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MichaelMelb_AU
18 May 2013 - 11:38 PM

Since you claim to be better than me at maths ( and I don't challenge!). - could you please explain it - how physically you get get larger DOF from, say, 50mm f1.8 DSLR lens being mounted on any CSC with a lens adapter? With maths, please Grin

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Steppenwolf
19 May 2013 - 8:01 AM


Quote: .....
There's no contradiction here. DOF depends on the lens, not sensor. The legend of larger DOF in cameras with smaller sensors stems from advertising rubbish and some practical experiences with cameras that have their lens fixed permanently. Cameras with changeable optics may have whatever DOF is required as long as a lens with suitable focus distance and aperture range may be found. And the larger the sensor is - the wider is diapason in which DOF can be controlled by the photographer. The point that smaller sensor cameras have larger DOF comes from practice the same way as "knowledge" of the Sun rotating around the Earth comes from everyday observations of it. Bleeding obvious, but wrong.

You're seriously confused. If you can't understand the reasons why smaller sensor cameras have a greater DoF (as explained above) then maybe you should try using one - it rapidly becomes very obvious.

MichaelMelb_AU
19 May 2013 - 8:08 AM

Well, if you want it done - DIY. Since I do not pretend to be particularly good in either optics or maths - I will take some help with Online DOF calculator.
With EOS 5D, 50mm f1.8 lens and 5m subject distance we have DOF=1.07m. Not much. Maybe a CSC will fare better? Let's check...
Panasonic Lumix DMC-G1 with all other equal... 0.53m! There, 2 times less! Why? It needs tighter circle of confusion of course - for this camera it's 100mm lens equivalent!
How it will do with 50mm equivqlent, i.e 25mm - 2.32m! Sure, it's what majority of people will call larger DOF.
But, EOS5D with 25mm, f1.8 and subject distance of 5m will produce whole 5.2m DOF! Sure you need to do 2X crop to get the same picture as 4/3 camera? Can we minimise the crop? Yes, we can! With a 35mm lens we get 2.27m DOF - pretty much the same as 25mm lens with 4/3 camera. And it is just 35/25=1.4 crop that would be needed to get absolutely the same result as one of the best 4/3s!
This is what I meant by creating a DOF one needs for their image. Wink

Last Modified By MichaelMelb_AU at 19 May 2013 - 8:14 AM
Steppenwolf
19 May 2013 - 1:12 PM


Quote: With EOS 5D, 50mm f1.8 lens and 5m subject distance we have DOF=1.07m. Not much. Maybe a CSC will fare better? Let's check...
Panasonic Lumix DMC-G1 with all other equal... 0.53m! There, 2 times less! Why?

Because you should be comparing the 5D/50mm lens against a G1/25mm lens. And the G1 has 2.23m DoF.


Quote: How it will do with 50mm equivqlent, i.e 25mm - 2.32m! Sure, it's what majority of people will call larger DOF.

Yes, that's what I call larger DoF. More than 2 times more! To paraphrase your statement.


Quote: But, EOS5D with 25mm, f1.8 and subject distance of 5m will produce whole 5.2m DOF! Sure you need to do 2X crop to get the same picture as 4/3 camera? Can we minimise the crop? Yes, we can! With a 35mm lens we get 2.27m DOF - pretty much the same as 25mm lens with 4/3 camera. And it is just 35/25=1.4 crop that would be needed to get absolutely the same result as one of the best 4/3s!

Wrong again. To work out the crop you need to square the focal lengths. So you need to crop by 35/25 squared - i.e. 2.

Which, coincidentally, means that to get the same DoF with the 5D as the G1 you would need the same focal length. Which is blindingly obvious - even you have admitted that the DoF is dependent on the lens. And you'd have to crop the 5D image by a factor of 2 to get the same AoV. At which point you're basically using a Micro 4/3 sensor.

Isn't maths beautiful in its symmetry.

Like I said, you're confused.

MichaelMelb_AU
19 May 2013 - 2:02 PM


Quote: .....

Because you should be comparing the 5D/50mm lens against a G1/25mm lens.



I am good enough to accept this and wrote about it myself - OK.


Quote:

Wrong again. To work out the crop you need to square the focal lengths. So you need to crop by 35/25 squared - i.e. 2.



But why that? You contradict yourself and invent the rules on the fly - just to justify your glaring lack of understanding of photographic basics.


Quote:

And you'd have to crop the 5D image by a factor of 2 to get the same AoV. At which point you're basically using a Micro 4/3 sensor.


This is persistent nonsense - 2X crop of full-format sensor does not make Micro 4/3 sensor. For the size of pixels stays the same - i.e. superior to 4/3s . If you understood squares rule properly you would notice by now my earlier omission - crop 2 makes for 4 times lesser number pixels - which is still aplenty (9Mp with D800). But crop 1.4 brings us 2 times less pixels - almost exactly the same as in 4/3s sensor. Yes, maths symmetry is truly beautiful...

And I am getting bored with your illiteracy...

