Digital Camera Equipment. THE Help and discussion thread.

[Peetabix]

No what I meant was it wasn't a necessity to have a lens at £xxxx the same as it isn't a necessity nowadays to take amazing pictures.

[Sharon]

Also 24mm on a cropped sensor body

I'm taking notes here.... but what is a cropped sensor body, and why does that sound like a bad thing?

[Peetabix]

Read here http://www.cambridgeincolour.com/tutori ... r-size.htm and use the wee calculator 1/4 way down the page to see how the 24mm lens will be affected on a cropped sensor body.

I've said cropped so much to myself in the last 5 minutes my brain does not recognise it anymore.

[scotgio]

Also 24mm on a cropped sensor body

I'm taking notes here.... but what is a cropped sensor body, and why does that sound like a bad thing?

It's not necessarily a bad thing - you just need to keep it in mind when looking at lenses. The value of full frame sensors is often overstated, there is nothing magical about the 35mm format size. Indeed the only reason it was adopted 50 odd years ago was for convenience, it allowed the construction of smaller cameras. The sensors in most digital SLRs are smaller than a 35mm negative, as a result the view through the lens is in effect 'cropped.' This means a 17mm lens will give the same field of view as a 28mm lens.

This actually does have some major advantages - cropped sensor cameras only use the sweet spot of the lens. Camera lenses are sharpest at the center, sharpness falls off often quite sharply as you reach the edges of the lens. A cropped sensor camera only uses the middle section of the lens to gather image forming light. You also get a nice boost with telephoto lenses, my 70-200 effectively becomes a 112 to 320mm. The only real downside to cropped sensors is it is far more difficult to get good quality ultra wide lenses.

Simply put, multiply the focal length of the lens by 1.6 if a Canon or 1.5 if a Nikon to get the 35mm equivalent focal length. Therefore 24mm on a 450D will give the same field of view as a 38mm lens on a traditional 35mm body. This is quite a narrow FOV, many people like to have at least a 28mm equivalent in a walkabout lens (i.e. at least 18mm at the wide end on a 450D). As I recommended previously, the 17-40 F4 L is a nice fit here, and I still reckon the 24-105 is a much better bet if you don't mind the 24mm.

[potatojunkie]

It's not necessarily a bad thing - you just need to keep it in mind when looking at lenses. The value of full frame sensors is often overstated, there is nothing magical about the 35mm format size. Indeed the only reason it was adopted 50 odd years ago was for convenience, it allowed the construction of smaller cameras. The sensors in most digital SLRs are smaller than a 35mm negative, as a result the view through the lens is in effect 'cropped.' This means a 17mm lens will give the same field of view as a 28mm lens.

There's nothing magical about the 4X5" format size, but it produces higher quality images than 35mm. In my (admittedly limited) experience, full-frame sensors produce higher quality images than cropped sensors. Full-frame sensors tend to have larger photosites, which collect more photons per pixel, leading to a slightly more favourable signal-to-noise ratio. This is why, say, the 5D perfoms so much better at high ISO values than the 400D.

Here are some horrible test images. I might take the time to do this properly later on, as it's the sort of thing that interests me.


400D, ISO 1600, f/4, 1/50s, 24mm


5D, ISO 1600, f/4, 1/50s, 24mm

Both shots were taken at approximately the same distance from the wall. The field of view crop is somewhat exaggerated at wider angles.

Here are a couple of 100% crops from the original files:


400D (unprocessed)


5D (unprocessed)


400D (via Photoshop and Lightroom)


5D (via Photoshop and Lightroom)

The 5D is 12-and-a-bit megapixels to the 400D's 10-and-a-bit, which is as near as makes no difference in terms of resolution. Furthermore, the 5D is a year older than the 400D, and newer cameras have all sorts of clever noise-reduction technology built in. Nevertheless, the 5D still produces cleaner images and picks up more detail (notice the ribbing on the sides of the lantern, not present in the 400D.

Whether you'd notice this in anything other than barn-door-sized prints is another matter entirely, of course.

This actually does have some major advantages - cropped sensor cameras only use the sweet spot of the lens. Camera lenses are sharpest at the center, sharpness falls off often quite sharply as you reach the edges of the lens. A cropped sensor camera only uses the middle section of the lens to gather image forming light. You also get a nice boost with telephoto lenses, my 70-200 effectively becomes a 112 to 320mm. The only real downside to cropped sensors is it is far more difficult to get good quality ultra wide lenses.

Not as much of an advantage as it first appears. Here's why:


5D at 200mm, note falloff at corners.


400D at 200m, same lens, same settings.


5D image cropped to match the 400D

These have all been resized—the cropped image from the 5D is smaller than the same shot from the 400D. But it's still sharper.

