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07-16-2015, 01:19 PM   #121
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QuoteOriginally posted by everydaylife Quote
Isn't diststance from camera to subject relevant re DOF?
Of course it is and bringing in telescopes and infinity focus in a discussion about photography applications is completely besides the point.

What the respective poster, who has an entire thread devoted to people discussing his misconceptions at DPReview, appears to be missing is that DOF in photography depends on print size and viewing conditions, in particular degree of enlargement. What may be an acceptable circle of confusion for a small print may be unacceptable for a large print. Different sensor format sizes imply different enlargement factors and hence do affect DOF. The DOF markings on a lens assume certain standard conditions and hence must not be misconstrued as absolute truth. In particular, the DOF markings have to be reinterpreted when the lens is used on a smaller format.

A statement like "f-stop is f-stop" is as helpful as "focal length is focal length". Yes, physical attributes of lenses do not change when used with different formats, but just like the same focal length leads to different FOVs on different formats, the same f-ratio leads to different DOFs.

QuoteOriginally posted by everydaylife Quote
What is more interesting to me is what will I gain if I trade in my k5iis for an FF camera.
We'll only be able to tell once the FF camera has been released. If it has a 36MP sensor, it will offer a 50‰ resolution increase over your K-5 IIs. It will benefit from the lower enlargement factor required for FF etc., but what the real benefits will be can only be known once Pentax has released the camera.


Last edited by Class A; 07-16-2015 at 01:37 PM.
07-16-2015, 01:31 PM - 1 Like   #122
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QuoteOriginally posted by osv Quote
he specifically qualified it as an m4/3 vs. ff scenario.

which apparently went right over your head, lol
That doesn't matter. Focal length is the only thing that affects projected image size (that is, the only thing related to optics; changing distance to subject will of course change the projected image size of the subject). Perhaps you misunderstand what he meant when he said "projected image size." The projected image size is the absolute size of the image when it hits the sensor regardless of the sensor size, so smaller or larger sensors will capture a smaller or larger part of that image, not a smaller or larger version of the image. If the image circle of the lens is smaller or larger it will project a smaller or larger part of the image, not a smaller or larger image.
07-16-2015, 01:46 PM   #123
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QuoteOriginally posted by CFWhitman Quote
That doesn't matter. Focal length is the only thing that affects projected image size.
we are talking about sensor-specific lenses, not putting ff lenses on crop cameras.

focal length will not change the size of the image that's projected on the sensor, in the same manner that putting ff lenses on crop cameras projects a wider image than the sensor is capable of seeing.

---------- Post added 07-16-15 at 01:47 PM ----------

QuoteOriginally posted by Class A Quote
exactly...
07-16-2015, 02:05 PM   #124
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I won't even try to correct you this time. Keep believing the myth. It won't change the truth. There is a reason why the same film emulsion on different format have exactly the same exposure and processing instructions. Size does not matter.

07-16-2015, 02:05 PM - 1 Like   #125
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QuoteOriginally posted by osv Quote
we are talking about sensor-specific lenses, not putting ff lenses on crop cameras.

focal length will not change the size of the image that's projected on the sensor, in the same manner that putting ff lenses on crop cameras projects a wider image than the sensor is capable of seeing.
That's not what the original statement was about. It was about what I said in my previous post. That's why I said that perhaps you misunderstood dtmateojr when he first used the term, "projected image size." I'm guessing that Fogel70 misunderstood as well. Incidentally, just in case there is any question, it doesn't matter what system a lens was made for, at the same focal length, the projected image size will be the same (at least as long as it's mounted at the correct registration distance for the lens of course).
07-16-2015, 02:38 PM - 2 Likes   #126
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Here's another real world example:

There are panoramic cameras that allow you to shoot square images as well. All you have to do is insert a mask that would block out the sides. Guess what, the instructions will not tell you to change your exposure because you now have a smaller "sensor". I wonder why that is ROFL!!!
07-16-2015, 03:33 PM   #127
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QuoteOriginally posted by CFWhitman Quote
Incidentally, just in case there is any question, it doesn't matter what system a lens was made for, at the same focal length, the projected image size will be the same (at least as long as it's mounted at the correct registration distance for the lens of course).
agreed... there is only one meaning for projected image size, but since most everyone out here uses crop cameras, often with ff lenses, they get it confused, and i think that confusion is what fogel and i responded to.

these equivalence threads are loaded with crop people who put ff glass on their cameras, then try to relate as if it was a format-specific lens, which is not equivalence.
07-16-2015, 03:42 PM - 1 Like   #128
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Doesn't matter. Equivalence is flawed.

