and one corner screws up, you lose 4 chips, or 1/8 of the ouput. If there were only 4 chips on the same raw sheet, you'd lose a quarter of the output. This is the main reason why larger sensors are MUCH more expensive; it's a quality control issue.
Robt. |
and there is _always_ flaws in the process... Also, there is nothing to actually say that 35mm is a good size, other than history.
Message edited by author 2006-02-07 15:48:15. |
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02/07/2006 03:52:07 PM · #4 |
Originally posted by rami:
what advantage/disadvantage does a cropped sensor has ? other than magnifying the focal length... |
Not sure what you mean. Are you talking about the crop factor? Your camera (the 350D) uses lenses made for 35mm film (or sensor known as a full frame sensor). Since your sensor is smaller then the image circle of the lens the sensor only picks up part of the total light (or image) entering the camera. This is known as a crop factor. In your case I think it is 1.6 so, if you have a 200mm lens it is the same as 320mm lens on a 35mm camera.
Hope this helps. |
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02/07/2006 03:53:26 PM · #5 |
Originally posted by Gordon:
and there is _always_ flaws in the process... Also, there is nothing to actually say that 35mm is a good size, other than history. |
Right; should have said "when", not "if".
The 35mm "standard size" has an interesting history; the original continuous films were developed for the motion picture industry and they ran through the camera vertically; when folks started developing 35mm still cameras, they ran the film horizontally, and so the "standard" 35mm film image was actually LARGER than the motion picture standard. It's just an accident of development, basically.
Robt.
Message edited by author 2006-02-07 15:54:21.
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02/07/2006 03:57:43 PM · #6 |
Another "advantage" is that a cropped sensor uses the "sweet spot" of a pre-existing, non-digitally-developed lens. Digital sensors have a more difficult time than film does reading light coming in at an oblique angle, so film-adequate performance int he corners can appear very soft in the digital world. Lenses developed specifically coe APS-C sensors like Canon's are designed to minimize this problem, so the 10-22mm Canon EFS lens has better corner performance on the cropped sensor than the equivalent, pre-dogotal 16mm lens has in the corners of a full-frame sensor.
R.
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02/07/2006 04:01:47 PM · #7 |
I agree with both responses so far... semiconductor defects are pretty constant on a defects per area basis, so if you more than double the area of the sensor, expect more than double the fallout. Actually, if you do the statistics, it's much worse than this. Yield falls much faster than you'd expect.
There really is no reason that 35mm-sized sensors should be "the norm" rather than APS-C sized ones, or something else entirely. But (you knew there was a but) as Gordon stated, "except history," and history is a strong force. The basic format of the 35mm SLR is so usable, the amount of hardware (e.g. lenses)available so great, and the general photography knowledge base so "35mm-centric" that it makes 35mm a big attraction.
The very fact that the 36x24mm sensor size nearly maximizes the use of the image circle thrown by all lenses designed for this film format, and the fact that this is about the biggest sensor you could reasonably put in a package the size of a 35mm SLR, which is arguably among the most ergonomic of all camera formats, means that "Full Frame" 35mm is here to stay. So, IMO is APS-C, and the lenses available for it will continue to increase.
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02/07/2006 04:04:07 PM · #8 |
A lot people are still mixing up crop factor and magnification factor and to be honest, I can't seem to be able to get a straight answer for anyone.
Here is my interpretation. Please tell me if I'm wrong.
If you're camera has a 1.6x factor, it doesn't mean that your lenses are 1.6x stronger (magnification), it means that for a given lens length (e.g. 50 mm), you will actually be shooting a field of view that is 0.625 the size of a field of view if you'd be shooting film on a 35mm camera (e.g. 50 mm on a 1.6x crop DSLR is as wide as a 80mm lens on a 35mm film SLR). This doesn't mean that you are actually shooting at 80mm, only that your field of view (angle) is like shooting with an 80mm lens.
Does this make sense? Ouch! I think I just hurt my brain.
Message edited by author 2006-02-07 16:04:47. |
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02/07/2006 04:07:42 PM · #9 |
Take a dinner plate.
Put it on a sheet of paper. Draw a circle around it.
This is the area that a 35mm lens focuses tne image upon.(not to scale)
Now draw the biggest rectangle you can fit in to that circle. Make it longer than it is wide at about 3:2 ratio)
That's a 35mm full frame sensor.
Now draw a rectangle with about the same ratio, but 1.6x smaller, within that
That's what most digital sensors actually capture out of that initial big circle.
You crop a bit out of the middle of the image.
If you captured it on a 35mm or full frame format, you'd have more image, so it would look relatively wider angle.
