Size Matters? I'd like to take a moment to talk about it.

[TheAnimus]

We see postings all over the internet, with people saying sensor size matters, you should buy a full frame. This irks me, and whilst waiting for this code to test I decided to try and explain it a bit better.

First off, what was true 3-5 years ago is not now. The gap between sensor size and quality is closing rapidly. If you think 35mm, a format which is a legacy from cinifilm (no engineer ever said "Yes thats optically perfect!") just so happens to be the best size out there, your deluding yourself. Sure before the dslr revolution, 35mm made sense as there was a glut of quality lenses already available, today, you don't have to be FF for top quality glass. Lets try and figure out why FF isn't always best, and why snobbery about it is stupid.

I'm going to assume everyone is happy with the relationship of ISO to EV. If your not, you can google it, or take my word for the workings.

Stealing a lot of images from neocamera: http://www.neocamera.com/camera/olym...es/comparative
They did a compartive shot set between a:
Olympus OM-D E-M5, Pentax K-5, Nikon D4
they are
Micro 4/3rds, APC-S and Full Frame sensors retrospectively.

The results are really interesting, most of the time, each sensor lags behind the other in noticable quality, by one stop.

When comparing the D4 at 800 ISO to the K-5 at 400 ISO to the E-M5 at 200 ISO, the differences are rather slight. Granted the FF does still have the edge when looking at the results diagonally, but not by *that* much, when you consider the downside of cost and weight.

But this becomes really fun, when we start talking about DoF, after all, with that 1EV difference, we know the smaller sensor would have a larger DoF. When taking pictures in low light, needing a higher ISO, I've never found myself wishing I had less DoF, because normally I'm going as wide as I can without loosing detail, to keep the ISO low.

How about a worked example?

Well pretend we've got a 5DmkIII, we've got some people 1m away, we want the group in focus, its dark so we're at ISO 3200 shooting f2.8 on a 55mm lens, we've got about a DoF of 5.3cm. It's a tight squeeze but its OK. So what about a APC-S? Well we can actually go down (at the same effective focal lenth) to f1.8, to yeild more DoF, in fact 5.45cm. Of corse, as we all know f2.8 is actually more than 1 EV. So we might even be able to use ISO1200 instead.

Sensors are evolving so fast, what was the best in FF yesterday, is now achiveable in micro four thirds size today.

Comapre this to glass, we've seen little if any innovation in lenses, the closest would be image stablisation, which is a contentious topic as they generally show no benefit over in body.

So the upshoot is buy good glass, spending £2k on a camera, and having only two or three good lenses is stupid. If you've got the few k to burn, sure it will be good quality, but if you want the best don't kid yourself, FF isn't as good as larger. Can the £1.5k price difference be justified by quality alone? Often not as the worked example above shows. Consider what would be your options if you'd spend the money on glass instead!

[kalniel]

Well it's about the extremes that the shift in working focal length/ISO afford you. But I completely agree. FF is the best choice for pap shots while smaller sensor cameras can make very high quality macro or landscape shooters.

But then I shoot Oly, so I've already been convinced that it's better to use a sensible sensor size (and shape!) that enables telecentricity and getting the best out of the glass

[CAT-THE-FIFTH]

Its all about balance,but the problem is people tend to want to focus on one big number to indicate how "good" something is it seems. Even the 36MP sensor in the D800 actually has the same photo-detector surface area as the on in the D7000,so it has no advantage in this area either.

However,MP number is also not everything and the Foveon sensors demonstrated this,as even with their "low" MP rating pictures could be printed much larger than with traditional sensors of the same MP rating using a Bayer mosaic filter and even with a lot of sensors used in space,the images tend to be a mosaic combining the primary colours.

The current Foveon sensor when matched with a good lens is pretty impressive:

http://www.magezinepublishing.com/eq...1345814283.jpg

http://www.magezinepublishing.com/eq...1345814256.jpg

That is RAW conversion from a 14MP DP2 Merill compact which has a 50MM lens. It is a real shame that no other companies are developing Foveon type sensors apart from Sigma.

I think the main advantage for the high MP 35MM frame sensors is if you want high MP super wide angle shots,or want wide angle tilt/shift lenses. Even the latter is down to the fact that there are no APS-C tilt/shift lenses.

[Bobster]

you understand that DoF does not increase or decrease depending on sensor size?

[TheAnimus]

You understand thats not true. You know about the Circle of Confusion right? Which for people who lack a maths background is confusing*

Did you read my worked example? Is my maths not correct?

Same distance to subject.

Adjust focal length for the crop factor of sensor.