07-16-2015, 06:00 PM - 1 Like   #129
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QuoteOriginally posted by dtmateojr Quote
There is a reason why the same film emulsion on different format have exactly the same exposure and processing instructions. Size does not matter.
Obviously size does not matter for exposure.

Exposure is a format independent concept as it refers to illumination per unit area.
It makes 100% sense for film emulsions to have format independent instructions. You will however, be familiar with the idea that when using the same emulsion with the same exposure and identical shutter times, the larger format will show less DOF for the same scene (i.e., with a longer lens used on the larger format camera).

You may also be familiar with the experience that trying to enlarge a small (crop) APS-C negative to the same generous output size that is achievable with medium format negatives, will introduce visible noise when both negatives were obtained using the same exposure (because the crop recording was made with less total light).

You will also acknowledge that good DOF calculators require you to specify the format (e.g., APS-C or FF). Why do you think that is, if format size does not play a role?

Contrary to your repeated opinions, the predictions made by optical formulas and equivalence can be measured and verified. In other words, you can actually run an experiment that will confirm the DOF predictions made by a DOF calculator that required the specification of the format size.

You can then jump up and down all day and still claim your opinions are "the truth" but the experiments will confirm optics and equivalence, not your misconceptions.

Last edited by Class A; 07-16-2015 at 06:13 PM.
07-16-2015, 06:03 PM - 1 Like   #130
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I think Class A wrote something I'm in complete agreement with. Someone check and see if hell just froze over.
07-16-2015, 06:24 PM   #131
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QuoteOriginally posted by normhead Quote
I think Class A wrote something I'm in complete agreement with. Someone check and see if hell just froze over.
I don't know about the entire dominion, but it's frozen where I am
07-16-2015, 07:39 PM   #132
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QuoteOriginally posted by Class A Quote
Obviously size does not matter for exposure.

Exposure is a format independent concept as it refers to illumination per unit area.
It makes 100% sense for film emulsions to have format independent instructions. You will however, be familiar with the idea that when using the same emulsion with the same exposure and identical shutter times, the larger format will show less DOF for the same scene (i.e., with a longer lens used on the larger format camera).

You may also be familiar with the experience that trying to enlarge a small (crop) APS-C negative to the same generous output size that is achievable with medium format negatives, will introduce visible noise when both negatives were obtained using the same exposure (because the crop recording was made with less total light).

You will also acknowledge that good DOF calculators require you to specify the format (e.g., APS-C or FF). Why do you think that is, if format size does not play a role?

Contrary to your repeated opinions, the predictions made by optical formulas and equivalence can be measured and verified. In other words, you can actually run an experiment that will confirm the DOF predictions made by a DOF calculator that required the specification of the format size.

You can then jump up and down all day and still claim your opinions are "the truth" but the experiments will confirm optics and equivalence, not your misconceptions.

DoF is not the problem with equivalence. The problem is exposure. Equivalence INSISTS that f/5.6 is equivalent to f/11 because you can bump the ISO on f/11.

And that's the ROFL part of that broken "theory".
07-16-2015, 08:16 PM   #133
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QuoteOriginally posted by Class A Quote
Obviously size does not matter for exposure.

Exposure is a format independent concept as it refers to illumination per unit area.
It makes 100% sense for film emulsions to have format independent instructions. You will however, be familiar with the idea that when using the same emulsion with the same exposure and identical shutter times, the larger format will show less DOF for the same scene (i.e., with a longer lens used on the larger format camera).