With the 1.6x crop, you pull a bit out of the middle of that image, making it look like more of a telephoto shot, or zoomed in/ higher magnification.
So it is in reality a crop, but is an effective magnification.
Make sense ? Just get the dinner plates out.
The reason it isn't an actual longer focal length, is that effects like compression are the same as for the original 35mm focal length lens.
Message edited by author 2006-02-07 16:08:40. |
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02/07/2006 04:10:07 PM · #10 |
Originally posted by Beagleboy:
A lot people are still mixing up crop factor and magnification factor and to be honest, I can't seem to be able to get a straight answer for anyone.
Here is my interpretation. Please tell me if I'm wrong.
If you're camera has a 1.6x factor, it doesn't mean that your lenses are 1.6x stronger (magnification), it means that for a given lens length (e.g. 50 mm), you will actually be shooting a field of view that is 0.625 the size of a field of view if you'd be shooting film on a 35mm camera (e.g. 50 mm on a 1.6x crop DSLR is as wide as a 80mm lens on a 35mm film SLR). This doesn't mean that you are actually shooting at 80mm, only that your field of view (angle) is like shooting with an 80mm lens.
Does this make sense? Ouch! I think I just hurt my brain. |
There isn't any difference. Set up a tripod and shoot a picture with a full-frame camera and a 160mm lens, then shoot the same shot with an APS-C camera and a 100mm lens; the results will be identical. Put the 160mm lens on the APS-C camera and shoot the same shot. Crop the full-frame shot to show the same area as the APS-C version, and they will be identical, excluding any differences in grain or noise that might creep in.
R.
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02/07/2006 04:10:29 PM · #11 |
Originally posted by Gordon:
...Make sense ? Just get the dinner plates out. |
mmmmm, dinner... drool
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02/07/2006 04:39:53 PM · #12 |
| Cool. Thanks. Time to go put psghetti on my dinner plate. Yummmm! |
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02/07/2006 05:08:51 PM · #13 |
Originally posted by Bear_Music:
Originally posted by Beagleboy:
A lot people are still mixing up crop factor and magnification factor and to be honest, I can't seem to be able to get a straight answer for anyone.
Here is my interpretation. Please tell me if I'm wrong.
If you're camera has a 1.6x factor, it doesn't mean that your lenses are 1.6x stronger (magnification), it means that for a given lens length (e.g. 50 mm), you will actually be shooting a field of view that is 0.625 the size of a field of view if you'd be shooting film on a 35mm camera (e.g. 50 mm on a 1.6x crop DSLR is as wide as a 80mm lens on a 35mm film SLR). This doesn't mean that you are actually shooting at 80mm, only that your field of view (angle) is like shooting with an 80mm lens.
Does this make sense? Ouch! I think I just hurt my brain. |
There isn't any difference. Set up a tripod and shoot a picture with a full-frame camera and a 160mm lens, then shoot the same shot with an APS-C camera and a 100mm lens; the results will be identical. Put the 160mm lens on the APS-C camera and shoot the same shot. Crop the full-frame shot to show the same area as the APS-C version, and they will be identical, excluding any differences in grain or noise that might creep in.
R. |
Well no not quite the same, the dof will be different (more DOF for the 1.6x crop).
That is
if you shoot with the same settings and distance with a 100 on 1.6x vs a 160 on FF.
Message edited by author 2006-02-07 17:11:01. |
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02/07/2006 05:34:25 PM · #14 |
Originally posted by Bear_Music:
Originally posted by Beagleboy:
A lot people are still mixing up crop factor and magnification factor and to be honest, I can't seem to be able to get a straight answer for anyone.
Here is my interpretation. Please tell me if I'm wrong.
If you're camera has a 1.6x factor, it doesn't mean that your lenses are 1.6x stronger (magnification), it means that for a given lens length (e.g. 50 mm), you will actually be shooting a field of view that is 0.625 the size of a field of view if you'd be shooting film on a 35mm camera (e.g. 50 mm on a 1.6x crop DSLR is as wide as a 80mm lens on a 35mm film SLR). This doesn't mean that you are actually shooting at 80mm, only that your field of view (angle) is like shooting with an 80mm lens.
Does this make sense? Ouch! I think I just hurt my brain. |
There isn't any difference. Set up a tripod and shoot a picture with a full-frame camera and a 160mm lens, then shoot the same shot with an APS-C camera and a 100mm lens; the results will be identical. Put the 160mm lens on the APS-C camera and shoot the same shot. Crop the full-frame shot to show the same area as the APS-C version, and they will be identical, excluding any differences in grain or noise that might creep in.
