Lee Jay

Lee Jay

Lives in United States CO, United States
Works as a Electrical Engineer / Wind Energy Research
Joined on Oct 17, 2003

Comments

Total: 457, showing: 41 – 60
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On What is equivalence and why should I care? article (1743 comments in total)
In reply to:

mostlyboringphotog: Lastly, F-stop is useful because it indicates "equivalent" amount of light passing per unit time/area regardless of FL or the aperture diameter. Now by creating another derivative, what does it help?

Does it really help to normalize lens performance or its relative merits?

A lot of posters think so and so may be it's useful but I think it comes at a cost of mudding the definition of "F-stop" and understanding DOF.

Is there not a better way to communicate the difference that a sensor size affects your image making?

Again, thank you all for your patience.

The concept of an f-stop is already very "muddled" in the minds of many people. Just look down at how many people think that f-stop defines the amount of light that passes through the lens and onto the sensor, when it actually controls the light intensity (illuminance) instead.

Direct link | Posted on Jul 8, 2014 at 13:31 UTC
On What is equivalence and why should I care? article (1743 comments in total)
In reply to:

mislav: I don't care

How can the truth be BS?

Direct link | Posted on Jul 8, 2014 at 12:01 UTC
On What is equivalence and why should I care? article (1743 comments in total)
In reply to:

WT21: Incredibly useful concept that sadly leads to some of the most boring and droning discussions on photo forum boards.

Good article that will hopefully clear it up for most.

I discovered (or, rather, rediscovered) equivalence on my own in 2005, and it has guided my purchases and shooting when using multiple formats ever since.

Direct link | Posted on Jul 8, 2014 at 12:01 UTC
On What is equivalence and why should I care? article (1743 comments in total)
In reply to:

Lights: I kinda think products like the Metabones adapters for APS-C and M43 are an interesting side-track in the Equivalence debate.

Why?

Want a short explanation of equivalence?

Crop factor = teleconverter.

Likewise, 1/crop factor = wide converter.

Direct link | Posted on Jul 8, 2014 at 11:56 UTC
On What is equivalence and why should I care? article (1743 comments in total)
In reply to:

hybert46: So finally what is the more compact, potentially cheapest or easiest lens to produce, a FF 100mm f/4 or a m43 50mm f/2? Both should have a roughly similar size of entrance pupil as it is defined by the ratio of focal length over the f-number. Anyone care to elaborate on this, could be interesting!

A lens need not be as long or longer than its focal length. In fact, the definition of a telephoto lens is a lens that's shorter physically than its focal length.

To answer the question, in most cases for equivalent kits, the larger sensor Lena system is smaller and cheaper.

Direct link | Posted on Jul 8, 2014 at 11:51 UTC
On What is equivalence and why should I care? article (1743 comments in total)
In reply to:

WT21: Incredibly useful concept that sadly leads to some of the most boring and droning discussions on photo forum boards.

Good article that will hopefully clear it up for most.

It's common for me to shoot with a 24-105/4 on full frame at ISO 1600 and simultaneously shoot with a 70-200/2.8 on crop (112-320/4.5 equivalent) at ISO 800, for this reason.

Direct link | Posted on Jul 8, 2014 at 02:31 UTC
On What is equivalence and why should I care? article (1743 comments in total)
In reply to:

Lee Jay: "Any two lenses 25mm diameter apertures will give the same depth-of-field of shot at the same shooting distance."

This sentence is still incorrect, Richard.

That works.

Direct link | Posted on Jul 8, 2014 at 02:29 UTC
On What is equivalence and why should I care? article (1743 comments in total)

"Any two lenses 25mm diameter apertures will give the same depth-of-field of shot at the same shooting distance."

This sentence is still incorrect, Richard.