Paul Morgan
Paul Morgan e2 Member 1314810 forum postsPaul Morgan vcard England6 Constructive Critique Points
19 May 2013 - 2:44 PM


Quote: lets say you take a good compact something like canon g and a good ccs like a pen and compare it with results from entry level dslr with kit lens same subject same iso would you notice much difference in a4 print

You lot have gone way of subject.

All I know is, my old 50mm zuiko gives a whole lot more DOF on a film camera than it does on one of my Pens, focused at the same distance Smile

Steppenwolf
19 May 2013 - 5:50 PM


Quote: .....
This is persistent nonsense - 2X crop of full-format sensor does not make Micro 4/3 sensor. For the size of pixels stays the same - i.e. superior to 4/3s .

It's getting a bit difficult replying to your nonsense because you're attempting to obscure the issue. And the size of the pixels has nothing to do with anything - just more obfuscation.

Let's just stick to the fact that a 5D/50mm has half the DoF of a G1/25mm. And they frame the same picture (except for the aspect ratio). Therefore the smaller sensor camera has a larger DoF.

Maybe if you'd actually used a smaller sensor camera you would realise the situation. Taking a photo with an FF camera it's a bit of struggle to get what you want in focus, and using a compact it's a bit difficult to get anything out of focus. I notice it particularly when taking video with a small sensor Panasonic HD camcorder and an APS-C SLT. The camcorder is very easy to use because almost everything is in focus - which works well for video. The SLT has a very shallow DoF and sometimes takes a bit of time to auto-refocus when you move from one subject to another.

Paul Morgan
Paul Morgan e2 Member 1314810 forum postsPaul Morgan vcard England6 Constructive Critique Points
19 May 2013 - 6:53 PM


Quote: Therefore the smaller sensor camera has a larger DoF

With all things being equal it is completely the other way round, ie two 50mm lenses focused at the same distance.

Steppenwolf
20 May 2013 - 8:33 AM


Quote:

With all things being equal it is completely the other way round, ie two 50mm lenses focused at the same distance.

The link below sums it up:

Link

In practice (i.e. for an equivalent field of view) the smaller sensor has the greater DOF.

BTW, where's strawman nowadays? He was usually up for this type of theoretical discussion.

Last Modified By Steppenwolf at 20 May 2013 - 8:34 AM
ChrisV
ChrisV  7718 forum posts United Kingdom26 Constructive Critique Points
20 May 2013 - 11:23 AM

I find it quite astonishing that anyone who has had experience shooting with an SLR [be that film or digital] and a compact digital camera can have failed to notice it's virtually impossible to achieve a defocused background [ie shallow DoF] when shooting at short focal ranges where the subject is out of macro range. That alone is enough to demonstrate the effect of limiting the size of the imaging area.

You get an illustration of what's going on by the fact that fixed lens cameras tend to give 35mm equivalent focal ranges rather than the true physical characteristics of the lens. It's a perfectly logical thing to do because most people are familiar with the idea that you need something less than 35mm equivalent to achieve a fairly wide angle of view and that 200mm is a medium telephoto. The Fuji f550 I have for instance is equivalent to 24-360mm - pretty wide for shooting typically in enclosed spaces on close-ish subjects - people in a small to medium sized room for example - up to quite a long telephoto range.

But in actual fact that lens is actually something like 4mm at the wide end and 66mm at the telephoto end. If you could mount a 'standard' external lens on it [let's say something relatively wide like something starting at 24mm] it would be virtually useless for most day to day shooting.

Mostly the argument that seems to be going on here is whether it's the optic or the sensor that affects DOF. It is of course both, but we talk in short-hand that sensor size is the limiting effect because in practical shooting terms, just like camera manufacturer's do when quoting a lens' zoom range we think in terms of 35mm equivalent because it's the range that matters, not the absolute size of the optic.

It's perfectly well and good to say that a real 75mm lens will get you as shallow [or shallower] DoF on a tiny sensor as one that measures 36mm across, but if you have to be standing 300 metres away from your subject to frame it as you would like there aren't going to be very many situations where that's going to be at all useful unless you are photographing semi-dressed royal spouses or dangerous animals and little else.

Paul Morgan
Paul Morgan e2 Member 1314810 forum postsPaul Morgan vcard England6 Constructive Critique Points
20 May 2013 - 3:24 PM


Quote: I find it quite astonishing that anyone who has had experience shooting with an SLR [be that film or digital] and a compact digital camera can have failed to notice it's virtually impossible to achieve a defocused background [ie shallow DoF] when shooting at short focal ranges where the subject is out of macro range. That alone is enough to demonstrate the effect of limiting the size of the imaging area

Who`s failed to notice ?

MichaelMelb_AU
20 May 2013 - 9:20 PM


Quote: I find it quite astonishing that anyone who has had experience shooting with an SLR [be that film or digital] and a compact digital camera can have failed to notice it's virtually impossible to achieve a defocused background [ie shallow DoF] when shooting at short focal ranges where the subject is out of macro range. That alone is enough to demonstrate the effect of limiting the size of the imaging area....

