[BrianR]

But AGAIN, that has NO relevance to the initial post.

Is this really your only complaint here? That the discussion has wandered outside the scope of the OP?

And you're taking the approach of assuming we're all a bunch of idiots who don't realize this?

[amoringello]

Is this really your only complaint here? That the discussion has wandered outside the scope of the OP?

And you're taking the approach of assuming we're all a bunch of idiots who don't realize this?

Um, duh! Of course it is the only complaint. It has been with almost every single post I've made.
If that isn't blazingly apparent, I'm not sure what else to say but to agree with your second line.

Until the basic concept is understood, all these arguments talking about cropping and enlarging have absolutely no bearing or relevance.
The complete ignorance of that fact has been unbelievable.
I do believe that many of the comments here are by those who fail to have that most basic understanding of the initial post.
So although I hate to infer people are stupid, they are certainly ignorant of basic concepts.

[BrianR]

Um, duh! Of course it is the only complaint. It has been with almost every single post I've made.
If that isn't blazingly apparent,...

It wasn't, eg. your posts #18 and especially 70 (where it was quite clear what assumptions were being made, and that they were not directly answering the OP's question), but I'll take your word for it.

Anyway, I'm pretty done here since I don't agree with what topics you're declaring to be relevant or not and I'm tired of seeing people get yelled at.

[slip]

As the OP I have to say that it is a shame we can't have a good conversation with everyone's point of view respected

Randy

[amoringello]

Anyway, I'm pretty done here since I don't agree with what topics you're declaring to be relevant or not ...

Read the first post. I'm not sure where the disagreement comes in.

---------- Post added 03-16-16 at 09:46 PM ----------

As the OP I have to say that it is a shame we can't have a good conversation with everyone's point of view respected

Randy

Point of view is one thing, but it is something altogether different when inaccurate answers are given as fact with no relevance to the question and in context are completely wrong.

[derekkite]

Essentially on either a FF sensor and apsc sensor with the same pixel density or the same sensor cropped vs whole frame you lose resolution as you magnify. If you look at any of the photos at 100% on your computer screen, pixel to pixel, they would be identical.

If you provide a print of the image of the same size from a crop and full, the transition from focus to not focus near and beyond the focal point would have a different characteristic and the point of apparent out of focus would be closer to the focal point on an apsc crop. Or a narrower depth of field.

If you take the same image framed the same way, for example head and shoulder shot with both formats, then what? Say with the same lens, 77mm. Not realistic, you would select a different one because it is cheaper to buy a different lens than to renovate your studio. But for the sake of argument. The distance to subject would be different.

OK, numbers. I did up a spreadsheet to calculate dof for when I was shooting bats last summer. My strategy was to dof stack with three bodies creating an in focus cube about a meter cubed. The dof charts didn't allow easy playing with the numbers, and I found the assumptions of the charts didn't proved a sharp enough box.

So these are very sharp dof numbers, probably awful for portraiture. The circle of confusion is set very small.

70mm lens. The fov is based on the Sigma 70mm macro, FF capable and a very nice sharp lens. As well as A50 1.4.

Distance 2m
FF 450*673 fov, 63.52 dof.
Apsc 440*675, 41.48 dof.

1m
FF 225*337 15.3 dof
Apsc 224*337.5 10 dof 1005mm distance

1m distance
50mm f2.8
FF 30.5 dof
Apsc 20.

All mm.

So the dof is narrower on apsc. I have read in many places that dof is narrower and more of an issue on FF. Is the transition more dramatic? Or are we seeing the effects of more than one factor, ie resolution and dof?

[2351HD]

As the OP I have to say that it is a shame we can't have a good conversation with everyone's point of view respected

Randy

Randy, it's really simple. It goes like this.

If you shoot an image with a 16mp crop sensor and 50mm lens at 5m, you will get the same image if you use a 36mp FF sensor in crop mode, with a 50mm lens at 5m. They are one in the same.

If you shoot the FF at 36mp, then when you get home you crop it in PS down to 16mp, it will be the same as the crop sensor photo, absolutely identical.

Choose your poison, either is fine and it comes down to which sensor has the best tech, lowest noise and highest DR or whatever it is that you are looking for.

[amoringello]

So the dof is narrower on apsc. I have read in many places that dof is narrower and more of an issue on FF. Is the transition more dramatic? Or are we seeing the effects of more than one factor, ie resolution and dof?

First comment I have is that it is a bit strange that you are seeing narrower DOF from the APSC sensor. Like you mention, things should be quite the opposite. The Holy Grail for many is to buy a FF to more easily achieve a shallower DOF. It would be interesting to know more about how you obtained your measurements.

Regardless...
Most DOF calculations assume you're using the full size of the sensor and comparing them side by side in equivalent sizes. (meaning modifying one to look the same size as the other -- again if you modify a value, other values must also change!)
And it sounds like you have a pretty good understanding of that.