You may also be familiar with the experience that trying to enlarge a small (crop) APS-C negative to the same generous output size that is achievable with medium format negatives, will introduce visible noise when both negatives were obtained using the same exposure (because the crop recording was made with less total light).

You will also acknowledge that good DOF calculators require you to specify the format (e.g., APS-C or FF). Why do you think that is, if format size does not play a role?

Contrary to your repeated opinions, the predictions made by optical formulas and equivalence can be measured and verified. In other words, you can actually run an experiment that will confirm the DOF predictions made by a DOF calculator that required the specification of the format size.

You can then jump up and down all day and still claim your opinions are "the truth" but the experiments will confirm optics and equivalence, not your misconceptions.
Dtmateojr got owned.

---------- Post added 2015-07-16 at 23:26 ----------

QuoteOriginally posted by dtmateojr Quote
Here's another real world example:

There are panoramic cameras that allow you to shoot square images as well. All you have to do is insert a mask that would block out the sides. Guess what, the instructions will not tell you to change your exposure because you now have a smaller "sensor". I wonder why that is ROFL!!!
You don't need to change exposure. But enlarge that crop to the size of the original and you'll notice more grain (noise).

QuoteOriginally posted by dtmateojr Quote
Doesn't matter. Equivalence is flawed.
This is your problem. You are so invested in your opinion that you won't actually think about counter-arguments.

QuoteOriginally posted by dtmateojr Quote
DoF is not the problem with equivalence. The problem is exposure. Equivalence INSISTS that f/5.6 is equivalent to f/11 because you can bump the ISO on f/11.

And that's the ROFL part of that broken "theory".
50mm F5.6 ISO 200 on m4/3 has the same DOF, same FOV, same noise, same diffraction, same perspective (at the same subject distance), as 100mm and f11 ISO 800 on FF, as long as the sensors are similar design and generation. This is easily verifiable at DXOMark.

Last edited by audiobomber; 07-16-2015 at 08:52 PM.
07-16-2015, 08:40 PM   #134
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QuoteOriginally posted by dtmateojr Quote
DoF is not the problem with equivalence. The problem is exposure. Equivalence INSISTS that f/5.6 is equivalent to f/11 because you can bump the ISO on f/11.

And that's the ROFL part of that broken "theory".
OK, please explain it to me like I'm a six year old, because I am, not for the first time, failing to understand.

I can shoot my 50mm lens on my APS-C body at f5.6 and obtain a specific image. I can also obtain, from the same shooting position, the same image (i.e. same exposure, FOV, and DOF) using a 75mm lens on my FF at f8. As it happens, my APS-C was set to ISO 100, which resulted in a shutter speed of 1/125th sec. My FF was also set to ISO 100, which resulted in a shutter speed of 1/60th sec. And that is that.

I now want to repeat the above, but the scene is darker, which results in my APS-C indicating a shutter speed of 1/30th, even after bumping ISO to1600. The the FF body now indicates a speed of 1/15th sec, also at ISO 1600. Under the circumstances, I am not sufficiently confident that this 1/15th SS is appropriate, and I wish for a minimum of 1/30th. I therefore bump my FF ISO to 3200, which magically results in the FF meter indicating a shutter speed of 1/30th, and I am where I want to be.

Now, if I were to view both of the above (second shoot) images at the same size, I understand DXO to be telling me that since the sensor tech level of my APS-C and FF is the same, I should pretty well end up with the same noise level. I believe there have been numerous posts demonstrating the lower noise level of FF using DXO methodology. But I understand you to be saying that such is not the case.

So where am I going wrong?
07-16-2015, 09:34 PM   #135
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QuoteOriginally posted by BrianR Quote
Where do you think the light that's following this different path came from? It's exactly the extra light that was hitting the aperture blades before, but is no longer blocked since you've opened the aperture. This additional light is enlarging the blur discs.
Oh, come on, Brian!

This is another example of confusing correlation with causation.

Opening up the aperture let in more light, but opening up the aperture also made the cone of light (however dark or bright) falling on the sensor broader.

It was the aperture that was the key.
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