R. |
Aside from the DOF being greater with the shorter lens. |
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02/07/2006 05:45:19 PM · #15 |
Originally posted by kirbic:
....The very fact that the 36x24mm sensor size nearly maximizes the use of the image circle thrown by all lenses designed for this film format, and the fact that this is about the biggest sensor you could reasonably put in a package the size of a 35mm SLR, which is arguably among the most ergonomic of all camera formats, means that "Full Frame" 35mm is here to stay... |
I often scratch my head about the 2:3 ratio thing in digital because I assume a square sensor would be better at maximising the image thrown by the lens (like the oldie cameras). I guess that's why there was some push for the 4:3 ratio on the smaller cameras (and some dSLR's) but why not square again?
On the crop vs. magnification thing; well to a point everything is really just a crop right? :-) A 1200mm lens is just cropping out a small portion of a 15mm fiel of view (ok, I know there are physical limits and distortion issues). The len has a focal length of whatever it says it is on a 1.6 or FF 35mm; just you get a smaller portion in the middle of that lens on a 1.6 sensor.
I think what confuses everyone (all the change in dof e.t.c.) is just a function of having to stand further back to get the same stuff in the image. |
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02/07/2006 05:50:09 PM · #16 |
i think the 1.6 crop factor magnification will be the equivillant of a digital magnification and not actual focal length ... only difference is that its a clean magnification with no pixalization .. you lose no data you only cram more pixels into smaller areas ...
anyway its quite interresting hearing all your opinions...
so bottom line ? .. a cropped sensor is no worse or better in quality than a normal one ? |
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02/07/2006 05:53:31 PM · #17 |
robs : not just cropping .. if you crop the same image at the same Mega pixels of a frame shot with a normal 35 mm frame size.. and then crop it to the size of that same picture taken with a camera with a cropped sensor, the equivillant will be two identical picture ( same DOF ) but different resolution.. the way i see it is... its good to focus on the good center spot of a lense while not losing resolution ...
i don think its correct to convert a 300 mm lense to its 480 equivillant.. its technically wrong |
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02/07/2006 05:55:05 PM · #18 |
This is probably the most confusing item in digital photography - all told!
From an engineering point of view (no pun), that a given lens for a particular camera, say a 35mm/Canon lens for a Canon 35mm camera, has a precise focal plane otherwise known as the film plane. Though there are many other factors, as most film photographers know, if the film is ever for any reason held off plane its not focused realtive to the rest of the image.
If you look at any bellows focused lens, you notice that for any given lens, dist to subject you have a precise focus point, the same thing holds true in the digital world. Its physics, not magic.
IE: The main difference from a Canon 20D to say a 1Ds-II is literally the size of the sensor (physical only dim in W x L). The planar position of that sensor is precisely in each - otherwise the same lens would not focus on both cameras.
So then the difference comes down to two things: 1) the dot/pixel pitch (their size and moreover how far apart they are if they have spaces), and 2) the W x L or field of view.
The next major contributor is that despite of popular understanding, the fact is that all digial images are considered at 72dpi in the actual image file world - I will explain later.
Now then, if you you took a Canon 20D with a 50mm lens for that camera and only imaged the center 5/8 of the field of view, and, then crammed the sensor with 1.6x the pixels of the 1Ds-II - the net image file at the standard of 72dpi would be identical. However for a moment, the pixel pitch is exactly where the money is!
So in the end, if you in your "view finder" and measure a particular subject items' W x L at the film plane (as you could on a ground glass large format), its the same size in both camera's. so did it magnify, no, its appearant.
If the reasoning were true that it actuall magnify's, that would only be due to the film plane being farther from the lens - if you remember all the way back to the basics of optics even your eye as example. The eye is, in all pratically thoughts, nothing more than a bellows focus camera. The image on the film plane - your retina, is upside-down and backward's, totally reversed as the light rays in refraction (a lens) are bent, crossed as an "X" at the aperature and then the distance too the film plane yields a mag factor - again the glass of lens not changing in shape. The reason some people need glasses and others dont is the shape of the lens mainly. Once that's corrected (which is how lasix works) the focus mechanics is the same.
In al the terms used by others so far - the crop to full is the clincher. Thats right to my point that in the image file world its all relative to 72dpi... remember screens is not finite across the board so not all things are equal in one screen resolution to another. However, PRINT each at 72DPI and see what happens - but you have to remain on the same platform, IE a 1Ds file with the same lens too a 20D say. the minute you go from one camera too another, the dot pitch thing takes over.