The problem is that we are not talking about comparing edge to edge FF against a smaller crop area.
Get past that misconception and you'll be in a perfect position to understand the issue from the original post. *This is where so many people are failing.*


We're talking about how the light looks within a specific region. Using only the area of the cropped sensor, will result in an identical image. (minus any difference in technology, which is why the K-1 is a perfect example for real comparison)

Imagine a flashlight shining on a wall.
Cut out a portion the wall the size of an 8"x10".

Go to another wall doesn't matter what size, and create an identical sized circle from your flashlight.
Again cut out an 8"x10" portion.

The light within that area does not change. It cannot change. Simple physics (and trivial logic) guarantees that.
The size of the wall does not affect what the flashlight does within that 8x10 area... how could it?

Think of the light coming from the lens. Same lens. Same focal length. Same distance to subject. Same Aperture.
That light creates a consistent circle of light behind it, much like the flashlight on a wall.

The size of the surface behind the lens does not and can not change the light coming from the lens.
Simple physics (and trivial logic) guarantees that.


A FF sensor is not some magical device that bends the laws of physics and creates better images from thin air.
It is really that simple and basic.

There is not a lot of room for mis-understanding.
I really don't know where this recent engineered "anger" would come from. :-(

[audiobomber]

I don't see the point of arguing DOF. Everything you need to know is readily available here:
A Flexible Depth of Field Calculator

[amoringello]

I don't see the point of arguing DOF. Everything you need to know is readily available here:
A Flexible Depth of Field Calculator

The argument isn't (or should not) be with DOF.
The problem that those charts are not directly relevant if one does not understand how it is calculated or rather what it really means in real life and mainly, to the point, with relevance to the original question of this thread.

Now, I could be wrong. It has been known to happen. :-)
I'll accept that if someone can show where I am wrong without bringing in some form of FF mysticism or magic into the equations.

So far, I believe that no one who understands the basis on which the original post is made, and understands simple behavior of light, has really been in disagreement. It's only a few who fail to comprehend the parameters surrounding the initial question or have a zealot-like love for FF and must defend its superiority in any way possible. (I don't get it, its a tool. With its pluses and minuses. Its not something to fetishize)

[derekkite]

First comment I have is that it is a bit strange that you are seeing narrower DOF from the APSC sensor. Like you mention, things should be quite the opposite. The Holy Grail for many is to buy a FF to more easily achieve a shallower DOF. It would be interesting to know more about how you obtained your measurements.

Regardless...
Most DOF calculations assume you're using the full size of the sensor and comparing them side by side in equivalent sizes. (meaning modifying one to look the same size as the other -- again if you modify a value, other values must also change!)
And it sounds like you have a pretty good understanding of that.

The problem is that we are not talking about comparing edge to edge FF against a smaller crop area.
Get past that misconception and you'll be in a perfect position to understand the issue from the original post. *This is where so many people are failing.*


We're talking about how the light looks within a specific region. Using only the area of the cropped sensor, will result in an identical image. (minus any difference in technology, which is why the K-1 is a perfect example for real comparison)

Imagine a flashlight shining on a wall.
Cut out a portion the wall the size of an 8"x10".

Go to another wall doesn't matter what size, and create an identical sized circle from your flashlight.
Again cut out an 8"x10" portion.

The light within that area does not change. It cannot change. Simple physics (and trivial logic) guarantees that.
The size of the wall does not affect what the flashlight does within that 8x10 area... how could it?

Think of the light coming from the lens. Same lens. Same focal length. Same distance to subject. Same Aperture.
That light creates a consistent circle of light behind it, much like the flashlight on a wall.

The size of the surface behind the lens does not and can not change the light coming from the lens.
Simple physics (and trivial logic) guarantees that.


A FF sensor is not some magical device that bends the laws of physics and creates better images from thin air.
It is really that simple and basic.

There is not a lot of room for mis-understanding.
I really don't know where this recent engineered "anger" would come from. :-(

Go do a dof calculation on any of the dof calculators available. Do it on more than one. That is the result you will get.

So all the stuff saying that you need to shoot stopped down more to get the same things in focus on FF is wrong. In fact it is the opposite.

I want to be corrected if I'm wrong. What I'm seeing is that you don't give up the Iso and dr advantages of the FF sensor to get an equivalent focus depth.

---------- Post added 03-17-16 at 05:41 AM ----------

I challenge everyone here to go do a dof calculation.

Now I want to know, because I don't, why the impression of people shooting with full frame that the dof is either narrower or more of an issue. Same with medium format.

[beholder3]

So all the stuff saying that you need to shoot stopped down more to get the same things in focus on FF is wrong. In fact it is the opposite.

I want to be corrected if I'm wrong. What I'm seeing is that you don't give up the Iso and dr advantages of the FF sensor to get an equivalent focus depth.

