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09-27-2013, 04:05 PM   #256
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QuoteOriginally posted by regor Quote
To add to your point. F4 is F4 and the DOF at F4 at a given FL is always the same on FF as it is on APS-C. What changes, and the only thing that changes, is the Field of View. To say that DOF is shallower on FF is a mis-conception. What causes the apparent "greater DOF" of APS-C is the use of a shorter FL on APS-C necessary to get the equivalent FOV obtained on FF at the same distance from the subject. Crop a FF image to the FOV of APS-C, they will have exactly the same DOF. Walk away from the subject with an APS-C subject to obtain the same FOV at the same FL as FF, and the DOF will still be exactly the same; however, the perspective will be different, hence the only difference between FF and APS-C is the combination of DOF for a given perspective (which is controlled by distance from the subject). In theory, take portrait as an example, a full head image taken with a 70mm on APS-C, will be better than the same image taken with a FF camera as you need be closer to the subject, hence introducing more distortion ! In this case, APS-C is actually better than FF as you can work further away from the subject ! Work from the same distance with a FF + 105mm lens, and you'll end up with the same perspective with less DOF and less resolution perhaps (perhaps too little even). So which is best ? Neither, they are just different, and you learn to work with the differences !

addendum:

Conclusion: At equal Field of view, you could never reproduce the qualities of a 105mm + FF with and APS-C sensor, nor could your reproduce the qualities of a 70mm + APS-C with a FF sensor ! What advantage FF has comes with the design of the 50mm FL, which for some reason happens to have the highest resolution of all FLs. The combination of FOV + DOF + RESOLUTION which is optimum at the same magnification as the human eye makes it a winning combination.
Thanks for that explanation. I'm sure someone will argue with you about something but I think I finally understand this. I've been trying to for about a year and every time I see an explanation that I think makes sense it makes my brain hurt. I think I actually understood it this time. I'm copying this and putting it on my bulletin board so I can read it every day......

09-27-2013, 04:08 PM   #257
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QuoteOriginally posted by derekkite Quote
Isn't the advantage of a larger sensor more apparent when you want wide angle? To get wide with aps-c you need 12-15mm, with all the inherent distortions that come from such a lens. With full frame you are somewhere in the 20-30mm range, with MF quite a bit longer. Of course for telephoto it works the other way; a full non cropped exposure at 300mm on all three will give you a quite a different image.

The dream machine for landscape has a large sensor. From there on you deal with compromises. Each size has it's advantages and disadvantages, and depending on what and how you shoot, they are more or less important to you.

What is the size of the aperture on an aps-c 15mm at f22 compared to a wide angle medium format lens at f22? Or a full frame one? Again, it depends how and what you are shooting.
Yes you're right, the perspective distortion is better controlled for wide angles with FF. Unfortunately contrary to my earlier argument about pedestrian lenses performing well, there is no Sigma 10-20 equivalent (value for performance wise) in FF if you need corner to corner sharpness, other than samyang 14mm, but it's MF. Even at f/8 most FF UWA doesnt' really deliver in the corners. The cheapest that have good corners is The Tokina 16-28mm at double the price of the sigma (followed by the Nikon UWA zooms and Canon's 17mmTS, all pricey). Other FF lenses even the 17-40L isn't as well designed at the sigma in the extreme corners.

This doesnt stop people from making great images with those lenses that are weak in the corners of course.... We also have the rather exotic Sigma 12-24 which at $300 used is cheaper than the Sigma 8-16mm. So you do get (way) more selection, just no cheap ticket for sharp corner-to-corner 10mm (APS) UWA in FF

Last edited by Andi Lo; 09-27-2013 at 04:13 PM.
09-27-2013, 04:10 PM   #258
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QuoteOriginally posted by nanok Quote
you will get the same expousre, by definition, yes. (this is the whole point of f-stop, iso, and shutter speed -- though shutter speed does not realy need any "help" to be transferred over formats)

edit: this might seem confusing, but think of the previous example again (croping from a "conveniently large frame"): imagine it's a 6x6 cm frame, will exposure change if i take my scisors out and crop it? of course not. you might say exposure on the photosensitive are is a facot of how much light per square inch you get, not on how much light you get in all.
This is exactly what my understanding was before I joined this conversation. thanks
09-27-2013, 04:19 PM   #259
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QuoteOriginally posted by Wired Quote
This is exactly what my understanding was before I joined this conversation. thanks
well, if it makes sense now, i feel obliged to confuse you right back :P

the problem is, to get a "similar looking image" on a larger format, you need to stick more light on that phtosensitive frame, in all (so absolute terms, say: number of photons that are "captured" by the whole frame), and strictly speaking, light is that which carries the information we need to create the image, so more light means more image, hence larger format means more details, color depth ,etc, "all else being equal". of course, all else is never equal

09-27-2013, 04:22 PM   #260
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QuoteOriginally posted by wll Quote
Does anyone have an idea what the ISO rating will be on the K-3 ?