I hope that I have not offended anyone here in a long winded lecture, but this my personal peeve!
jf |
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02/07/2006 06:02:07 PM · #19 |
Originally posted by Beagleboy:
A lot people are still mixing up crop factor and magnification factor and to be honest, I can't seem to be able to get a straight answer for anyone. |
A lens projects the image onto a focal plane at the back of your camera to record the image. The sensor of most digital cameras is considerably smaller than 35mm film, so the image is cropped. If you print a frame of 35mm film and an image captured from a Digital Rebel to standard 4x6" size, the smaller image from the Rebel must be magnified 1.6X to get the same print size. Thus, the image is both cropped AND magnified, which has the same apparent effect as a 1.6x longer zoom, except for the depth of field... whatever background details were fuzzy will be just as fuzzy whether the image is cropped or not. |
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02/07/2006 06:16:20 PM · #20 |
Originally posted by kyebosh:
Well no not quite the same, the dof will be different (more DOF for the 1.6x crop).
That is
if you shoot with the same settings and distance with a 100 on 1.6x vs a 160 on FF. |
This is not true. For the same reproduction ratio, at a given physical aperture, DOF is identical regardless of the focal length of the lens. At a 1:1 reproduction ratio, my 60mm macro has exactly the same DOF as a 105mm macro lens. I used to believe what you are saying here (essentially, that a 60mm macro lens would have more DOF than a 105mm macro lens), but it turns out not to be true.
R.
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02/07/2006 06:21:25 PM · #21 |
Originally posted by jefalk:
the minute you go from one camera too another, the dot pitch thing takes over.
I hope that I have not offended anyone here in a long winded lecture, but this my personal peeve!
jf |
though the pixel pitch of a 1DII sensor and a 20D sensor are different, which mixes things up again and makes it more fun... |
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02/07/2006 06:29:12 PM · #22 |
Originally posted by Bear_Music:
Originally posted by kyebosh:
Well no not quite the same, the dof will be different (more DOF for the 1.6x crop).
That is
if you shoot with the same settings and distance with a 100 on 1.6x vs a 160 on FF. |
This is not true. For the same reproduction ratio, at a given physical aperture, DOF is identical regardless of the focal length of the lens. At a 1:1 reproduction ratio, my 60mm macro has exactly the same DOF as a 105mm macro lens. I used to believe what you are saying here (essentially, that a 60mm macro lens would have more DOF than a 105mm macro lens), but it turns out not to be true.
R. |
Robert is correct. For any given focus distance, the lens with a shorter focal length will have a greater DOF than one with a longer focal length. But for any given magnification the DOF will be identical. |
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02/07/2006 07:11:14 PM · #23 |
Originally posted by ElGordo:
Robert is correct. For any given focus distance, the lens with a shorter focal length will have a greater DOF than one with a longer focal length. But for any given magnification the DOF will be identical. |
Not only that: if you crop IN on the wider view to duplicate the narrower view, the DOF in that area will be the same, assuming the point of absolute focus was the same in each image.
R.
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02/07/2006 07:16:28 PM · #24 |
| I'm pretty sure that laser eye surgery, like its precursor operation radial keratotomy, reshapes the cornea, and does not affect the lens of the eye at all. However, the optical principles involved remain the same. |
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02/07/2006 07:18:09 PM · #25 |
scalvert is exactly right. Although one please don't mis-understand the "cropped AND magnified" comment; which is true. However the image WxL of the amaller digital has too be "magnified" to get the same appearant "printed" photo size. Thus his comment.
If it were even a sliver of possible, a film based camera (and its lens) were adapted originally to the digital world, a full frame 1Ds would not be $8,000 and have a purpose. If you could get the even a more mag'd image with a small cheaper lens - how could that be not the sales item of the world...
The fact was, they physically couldn't get the electronic traces required to have the pixels tight enough on a full size sensor AND keep it repeated in mfg AND cost effective enough too sell! Otherwise they'd made a full size 35mm, fully compatible image that would replace film at the conception.
It all gets down to the cost to repeat a piece of silcone wafer without defects and to "photographically" etch the surace perfect enough for reliable electronic currrent - over and over... Kinda like cutting diamonds, some are better than others, the big clear perect ones COST dearly!
There is a thousand tangents here, from reflected light, that which is transmited, refracted, all the ay to the partical of a photon itself. But not everyone has a masters in mechanical physics.
There is a great book called "LIGHT, Science & Magic" by Fil Hunter and Paul Fuqua. It explains the elemental factors of light, all the way too lenses, and how they work together.
Digital cameras "do nothing magic" with the light rays through an identical lens, no matter how you see it!!!
And just as a noval thought, they don't call it "Focal Length" or 35mm equivalent too for nothing!
BTW: DOF is "only" related too a lens system and not a camera whatsoever. You can not vary the DOF from a single lens no matter what you mount it on! |
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