PDA

View Full Version : Crop factors




whocares
Dec 28, 2005, 07:44 PM
No, that's not a typo in the title ;)

Question is simple: what do you think about the full-frame versus x1.3/x1.5 sensors debate in DSLR. I prefer the Nikon sized x1.5 and know that some here prefer full-frame. So let's chew over this a bit and figure out that nobody's wrong. :)

I'll start. I prefer x1.5 because:
* I don't really see the point of a 24x36 mm sized sensor in the first place (IIRC it was originally designed to accomodate Kodak's slide mounting machine)
* I makes for easier to design/smaller/cheaper lenses - especially at the lower focal lengths
* you win quite a few mm for your telephoto w/o the use of teleconverters (a 300 f/2.8 magically "becomes" a 450 f/2.8)
* they're way cheaper
* you can stack insane amounts of filters on full-frame lenses w/o fear of vignetting; and, you can use full-frame lenses at full aperture with less vignetting
* you can get greater reproduction ratios with macro lenses.

Of course full-frame does have some advantages:
* you don't loose your wide-angle lenses (but see point 2 above)
* you potentially have less noisy sensors (bigger "pixels" = more light per "pixel" = less noise).

What do you all think/like/prefer and why?



bousozoku
Dec 28, 2005, 08:18 PM
I like my Olympus made-for-digital lenses because they are smaller than the equivalent 35mm lenses, using a 2x conversion factor.

3 lenses (14-54mm, 50-200mm, and 50mm macro) do pretty much everything I need except the extreme reaches.

Since they are part of an all-digital system, they work quite well and there is no guess work as there is with using 35mm lenses on various converted-for-digital bodies.

ksz
Dec 28, 2005, 10:15 PM
I tend to agree with the DX camp. If lenses can be made smaller, lighter, and cheaper without affecting image quality, then I think we have made progress. Large bulky lenses are necessary for f/2.8 and f/1.8 for full frame, but this can limit the practicality of those lenses. The dimensions of full frame are arbitrary, and there is no reason why a different frame size cannot or should not be used.

Today's sensors are good, but not as good as they should be. While there is an inverse relationship between noise and pixel size (and a direct relationship between sensitivity and pixel size), this is a momentary technical problem that can and will be overcome.

Here is a recent article about emerging advances in sensor technology:

From http://www.dpreview.com/news/0512/05121201new_chips.asp

The first technology being developed integrates an oversampling "sigma-delta" analog-to-digital converter at each pixel location in a CMOS sensor. "CMOS" is a common semiconductor fabrication process used in most chips manufactured today. Previous attempts to do this on-pixel conversion have required far too many transistors, leaving too little area to collect light. The new designs use as few as three transistors per pixel, reserving nearly half of the pixel area for light collection. First tests on the chip show that at video rates of 30 frames per second it uses just 0.88 nanowatts per pixel--50 times less than the industry's previous best. It also trounces conventional chips in dynamic range, which is the difference between the dimmest and brightest light it can record. Existing CMOS sensors can record light 1,000 times brighter than their dimmest detectable light, a dynamic range of 1:1,000, while the Rochester technology already demonstrates a dynamic range of 1:100,000.

Traditional image sensors use an array of light-sensitive diodes to detect incoming light, and transistors located at each photodiode to amplify and transmit the signal to an analog-to-digital converter located outside of the photodiode array. Other designs can convert the signal to digital at the pixel site, but require high precision transistors, which take up considerable chip space at each pixel and reduce the amount of surface area on the chip devoted to receiving light. The new design not only uses smaller transistors at each pixel, and thus can allow more light to be detected, but the transistors can be scaled down in size without diminishing the sensor performance as advances in semiconductor fabrication technologies allow the size of transistors to shrink. This means that much denser, higher-resolution chips can be developed without the prohibitive problems of the existing sensor designs. When transistors are reduced in size, they also become faster, allowing incoming light to be sampled more frequently and accurately.

njmac
Dec 29, 2005, 09:31 AM
No, that's not a typo in the title ;)

Question is simple: what do you think about the full-frame versus x1.3/x1.5 sensors debate in DSLR. I prefer the Nikon sized x1.5 and know that some here prefer full-frame. So let's chew over this a bit and figure out that nobody's wrong. :)

I'll start. I prefer x1.5 because:
* I don't really see the point of a 24x36 mm sized sensor in the first place (IIRC it was originally designed to accomodate Kodak's slide mounting machine)
* I makes for easier to design/smaller/cheaper lenses - especially at the lower focal lengths
* you win quite a few mm for your telephoto w/o the use of teleconverters (a 300 f/2.8 magically "becomes" a 450 f/2.8)
* they're way cheaper
* you can stack insane amounts of filters on full-frame lenses w/o fear of vignetting; and, you can use full-frame lenses at full aperture with less vignetting
* you can get greater reproduction ratios with macro lenses.

Of course full-frame does have some advantages:
* you don't loose your wide-angle lenses (but see point 2 above)
* you potentially have less noisy sensors (bigger "pixels" = more light per "pixel" = less noise).

What do you all think/like/prefer and why?