I'm hoping that it is as good as the K-5 series is in low light, for me that is a big point.

wll
Reply to Wll: The ISO rating on my K-5 II is 51,200. I can't conceive of it being any lower than this for the K-3. ISO 51,200 is plenty high!
09-27-2013, 04:25 PM   #261
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QuoteOriginally posted by StrasburgBarry Quote
Reply to Wll: The ISO rating on my K-5 II is 51,200. I can't conceive of it being any lower than this for the K-3. ISO 51,200 is plenty high!
Whispers are, ISO 100K will be reached.
09-27-2013, 04:25 PM   #262
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QuoteOriginally posted by nanok Quote
no. please, perspective depends _only_ on distance to subject, not on lens, not on format or alignment of planets. lens specific distorsions are not part of perspective (they are part of optical aberrations )
You are right, I meant FOV.

QuoteOriginally posted by nanok Quote
i wouldn't bet on that. this has been the case so far, but keep in mind much larger sensors are notoriously bad at higher iso's (medium format).
In any case, there is one other thing to consider. Fullframe cameras are not released as often as APS-C models. So typically, APS-C cameras will have more recent sensors in them, which may close the gap. I think that's why the K-5 managed such a high score at DXOmark.com when it was first tested.

QuoteOriginally posted by nanok Quote
no. the ratio of light gathering between each "well known" apertures is 1/2, that's precisely why they are well known, and if you want to verify, you need to square them:

5.6^2/4^2
1.96000000000000000000

we're mixing units here. 1.5x crop is a linear measurement, light gathering capabilities are a factor of surface (so linear squared, one might say, except squaring the crop factor is inaccurate unless you're talking about a rectangular frame). in short, assuming the same aspect ratio, the "35mm" sensor is twice the surface of aps-c, and this is why it's usually "one f-stop away" in nearly everything (like dof at same field of view). this is also why f-numbers need to be squared to obtain the exposure ratio (they are a linear ratio between focal length and aperture size)
I know. Though a crop factor of 1.5 would result in a surface area 2.25x smaller than fullframe, instead of 2x. But yes, I am talking about a rectangular frame. I have yet to see a camera with a sensor shaped unlike a rectangle.

QuoteOriginally posted by nanok Quote
dof: no, as you see from above, it's pretty much the same (close enough it makes no difference)
comparing noise performance of ff at iso200 to aps-c at iso100 on modern sensors is a purely academic exercises imho.
For ISO 100 and 200 I might agree. But I don't like running my K-5 any higher than ISO 4000. With a comparable fullframe sensor I could go to ISO 8000.

QuoteOriginally posted by nanok Quote
all these "all else being equal" comparisons have two problems: all else is never equal, and comparative discussions might not be meaningful for practical purposes from a point on (for instance, comparing the output of a sensor like the one in the k-5 with one in a "comparable" 35mm camera, using good quality (read: excellent) glass, one might be surprised how close they will be). Technology is at a point where one no longer _needs_ bigger sensors for image quality purposes (exceptions are rare, and tend to drift towards phaseone and the likes anyhow), you might _want_ it for a bigger, brighter viewfinder, you might dream of it because you have some special pixie dust lens which only really works "properly" on a 35mm frame, or just because you can afford it. but need it? nope. sensor technology has reached "maturity" a few years ago (about the time k-5 was released), in other words. that's not to say improvements are no longer possible, but rather that you probbaly don't need them

now i should run...

ps: sorry for the rant, nothing personal, i have a compulsive reaction to misuse of the term "perspective" in particular
No problem. I have a compulsive reaction to misuse of the term "speed" for a lens. And btw, I am perfectly happy with my APS-C based system. I do acknowledge the fact that e.g. a Canon 70-200/4 would be near the same size as my 50-135/2.8, have the same FOV on fullframe, etc. But a 6D is bigger than my K-5. As I like to travel, I like to keep things small and light.