Direct link | Posted on Jul 8, 2014 at 02:04 UTC as 187th comment | 6 replies
On What is equivalence and why should I care? article (1743 comments in total)
In reply to:

gtstone: The title of this article took me back to 1966-1967 when I took workshops with Minor White. One of his big themes was the concept of "equivalence" (or sometimes "equivalents") where he would show us image after image of clouds and try to get us to understand that the image of a cloud-scape was "equivalent" to a feeling he wanted to convey. Similarly sea-scapes and rocks.

Here's a link about this:
http://jnevins.com/whitereading.htm

He never talked about photographic technique: he had lab assistants to help us with that. What he wanted to talk in about in class was how we would respond to a print (as opposed to "react").

Another frequent theme was pre-visualization: you don't look for something interesting to photograph, you look for something that will make an interesting photograph. You look around and pre-visualize what a print of what you see before you would look like considering all the steps to get there. I often wonder what he would have done with with Photoshop!

You're assuming finding something that will make an interesting photograph is the goal. What if the subject is already known and fixed? You find an interesting way to photograph it.

Direct link | Posted on Jul 8, 2014 at 00:23 UTC
On What is equivalence and why should I care? article (1743 comments in total)

The article has correct information. If you think the article is wrong, you should read it and learn rather than helping to perpetuate your own false ideas.

Direct link | Posted on Jul 7, 2014 at 19:44 UTC as 230th comment
On What is equivalence and why should I care? article (1743 comments in total)
In reply to:

photoguy622: Let's not forget the flip side, that a smaller sensor has the benefit of having a great area in focus.

"Stop down a large-sensor system and, so long as the lens will stop down far enough, you can get the same depth-of-field (and you'll get the same diffraction)."

You don't even need the "so long as..." part. This is because all SLR lenses that I know of are capable of putting you way, way out into diffraction-limited territory. Therefore, if you are already stopped down all the way and need even more DOF, you can just shorten the focal length and get even more DOF without the normal loss of resolution you get from cropping the result. This is because the resolution is lost anyway to diffraction. In other words, you weren't pixel-limited, you were diffraction limited.

Direct link | Posted on Jul 7, 2014 at 19:31 UTC
On What is equivalence and why should I care? article (1743 comments in total)
In reply to:

lacikuss: Excellent article...

So why then a Sony RX-100 III is priced at $850? It should cost $450 according to this article...

There is no "depth of field advantage", as it states in the article.

Direct link | Posted on Jul 7, 2014 at 19:25 UTC
On What is equivalence and why should I care? article (1743 comments in total)
In reply to:

Alberto Franco: Hi. in General DPReview is a very good site, and while i think The crop factor is an accurate concept to understand the equivalence of focal lenght. the Fnumber equivalence you are trying to explain is BiG mistake since you are mixing apples and oranges. The Fnumber makes refference to the amount of light a lens allows to pass through NOT the amount of deep of field. So say an F2 lens in MFT is equivalent to an F4 FF lens is like saying that you need F2 in MFT to make the same exposition of F4 on a FF and that is TOTALLY wrong. So, what is equivalent is the DEEP OF FIELD, this way you can certainly say to produce the same deep of field of an F4 on FF you need an F2 on MFT.

F-stop = focal length / aperture

F-stop controls the light per unit of area (illuminance) at the sensor plane.

Aperture (for a given angle of view) controls the total light that is passed through the lens.

Direct link | Posted on Jul 7, 2014 at 19:11 UTC
On What is equivalence and why should I care? article (1743 comments in total)
In reply to:

photoguy622: Let's not forget the flip side, that a smaller sensor has the benefit of having a great area in focus.

Please read the article, as this myth was debunked within.