Here's a full-sized crop from the 400D:


A full crop from the 5D, smaller but better resolved:


(these were shot through a grubby window, which I wasn't for opening, because it's baltic out)

If I haven't yet bored everybody to tears, I'll try and get some test shots demonstrating the differences in how cropped and full-frame sensors record subtle colour variations and tonal gradiations, and how the field of view crop alters depth of field. Essentially, cropped sensors produce more depth of field at a given aperture and perceived subject distance than full-frame, which can be a good or a bad thing depending on what you're up to. For instance, f/2.8 on the 5D looks about equivalent to f/1.8 on the 400D.

I've also just given myself a headache walking about with two cameras clapped to my face, with one eye looking through each viewfinder. The viewfinder on the 5D is brighter, clearer, and much larger, and makes using the viewfinder on the 400D feel a little like peeping through a hole in a fence.

[scotgio]

[In my (admittedly limited) experience, full-frame sensors produce higher quality images than cropped sensors. Full-frame sensors tend to have larger photosites, which collect more photons per pixel, leading to a slightly more favourable signal-to-noise ratio.

Of course you are correct in this comparison between the cameras you've shown, but my point was it is not the format size which is responsible for the difference in image quality you are observing here. It is as you observe photosite pitch, in addition to the sensor design (CMOS or CCD etc) as well as the post processing applied from the camera (even when shooting RAW the camera will still apply some internal noise reduction algorithms).

To be honest the photosite argument which people often use is getting less and less relevant, the 5D mk II has 6 nanometer photosites vs the 5D's 33% larger 8nm photosites yet the 5d mkII delivers cleaner high ISO images. Advances in sensor design and camera processing so far are usually mitigating any negative effects from reductions in photosite size, particularly in Canon models. Photosite size comparisons would only be valid where you could guarantee the same sensor design was used, which is impossible given how secretive camera manufacturers are about their tech. Its kind of like the age old MHz myth, you can't compare processors of different types by MHz alone and you can't compare camera sensors by photosite size alone to ascertain image quality. It's only one factor.

Furthermore all these factors are completely independent of format size. An APS-C sensor can still theoretically provide the same level of image quality (although possibly at slightly lower resolutions with current tech to allow for an increase in photosite size). Like I said, the 35mm format size has nothing to do with this, although with current crop of DSLRs full frame cameras typically do provide better image quality.

If I haven't yet bored everybody to tears, I'll try and get some test shots demonstrating the differences in how cropped and full-frame sensors record subtle colour variations and tonal gradiations

Again this has nothing to do with the format size! This is purely a result of the more expensive sensor designs manufacturers put in their full frame cameras, as well as differences in processing. Typically full frame cameras record 14bit images, most cropped sensor cameras only record 12 bit images - this is generally a limitation of the processor used (Yes raw files always show up as 16 bit in image editors, but only 12 or 14 bit colour depth is ever actually recorded in the file). This often accounts for better gradiations in tone and shadow detail, but is completely independent of the sensor's size. Simply, full frame cameras cost more, and naturally manufacturers will give you better kit for your money.

The size or shape of a sensor is irrelevant for IQ purposes. You could make a star shaped camera sensor the size of a finger nail from the same silicon wafers used for the 5D and get the exact same image performance, just at a lower resolution. Heck stick a lomo sticker on that and you've probably got a surefire sales success!

This is all very boring, and sadly very irrelevant. 'Pixel peeping' is a filthy habit that I too am guilty of. Get something that you like the feel and handling of, and that you'll be confident you'll have on you should a photo op arise. Any photo is better than no photo at all, and something that you enjoy using is better than the greatest camera ever made if you don't enjoy using it!

[scotgio]

These have all been resized—the cropped image from the 5D is smaller than the same shot from the 400D. But it's still sharper.

There's clearly other factors at work here, a difference in sharpness like this should most certainly not occur - in fact the 400D looks like there has been some camera shake or a misfocus. Where both these shots taken from a decent tripod? Other than that, good comparison!

[Lucky Poet]

Interesting comparison all the same. I agree about viewfinders - my k20's got a good clear viewfinder so far as APS-C jobs go, so I hear, but it's shown up big time by my da's old late 60's 35mm. (I'm assuming full-frame DSLRs match film SLRs in this, mind you...)

Related to all this, I was reading an interesting thing the other night that argued Leicas were a second-best option when Cartier-Bresson started using them in the 30s - and that 35mm film itself was widely seen as an amateurish and limiting format until the 50s - auld Henri was ahead of his time in that, apparently. Then again, he wasn't short of a bob or two either.

http://theonlinephotographer.typepad.co ... pness.html

[potatojunkie]

Of course you are correct in this comparison between the cameras you've shown, but my point was it is not the format size which is responsible for the difference in image quality you are observing here. It is as you observe photosite pitch, in addition to the sensor design (CMOS or CCD etc) as well as the post processing applied from the camera (even when shooting RAW the camera will still apply some internal noise reduction algorithms).