This is an example of where the issues begin: Much too short generic statements with lots of parameters not given.
The whole topics here only can be discussed if everyone names a lot of parameters.
Example:

1. Same framing = different focal length (=different lens or zoom) + different subject distance and same FoV, same aperture number --> FF has less DoF than APSC
2. Same framing = different focal length + different subject distance and same FoV, equivalent aperture number --> both have the same DoF
3. Same lens, same aperture, same subject distance, different framing --> FF has more DoF than APSC (this is what you would emulate by post cropping)

So yes, if you want same FoV and framing you need a different lens and this would need to be stopped down on FF to achieve the same larger DoF (item #2 above).

---------- Post added 17th Mar 2016 at 13:48 ----------

Wouldn't the chroma (colour) noise be better on the K1 just because it's a better sensor all other things being equal?

Nobody will know until we can see a sample and compare. This is not answerable from theory, just from practical experience.

[BrianR]

Statements like "FF has less DoF than Aps-c" are utterly meaningless without knowing the relevant parameters. Not bothering to lay out or think about these parameters is what's caused countless arguments on these forums.

This is an example of where the issues begin: Much too short generic statements with lots of parameters not given.
The whole topics here only can be discussed if everyone names a lot of parameters.

This quote is worth repeating several times, but I'll just do it once

[amoringello]

Go do a dof calculation on any of the dof calculators available. Do it on more than one. That is the result you will get.

So all the stuff saying that you need to shoot stopped down more to get the same things in focus on FF is wrong. In fact it is the opposite.

I want to be corrected if I'm wrong. What I'm seeing is that you don't give up the Iso and dr advantages of the FF sensor to get an equivalent focus depth.

---------- Post added 03-17-16 at 05:41 AM ----------

I challenge everyone here to go do a dof calculation.

Now I want to know, because I don't, why the impression of people shooting with full frame that the dof is either narrower or more of an issue. Same with medium format.

This is drifting form the original question, but DOF (Depth of Field) is a perception. Its calculation based on relatively common visual agreement. But true focus is a plane. There is no depth of focus in front of the lens.

DOF calculations are self consistent and can be used to roughly judge expectations, but they are not a law.

DOF will change if you enlarge or decrease the viewing size. It will even vary with an individual's eyesight. And is probably why people are getting so confused by FF vs Crop. They are failing to realize the FF sensor will capture a larger area of view than a crop sensor (with all else being equal). and that is affecting the calculations.

As the area of view gets larger (NOT focal length), the static elements in the view appear to become smaller. Thus DOF takes up less percentage of the sensor realestate an appears smaller.
Reverse with crop. As the area of view gets smaller, static elements in the view appears to take up more of the visible realestate and they, along with DOF, appear larger.

So if you take a photo with FF, it may print x 8x10. If you take the same photo (NO changes to focal length, aperture nor distance to subject) you may end up with a 5x7 (I'm too lazy to do the math for exact sizes, but you get the idea)

Put them on top of each other and the small print will fit perfectly and indistinguishably on top of the larger one.
BUT, blow up that small image to be the same size as the larger one, and suddenly things look larger. It looks as if you were in closer to the subject. You will see more noise, as it has also been enlarged. DOF will appear larger since the relative area that is in focus has also been enlarged.

It all comes down to the image circle coming from the lens.
Keep in mind what has to be done in the real world to the light and this stuff pretty much explains itself.
The size of the sensor cannot possibly affect the light coming from the lens. (again if physics allowed for that, the universe would probably have dissolved itself in an instant)



With that, on a crop sensor you have to open your aperture to give the same perception of DOF that would be seen on a given percentage of the surface area of a FF sensor. If you stop down on a FF you can get similar DOF as what is perceived from the smaller crop surface area.

** Again though, if you're comparing the same area (crop sensor vs. crop area within a larger sensor) no compensation needs to be done.
otherwise you're dealing with different variables, and this is not relevant to question in the initial post.



I am going to find it so sad when someone buys K1 and shoots using the Crop mode, yet expects that they will get better DOF merely because the sensor itself is larger.... ("but, but, but, the DOF chart says I get better images with a FF sensor and everyone says cropping out the middle does not affect that...") I find it disturbing that this false information is propagated with such zealousness without understanding simple principles.

[derekkite]

OK guys, I posted a scenario.With calculations and results. There are lots, calculating the field of view by looking up the specs on the specific lens, calculating the distance from subject. Then the dof, etc.

This is why I am asking. No arguing, I really get the stuff on circle of confusion, etc. I was told to ignore the pixel to pixel stuff, I'm sorry but that is where I shoot. I know where I'm losing. I did that spreadsheet to figure out around severe and hard technical limitations.

But I also trust people's intuition or experience. People are describing something, and I want to know what it is. It comes down to physics. In my work if I find an anomaly I don't question Charles or Faraday, I look for other factors causing what I am seeing.