Oh lookie, more DoF.

It is about taking the exact same photograph. As we all know from the DoF equation, you can either change the f stop, the distance from subject, the focal length. So if you want to keep the exact same lens for arguments sake, then you have to step further back by the amount of the crop factor, and oh, again, my example holds.

*Many engineers consider such things important.

[TheAnimus]

I think the main advantage for the high MP 35MM frame sensors is if you want high MP super wide angle shots,or want wide angle tilt/shift lenses. Even the latter is down to the fact that there are no APS-C tilt/shift lenses.

Yeah wide angles are easier with a larger sensor, but there are obvious trade off in glass production, that limit how large one should go.

It is a real shame that no one really (other than sigma) is doing anything other than bayer, because ultimately it will allow for a much higher density with far greater sharpness and accuracy.

In fact it is very possible that such alignments will allow for far greater image quality shift than sensor size could ever allow. Sadly, I think too many people who like to think of themselves as professional won't buy in to a technology shift.

[Bobster]

right, you're adjusting the focal length - but using the same lens same distance = same DoF..

[TheAnimus]

No, it will be different thanks to Circle of Confusion, but minimally so.

The thing is your using capturing the same image, with differing sensor sizes, you can't use the same focal length and distance. Which is the point. One has to change.

Again, notice the phrase "effective focal length"

Are you saying that changing the focal length or distance to subject is deal breaker or somethign?

[Butcher]

Full frame? Bah get a medium format!

[KeyboardDemon]

I remember discussing something like this at Uni years ago, only then we were talking about the issue in relation to film and I really don't remember enough about it now, but we looked at images of the same scene taken using a 50mm lens with a 35mm camera, then on a camera using 120 roll film, 6x7 and then 5" by 4". I think it the conclusion we came to was that it boiled down to the relationships between the size of the lens and the angle of view and how this changed as result of changes in the film size, which I think was referred to as the golden ratio. I think for a 6x7 camera to take a near identical picture to a 35mm camera with a 50mm lens you would have to use a 90mm lens to get the same angle of view.

As I recall the issues we discussed were to learn about the golden ratio and that 50mm lenses were used as the 'standard' lens on 35mm camera because of this calculation, therefore if you change the size of the sensor you would also have to change the lens to create that same angle of view.

I read this yesterday and spoke to a friend of mine who works as a professional photographer and he said there are many cameras with different size sensors that could produce professional quality results but he would still opt for a DSLR with a 35mm sensor, not because of the sensor, but because of he thought it would be more capable of surviving a longer duty cycle, at least more so than a cheaper camera with smaller sensors. Essentially, he was saying that he feels that first and foremost a full frame DSLR will be the more reliable choice, then lenses are the next most important consideration and sensor size for him is way down the list of priorities when selecting new hardware.

[CAT-THE-FIFTH]

Full frame? Bah get a medium format!

Medium format is for amateurs,10X8 all the way!!

[TheAnimus]

Essentially, he was saying that he feels that first and foremost a full frame DSLR will be the more reliable choice, then lenses are the next most important consideration and sensor size for him is way down the list of priorities when selecting new hardware.

Yes even as a hobbiest I think build quality is incredibly important, that might be because I do like to try and travel. But I think the the reason full frame devices are more reliable is simply the cost, the quality of the shutter assembly, afteral shutters are what normally fail. With sealing to help prevent nasty stuff getting in which can degrade quality or even create issues for the mechanical parts.

What I am more trying to address here, is the idea that your not a "pro" without a full frame body for image quality, as there are many environments where it won't really help. If your in a well light place, then full frame won't offer as good as medium.

I also want a Sigma DR2, but they just cost too much, eat batteries etc.

It also shows that the march of progress in bodies is great, that investing in glass is a good idea, spending a lot of money on a body is stupid unless you've got an awful lot of money to spend.

For people who are worried about failure, what most do in technology is have redundant backups. When the technology of the device is aceptable, rather than spend thousands more, simply buy lots of the cheaper ones.

[CAT-THE-FIFTH]

I also want a Sigma DR2, but they just cost too much, eat batteries etc.

The sensor and lenses in the DP Merill range are impressive,however,the cameras are somewhat clunky to use. Funnily enough a reviewer considered it more like using a film camera of sorts. It will be interesting to see how they stack up against the Fuji X100S which uses an improved version of the sensor in the X-Pro1,and the Leica X2 although both will cost more,so I suppose this is who Sigma are pricing the cameras against I suspect.

However,this price for the original X100 looks quite good:

http://www.cliftoncameras.co.uk/Fuji_X100_Finepix