[on-topic] (at last )

As for the mighty K-3, I may buy it, or I may not. It depends, really. I do want a better autofocus system, but from what I've heard, the K-5 II already is an improvement where I want it. When the K-3 comes out, no doubt will there be a lot of people selling their K-5 II's. So I will just see if the price and specs on the K-3 are enough to make me buy it instead of such a used K-5 II. I do hope they are though.
09-27-2013, 04:27 PM   #263
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QuoteOriginally posted by filoxophy Quote
Yeesh, the whole equivalence thing comes up here almost as much as FF! How many more angles and analogies can possibly be left?
APS is like a Pegasus, Full Frame is like a Unicorn. The Pegasus is fine for a lot of situations, but if you have to open a can of beans, the Pegasus can't help you. That's when you can use the Unicorn's horn to open the can of beans.

In other words, if you have a Pegasus, you may think you are cool but you are going to starve to death. There are certain situations where there is no substitute for a Unicorn.

Make sense?

09-27-2013, 04:40 PM   #264
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QuoteOriginally posted by Andi Lo Quote
Yes you're right, the perspective distortion is better controlled for wide angles with FF. Unfortunately contrary to my earlier argument about pedestrian lenses performing well, there is no Sigma 10-20 equivalent (value for performance wise) in FF if you need corner to corner sharpness
Almost always, the corner sharpness in FF (lp/ph) exceeds that of APS-C.

It's the opposite in terms of lp/mm but I don't see why anyone should measure in lp/mm when considering resulting picture.
09-27-2013, 04:51 PM   #265
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QuoteOriginally posted by starbase218 Quote
In any case, there is one other thing to consider. Fullframe cameras are not released as often as APS-C models. So typically, APS-C cameras will have more recent sensors in them, which may close the gap. I think that's why the K-5 managed such a high score at DXOmark.com when it was first tested.
yes. that's one way how "all else is never equal"

QuoteQuote:
I know. Though a crop factor of 1.5 would result in a surface area 2.25x smaller than fullframe, instead of 2x. But yes, I am talking about a rectangular frame. I have yet to see a camera with a sensor shaped unlike a rectangle.
my mistake, i should have said "equirectangular" (square)
09-27-2013, 04:57 PM   #266
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QuoteOriginally posted by Uluru Quote
Whispers are, ISO 100K will be reached.
100k ISO is marketing gimmick. So is 51k IMHO. Nice clean ISO 3200 is just fine with me. I rarely go above ISO 400 on the k-5II, others say it is good higher than that but not for me, I struggle to keep 400 clean enough.
09-27-2013, 05:02 PM   #267
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QuoteOriginally posted by nanok Quote
you will get the same expousre, by definition, yes. (this is the whole point of f-stop, iso, and shutter speed -- though shutter speed does not realy need any "help" to be transferred over formats)

edit: this might seem confusing, but think of the previous example again (croping from a "conveniently large frame"): imagine it's a 6x6 cm frame, will exposure change if i take my scisors out and crop it? of course not. you might say exposure on the photosensitive are is a facot of how much light per square inch you get, not on how much light you get in all.
You will not get a chance to do this to any of my 120 negatives

When I use my hand held light meter it provides the same reading for my 4X5 as it does for my 135 and my iPod pinhole calculator will give the same reading for our pinhole cameras regardless of what size paper or film we load in them.
09-27-2013, 05:17 PM   #268
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Hi, gang -

Here's some info to fan the flames... I stopped in at my local camera shop today, which (as of about 1.5 years ago) did not carry Pentax. Two things:

1. They now carry Pentax! They had a full display case next to N&C, with K-5II, K-30, and one other that I can't remember...plus a full assortment of lenses and some P&S's.

2. The sales guy, who fashioned himself a Pentax aficionado, confirmed that an announcement is coming Oct 8 (without prompting). Interestingly, he said that the new body is designed to make the K-5II/K-5IIs the mid-level option. "Nearly everything" would be improved, relative to the K-5II. They'll have them in-stock around Nov 1.

I didn't have the guts to ask him about the future of FF.
09-27-2013, 05:26 PM   #269
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QuoteOriginally posted by ofer4 Quote
They'll have them in-stock around Nov 1.
Sounds good. Subject to typhoons and tsunamis in SE Asia interrupting body and lens supply, of course

But seriously, I hope Pentax can execute the K-3 introduction well. Be a pity not to have lots of stock in stores in key markets before Christmas.
09-27-2013, 05:40 PM   #270
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I just left a deposit on one....
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