[HarisF1]

Tony Northrup on the other hand is asserting that this is because it it rained less over the top of the 5 gallon bucket.

Perfect response.

The total amount of light hitting a sensor isn't the same as the light intensity per unit area (lux) on the sensor. A fixed aperture doesn't change the light intensity per unit area, so your Sunny 16 rule works equally well with a K1000 as it does with a Pentax Q.

[mikesbike]

I happily use the D FA28-105mm on the K7, and I think anyone would be hard pressed to find any disadvantages to it. Indeed, one big advantage to it is that I won't need to buy another wide to mid-tele zoom if I eventually get a FF Pentax camera, something that figured in my reasoning when I bought the lens.

Quite usable. The only disadvantage is on APS-C you don't get any wide angle, since 28mm comes out as a semi-wide normal. The DA 28-105mm is a fine-performing lens, but I wish Pentax would upgrade their old film-based FA 24-90mm lens which would still provide more useful wide angle on APS-C for those of us who use both that and FF or film.

[UncleVanya]

If you put a 5 gallon bucket in your back yard and right next to it you put a kiddie swimming pool.

When it starts to rain which one will capture more rain? Naturally the kiddie pool will have a larger volume of water in it.

Tony Northrup on the other hand is asserting that this is because it it rained less over the top of the 5 gallon bucket.

And they both will hold the same DEPTH of water if they started empty - the depth is based on the water falling per square inch.

[alamo5000]

And they both will hold the same DEPTH of water if they started empty - the depth is based on the water falling per square inch.

These tests don't measure depth. They measure total volume.

Hence the flaw.

And the resulting 10,000 false teachings on the Internet.

[HarisF1]

The sharpness result is also quite amusing. I wonder what their testing methods were. I'm pretty sure they've produced a video about it but I don't want to waste my time listening to it!

[pschlute]

That video is hogwash

The resolving ability of a lens is the same whether you stick it in front of a FF sensor, an aps-c sensor or a sheet of polaroid film. How he can claim you get less per pixel is beyond me.

The wildlife theory is hogwash too. It has nothing to do with the lens , and everything to do with the pixel pitch of the sensor. Any fool can see that if you use an aps-c camera with a higher pixel pitch than a FF one (eg K-3II versus K-1), the image recorded on the sensor is going to have more resolution on the aps-c sensor (asuming identical pixel to picture processing ability). This would apply whether you use a FF lens, an aps-c lens, or an old jam jar.

Lose depth of field ? Oh lordy, does the man not understand if you use an aps-c camera and the same focal length, you will stand further away from your subject, and it is this that increases DOF.

[stevebrot]

"Total light" is a branch of focal length equivalence theory that failed to gain traction several years ago. In fact, it was pretty much on the downslope of credibility when this video was made in 2014. Tony does a poor job explaining and I suspect that if one were to ask him today about it, he would roll his eyes and change the subject to sports or the weather.

As for FF on crop...I own three crop-sensor lenses and have not noticed any difference in exposure, shadow tonality, etc., though it is pretty difficult to actually test. Even comparing crop to full mode on a K-1, one must change lenses or zoom focal length in order to compare and doing so introduces multiple uncontrolled variables.

FWIW, "total light" is of critical importance to astronomers and telescope enthusiasts.


Steve

[UncleVanya]

These tests don't measure depth. They measure total volume.

Hence the flaw.

And the resulting 10,000 false teachings on the Internet.

You lost me - which "tests"? If you mean exposure - then I disagree that's a depth of sorts. Depth is a proxy for volume per unit of area. The instantaneous depth of a moment of light hitting the sensor is essentially the same metric. The depth per moment of time is akin to the number of lux captured. An f/2.8 lens mounted on any sensor is roughly going to make the same basic exposure at the same ISO.

[ScooterMaxi Jim]

That video is hogwash

The resolving ability of a lens is the same whether you stick it in front of a FF sensor, an aps-c sensor or a sheet of polaroid film. How he can claim you get less per pixel is beyond me.

The wildlife theory is hogwash too. It has nothing to do with the lens , and everything to do with the pixel pitch of the sensor. Any fool can see that if you use an aps-c camera with a higher pixel pitch than a FF one (eg K-3II versus K-1), the image recorded on the sensor is going to have more resolution on the aps-c sensor (asuming identical pixel to picture processing ability). This would apply whether you use a FF lens, an aps-c lens, or an old jam jar.

Lose depth of field ? Oh lordy, does the man not understand if you use an aps-c camera and the same focal length, you will stand further away from your subject, and it is this that reduces DOF.

I'm sure you meant that standing further away "increases" DoF - that is, it becomes less shallow with distance. Otherwise, the point is valid.

What folks tend to forget is that the smaller the sensor the greater the magnification needed. That's where you sense the loss of resolution. Of course, the image circle of a lens has nothing to do with that.

[UncleVanya]

That video is hogwash

The resolving ability of a lens is the same whether you stick it in front of a FF sensor, an aps-c sensor or a sheet of polaroid film. How he can claim you get less per pixel is beyond me.