I would love to hear from someone who has experience with full frame DSLR and cropped sensor DSLR. I can only accept the crop because I can't afford the full frame. I just assumed that full frame was, of course, better. You put up good arguments for the cropped sensor though :cool:

sjl
Dec 29, 2005, 04:48 PM
Question is simple: what do you think about the full-frame versus x1.3/x1.5 sensors debate in DSLR. I prefer the Nikon sized x1.5 and know that some here prefer full-frame. So let's chew over this a bit and figure out that nobody's wrong. :)

When you get right down to it, it's something of a wash. There are situations where full frame is advantageous; there are situations where a cropped image is advantageous. It's all about what you want to do with the camera.

As an extreme case, consider the Hasselblad body. 22 MP(?) in a medium (or was it large?) format sensor. Fantastic for taking high resolution, very wide angle shots for (eg) advertising purposes. Massive overkill for your typical point and shoot amateur.

If you like taking wide angle pictures, the larger the sensor, the better: it's easier to take ultra wide angle shots if you're using a large image area, and I'd imagine it'd be easier to design the lenses at that extreme for a large sensor area (note that I'm no optics expert, so this is a wild guess on my part.) If you like taking nice and zoomy pics, on the other hand, the cropped image is an overall win.

The other question is: are the lenses you want to use available? For example, Canon's fisheye only works effectively on a full frame sensor; the EF-S cameras (and the 1D series to a lesser extent) crop out the areas where the effect is most noticeable. Nikon, on the other hand, makes a fisheye to suit the cropped sensor (they almost have to, since they don't make a full frame body.)

Figure out what you want to do with your photography, and buy a body and lenses to suit, is the aim of the game. Anything else is wasting your money.

(For the record: I have a Canon 20D, with a 1.6 crop factor. This suits me fine, and that in large part can be attributed to the extra cost for the 5D. No way could I even dream about the 1Ds.)

Chip NoVaMac
Jan 13, 2006, 09:32 PM
In regards to the original post: There has always been debate as new formats made their way in to photography. 11x14 and 8x10 "view cameras" were the norm in the early days of paper negatives. This gave way to 5x7 and 4x5 film view cameras. There was a great cry from these folks when medium format film made its debut. And the cry was made when 35mm started to take hold.

The popularity and longevity of the 35mm format is why there is great angst with the smaller digital sensors. Add to that the high cost of going digital until recently in the interchangeable lens market.

Here I go again with the same words repeated here time and again, cameras are tools. As tools you select the ones that will do the job best for you.

It all has to do with field of view. You can take a "normal" lens (generally accepted as 50mm for 35mm, 80mm for medium format, and the 1.5x factor DSLR at about 30mm). Focus at lets say ten feet at f/2.8. The depth of field will be greater for as you move from medium format to 35mm to the DSLR (in this case). Each will have their own need for either greater DOF or less DOF. Hence the right tool for the job.

And in simple terms the size of the digital sensor is sort of like different film format sizes. The larger the sensor at an equal megapixel count, the better the results. Also less noise, and noise is like grain in film

The full frame sensor camera is the Holy Grail for many photographers from a cost savings stand point. They don't want to be forced to buy a 12-24 lens to replace their 17-35. Who can blame them. But many of those that I have read wanting a 35mm sized sensor look only at the lens equation. I seldom here from most that they want to be able to limit the DOF as they are used to in 35mm film.

These few comments for a 35mm sensor are from people like myself perhaps that use RF cameras, and use DOF as part of the composition. Much like those photographers that waiting to plunk down $10-20K for the newest digital medium format cameras from Mamiya and Hasselblad.

I like my Olympus made-for-digital lenses because they are smaller than the equivalent 35mm lenses, using a 2x conversion factor.

3 lenses (14-54mm, 50-200mm, and 50mm macro) do pretty much everything I need except the extreme reaches.

Since they are part of an all-digital system, they work quite well and there is no guess work as there is with using 35mm lenses on various converted-for-digital bodies.

The Olympus 4/3 system is probably the best overall design for the DSLR. First is that all their lenses are designed for digital. Meaning that the light rays are "focused" to fill each photo receptor on the CCD.

And compared to comparable 35mm lens in focal length range and speed, they are smaller. Even their newest f2.0 lenses are of equal size and weigh to the similar equal focal length lenses from Nikon or Canon.

I would love to hear from someone who has experience with full frame DSLR and cropped sensor DSLR. I can only accept the crop because I can't afford the full frame. I just assumed that full frame was, of course, better. You put up good arguments for the cropped sensor though :cool:

I have played with the Canon 5D at work. Thought about buying one. Decided not to at this point. The reason is that I am a wide angle field of view type photographer. And the edge sharpness with FF digital with ultra wide angles is not where I would want it to be.

There is a great advantage in using 35mm lenses on cropped field of view DSLR's. And that is that we end up using the sweet spot of the lens. Lenses are inherently sharpest in the center.

In ultra wide angle photography at this point a decent FF sensor and lens would limit the distortions that we see in many of the wide angle digital specific lenses. The laws on optical design are pretty tough.

Hope some of this helps, albeit a bit late.