To be honest the photosite argument which people often use is getting less and less relevant, the 5D mk II has 6 nanometer photosites vs the 5D's 33% larger 8nm photosites yet the 5d mkII delivers cleaner high ISO images. Advances in sensor design and camera processing so far are usually mitigating any negative effects from reductions in photosite size, particularly in Canon models. Photosite size comparisons would only be valid where you could guarantee the same sensor design was used, which is impossible given how secretive camera manufacturers are about their tech. Its kind of like the age old MHz myth, you can't compare processors of different types by MHz alone and you can't compare camera sensors by photosite size alone to ascertain image quality. It's only one factor.

See, my contention is that all other things being equal, a larger format sensor will produce higher quality images. I'm aware that in the real world you won't ever find that equal footing. The fact remains that the 5DmkII would produce images of even higher quality had the designers not been hampered by the race for more megapixels.

Furthermore all these factors are completely independent of format size. An APS-C sensor can still theoretically provide the same level of image quality (although possibly at slightly lower resolutions with current tech to allow for an increase in photosite size). Like I said, the 35mm format size has nothing to do with this, although with current crop of DSLRs full frame cameras typically do provide better image quality.

For a given resolution, a larger sensor will have larger photosites. Larger photosites gather more light. A higher sampling rate leads to more signal, less noise. There's a direct correlation between the size of the sensor and the quality of the images it will produce.

If I haven't yet bored everybody to tears, I'll try and get some test shots demonstrating the differences in how cropped and full-frame sensors record subtle colour variations and tonal gradiations

Again this has nothing to do with the format size! This is purely a result of the more expensive sensor designs manufacturers put in their full frame cameras, as well as differences in processing. Typically full frame cameras record 14bit images, most cropped sensor cameras only record 12 bit images - this is generally a limitation of the processor used (Yes raw files always show up as 16 bit in image editors, but only 12 or 14 bit colour depth is ever actually recorded in the file). This often accounts for better gradiations in tone and shadow detail, but is completely independent of the sensor's size. Simply, full frame cameras cost more, and naturally manufacturers will give you better kit for your money.

Except! The 5D, being rather long in the tooth, produces the same 12-bit .CR2 files as the 400D. It just sacrifices less colour detail to in-camera noise reduction.

This is all very boring, and sadly very irrelevant. 'Pixel peeping' is a filthy habit that I too am guilty of. Get something that you like the feel and handling of, and that you'll be confident you'll have on you should a photo op arise. Any photo is better than no photo at all, and something that you enjoy using is better than the greatest camera ever made if you don't enjoy using it!

Aye. In saying all this, I've made 20X30" prints from files I shot on a Sony H1, a 5.1MP prosumer compact with a sensor with something like a 6X crop factor, and they looked braw[1]. Far more to do with being in the right place (in front and a little to the left of Alan Rickman) at the right time (just as he pulled this wee pensive expression, for a split second) than the machinery involved.


[1]Personal opinion, but I have sold a couple.

[Squigster]

Until now I've always used a bog standard digital camera, but i'm thinking about taking the plunge into the world of DSLR.

My preferred option as a starter kit is: Pentax K200D Digital SLR Camera with 18-55mm Lens and 50-200mm Lens - £465

http://www.warehouseexpress.com/product/default.aspx?sku=1024916

Your opinions are invited

Cheers

Squigster

[frazzmac]

Until now I've always used a bog standard digital camera, but i'm thinking about taking the plunge into the world of DSLR.

My preferred option as a starter kit is: Pentax K200D Digital SLR Camera with 18-55mm Lens and 50-200mm Lens - £465

http://www.warehouseexpress.com/product/default.aspx?sku=1024916

Your opinions are invited

Cheers

Squigster

Squigster, I'm not really a font of knowledge on the pros and cons of particular models. Two suggestions though. Firstly, try to get your hands on a couple of different cameras to find one you can be comfortable holding (yes, really). Also, only get one lens to start with. Play with the camera for a couple of months, then think about buying other lenses once you've built up some experience.

frazz

[Squigster]

Cheers for the advice Frazz

[Lucky Poet]

I'd agree about getting the single 18-55 lens kit first, to get used to the camera and get an idea what you want to do with it next by way of a second lens. Holding various cameras before buying is a good idea too, though I must admit I never did.

The k200 seems an excellent camera though, a kind of supercharged update of my first DSLR (the venerable k100). I don't want to come across as a Pentax fanboy, but I don't think you'd go far wrong with one.

[Fossil]

Until now I've always used a bog standard digital camera, but i'm thinking about taking the plunge into the world of DSLR.

My preferred option as a starter kit is: Pentax K200D Digital SLR Camera with 18-55mm Lens and 50-200mm Lens - £465

http://www.warehouseexpress.com/product/default.aspx?sku=1024916

Your opinions are invited

Cheers

Squigster

aye! I've had my aye on that camera since it came out last year.

[AlanM]

The great thing about the Pentax is that it can use loads of the old manual focus Pentax K-mount lenses

The Sony's can use old Minolta AF lenses or m42 mount lenses with the adapter.

The bargain DSLR of the moment has to be the Sony A200 at under £250 with the 18-70mm kit lens