It's perfectly well and good to say that a real 75mm lens will get you as shallow [or shallower] DoF on a tiny sensor as one that measures 36mm across, but if you have to be standing 300 metres away from your subject to frame it as you would like there aren't going to be very many situations where that's going to be at all useful unless you are photographing semi-dressed royal spouses or dangerous animals and little else.

I would like to remind how the debate went on. First, the question was asked if compacts and 4/3 ( why and?- they are entirely different beasts! ) are the same or better than DSLRs when it comes to small print. Then there were some ridiculous statements that they are actually better than DSLRs (well, that depends in whose hands). Shallow DOF was brought in as one of the flaws (sic!) of DSLRs.
My point still is that DSLR has not shallower, but better controlled DOF - and I showed it on examples that any picture taken with 4/3 can be emulated by a DSLR - by whatever parameter, DOF included. Just needs a bit of thinking and some practical experience. And there are DSLR images that simply impossible to replicate with 4/3 - precisely because their quite rigid (from here to the horizon) DOF - especially with wide optics. Instead I read the arguments based on simplified explanations based on sensor crop effects. That's basics, and it's boring....

Paul Morgan
Paul Morgan e2 Member 1314810 forum postsPaul Morgan vcard England6 Constructive Critique Points
20 May 2013 - 9:46 PM


Quote: Then there were some ridiculous statements that they are actually better than DSLRs

It some respects high end compacts can be better than DSLR`s, it all depends on what you want to do with them and how you use them.

The simple question was pretty much answered on page one, yes I agree all these silly arguments over dof, image circles or whatever is just dull and irrelevant Smile

ChrisV
ChrisV  7718 forum posts United Kingdom26 Constructive Critique Points
20 May 2013 - 11:44 PM


Quote: I find it quite astonishing that anyone who has had experience shooting with an SLR [be that film or digital] and a compact digital camera can have failed to notice it's virtually impossible to achieve a defocused background [ie shallow DoF] when shooting at short focal ranges where the subject is out of macro range. That alone is enough to demonstrate the effect of limiting the size of the imaging area....

It's perfectly well and good to say that a real 75mm lens will get you as shallow [or shallower] DoF on a tiny sensor as one that measures 36mm across, but if you have to be standing 300 metres away from your subject to frame it as you would like there aren't going to be very many situations where that's going to be at all useful unless you are photographing semi-dressed royal spouses or dangerous animals and little else.

I would like to remind how the debate went on. First, the question was asked if compacts and 4/3 ( why and?- they are entirely different beasts! ) are the same or better than DSLRs when it comes to small print. Then there were some ridiculous statements that they are actually better than DSLRs (well, that depends in whose hands). Shallow DOF was brought in as one of the flaws (sic!) of DSLRs.
My point still is that DSLR has not shallower, but better controlled DOF - and I showed it on examples that any picture taken with 4/3 can be emulated by a DSLR - by whatever parameter, DOF included. Just needs a bit of thinking and some practical experience. And there are DSLR images that simply impossible to replicate with 4/3 - precisely because their quite rigid (from here to the horizon) DOF - especially with wide optics. Instead I read the arguments based on simplified explanations based on sensor crop effects. That's basics, and it's boring....

Yes you can replicate what goes on in terms of DoF effect by cropping a larger sensor, but by doing so you're multiplying the angle of view whilst significantly decreasing the resolution. It is possible, but it becomes more difficult the longer the range - I've got a Panasonic 100-300 lens [200-600 eqivalent]. If I were to crop the sensor of my 5DII to m4/3 proportions, I'd be looking at a 5.25 Mp resolution image, not 16mp. The size of lens needed to replicate that field of view in 35mm terms would be back-breaking.

I haven't got access to it now, but I have an image taken with that Fuji I mentioned in a field of corn. The closer stalks, less than a foot away are in sharp focus, as is a local landmark about three miles away and the clouds above. This is at f10 (which I think is the smallest aperture on that camera).

To get anything like that shot from the 5DII (given with less noise, greater dynamic range and colour fidelity) I would have to focus stack. I expect I could get something closer at f32 (although I'm not sure I have a lens capable of closing down so far) and with a wider optic, but then it would be a different shot. It's also going to be able to achieve greater range of focus in macro without as much careful preparation or drastic image cropping.

Don't get me wrong - I'm a great advocate for the benefits a larger sensor area yields, but there are pros and cons with this and the convenience factor of smaller format sensors are not merely limited to weight advantage. If we go to the car analogy again, a Porsche 911 may be generally more desirable than a Mondeo estate, but it's not much cop for taking your garden waste to the tip.

No format is best for everything - and it never has been.

Last Modified By ChrisV at 20 May 2013 - 11:47 PM
strawman
strawman  1021997 forum posts United Kingdom16 Constructive Critique Points
20 May 2013 - 11:56 PM


Quote: BTW, where's strawman nowadays?

Multiple choice time

1 He is in the south of France on a beach sipping cool drinks while a series of nubile young ladies tend to him
2 He discovered latent athletic abilities and has a different life
3 He is working on a Pirelli Calendar
4 He lies at rest waiting for the time when EPZ needs his return
5 He is working on a next generation imaging device for a major player in the market

Last Modified By strawman at 21 May 2013 - 12:00 AM

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