The wildlife theory is hogwash too. It has nothing to do with the lens , and everything to do with the pixel pitch of the sensor. Any fool can see that if you use an aps-c camera with a higher pixel pitch than a FF one (eg K-3II versus K-1), the image recorded on the sensor is going to have more resolution on the aps-c sensor (asuming identical pixel to picture processing ability). This would apply whether you use a FF lens, an aps-c lens, or an old jam jar.

Lose depth of field ? Oh lordy, does the man not understand if you use an aps-c camera and the same focal length, you will stand further away from your subject, and it is this that reduces DOF.

For years when Film was the only medium it was well known that larger format lenses offered lower resolution than smaller format lenses when adapted to smaller size film. People shooting on the Q platform have been talking about this for a while - the native lenses outperform adapted lenses - however when dealing with crop and full frame the difference is so small that I don't think this is typically seen to be a problem.

What I get frustrated by is that he mixes the equivalence and FF vs. crop lenses together. No matter what you think of equivalence - a FF 200 and a crop 200 at the same f/stop give the same image with respect to these factors on the crop body. So the question isn't related to FF vs. Crop LENS - it's related to the format of the sensor and how you frame things.

[marcusBMG]

Tony Nrotrupp has nice presentational skills but as the preceding posters have said he is well not FoC, just wilfully misleading. The implication of what he says is that lenses are slower on a smaller sensor, this is just plain wrong. The "speed" of a lens ie its widest F-stop (= max light transmittance) , is a physical characteristic of the lens and doesn't change, regardless of what camera you put it on. And it is that that determines exposure. To put alamo5000's rain bucket analogy a different way, the exposure depends on light intensity, not on how big the sensor is/the total number of photons hitting it.
So the photograhic effect you may notice is, as normhead pinpoints, more depth of field on smaller sensor(s).

There is a benefit of using full frame lenses on apsc: you are selecting (effectively cropping) the centre of the image circle projected by the lens, this has the best IQ!

[pschlute]

I'm sure you meant that standing further away "increases" DoF - that is, it becomes less shallow with distance

i did indeed, thanks for pointing out my error, I have corrected it. In my defence i had a cocker spaniel trying to stand on me as I was typing

---------- Post added 11-05-17 at 06:12 PM ----------

For those who have not viewed this, i highly recommend it for a dose of reality.

Come On People, It's Time to Stop Arguing About Crop Factors Already

[alamo5000]

You lost me - which "tests"? If you mean exposure - then I disagree that's a depth of sorts. Depth is a proxy for volume per unit of area. The instantaneous depth of a moment of light hitting the sensor is essentially the same metric. The depth per moment of time is akin to the number of lux captured. An f/2.8 lens mounted on any sensor is roughly going to make the same basic exposure at the same ISO.

There are some tests they do using expensive equipment to test lenses. These lens tests however are flawed. It's on those lens testing protocols that these theories are based.

Given the tests are good for what they are good for but they are also not perfect and result in a lot of wrong ideas.

I'm not an engineer by any means but if I'm not mistaken they replicate a camera with a mount and sensor only that sensor is ultra sensitive and calibrated to measure rather than record light.

Then in a lab test they expose the same type of light of the same intensity across various lenses.

Naturally if you have a lens designed for a crop sensor in an absolute test it won't transmit as much light. This is because it's designed not to do that. The circle of light behind the lens is inherently by design smaller.

If you take scientific tests like that and publish absolute results it's going to show a difference.

[normhead]

i did indeed, thanks for pointing out my error, I have corrected it. In my defence i had a cocker spaniel trying to stand on me as I was typing

I often have a border collie lifting my hand off the keyboard. They are like "come one dude, get off that useless thing and lets go do something important, like go play ball or go for a walk."

---------- Post added 11-05-17 at 01:28 PM ----------

If you take scientific tests like that and publish absolute results it's going to show a difference.

Those test aren't relevant to photography, or we'd all be using old lenses used on 8x10 film cameras, because they transmit more light. We all know better. The reverse is true, we don't use lenses designed for 8x10 film cameras because they usually aren't as sharp, and they would be much heavier than needed. Any nerd can point to irrelevant facts that while true and interesting are not relevant to photographic practice.

The difference between a nerd and genius is that the genius can sift through all those possibly relevant (possibly irrelevant) facts to pinpoint what is relevant to the task at hand. This whole argument is just nerdy. "Look mommy, I know fact, here's what I think it means." The fact is indisputable and available to all, the relevance is understood only by those who understand the subject.

Tony doesn't understand the subject.

He should stick to the empirical, obtaining equipment and telling us what works and how. His theoretical understanding is hogwash.

The main reason for using an FF lens on APS-c.... there's no APS-c version of the lens. If he's saying the best most efficient use of a lens is to use it on the format for which it was designed..... duh.

You need to make a video to explain that?

Well OK then. Lets make some videos for people who can't deduce the obvious. Issues that might confuse people with IQs under 80.

The issue is so uncomplicated if you frame it correctly. The question is , why does Tony make it so complicated? It has to be so uneducate (in photoggraphy) people think he's smart. He certainly doesn't fool any smart people.

[timb64]

Thank goodness we have a resident genius to point us all in the right direction