Direct link | Posted on Jul 7, 2014 at 17:27 UTC
On What is equivalence and why should I care? article (1743 comments in total)
In reply to:

Alberto Franco: Hi. in General DPReview is a very good site, and while i think The crop factor is an accurate concept to understand the equivalence of focal lenght. the Fnumber equivalence you are trying to explain is BiG mistake since you are mixing apples and oranges. The Fnumber makes refference to the amount of light a lens allows to pass through NOT the amount of deep of field. So say an F2 lens in MFT is equivalent to an F4 FF lens is like saying that you need F2 in MFT to make the same exposition of F4 on a FF and that is TOTALLY wrong. So, what is equivalent is the DEEP OF FIELD, this way you can certainly say to produce the same deep of field of an F4 on FF you need an F2 on MFT.

f-stop does not dictate the amount of light a lens allows to pass through, it dictates the light intensity (illuminance). The total light drives the image quality and it goes with f-stop * sensor area, not just f-stop. Thus, for a given field of view, it goes with apparent aperture (not f-stop).

Direct link | Posted on Jul 7, 2014 at 17:19 UTC
On What is equivalence and why should I care? article (1743 comments in total)
In reply to:

mostlyboringphotog: I'm really lost at the value of this article. To whom these things are improtant should know what these numbers mean. To most camera useres, they zoom until they get the frame they want and keep the cam in the auto (intelligent auto, in some cases) and most of the time they get what they are happy with and when not they take another photo or blame the camera. They will not be blaiming, ah, I forgot the equivalence.

There are many uses for this concept for those of us that shoot with multiple formats, especially when shooting them at the same time.

Direct link | Posted on Jul 7, 2014 at 17:18 UTC
On What is equivalence and why should I care? article (1743 comments in total)
In reply to:

chbde: Very good article. It is however slightly incorrect on the topic of diffraction:
"This is because, like depth-of-field, softening from diffraction depends on the actual size of the aperture, not the F-number."

As "Cambridge in Color" (http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm) explains it very nicely, the size of the diffraction pattern on the sensor depends only on the f-number. This is also the reason why diffraction softening is independent of focal length. But one can see the effect of diffraction if the size of the diffraction patterns exceeds the dimensions of a pixel, so it is dependent on pixel density.

"This means diffraction will have the same impact on two images shot at equivalent apertures"

That sentence remains correct, however, for sensors with equal number of pixels.

As a consequence of this, by the way, on a 16MP 2.3" compact the resolution is already diffraction limited at f2.8!

The spot size might depend on the f-stop, but the impact on the final image depends on the aperture. Smaller sensors need more enlargement, thus enlarging the blur circles as well.

Direct link | Posted on Jul 7, 2014 at 17:17 UTC
On What is equivalence and why should I care? article (1743 comments in total)
In reply to:

gstadter: So, if I use cardboard or something, to block light from getting to left 1/2 side of the FF sensor in my D610, the resulting picture taken by the right side of the sensor will, in fact, have more "noise" because the camera had less total light to measure? (and not just 1/2 of an image) I've not tested this yet, but it would be a shock to me if the resulting image(right side of picture) actually became noisy just because I put cardboard over the opposite side of the sensor.

Look at each column of this sample, very carefully (including the labels), and see if it makes clear this discussion:

http://photos.imageevent.com/sipphoto/samplepictures/Constant%20aperture%20comparison%201-6%20crop.jpg

Direct link | Posted on Jul 7, 2014 at 16:04 UTC
On What is equivalence and why should I care? article (1743 comments in total)
In reply to:

Artpt: Thank you DPR for the informative article.

The take home message hear is that maximum depth of field requires the smallest sensor size...clearly cell phones win out here, with their incredibly large depth of field...;)

Nope.

If you move the same lens (same focal length, same f-stop) to a smaller sensor, the DOF would get smaller, not larger, and diffraction would get worse because of greater enlargement (always assume the same final size image).

If you instead change the focal length to keep framing constant but keep f-stop the same, the DOF will get larger, and diffraction will get worse. If you then open up the aperture to make diffraction the same, then DOF will be the same.

In other words, if angle-of-view is the same, then DOF and diffraction go together independent of sensor size.

Direct link | Posted on Jul 7, 2014 at 16:02 UTC
On What is equivalence and why should I care? article (1743 comments in total)
In reply to:

StevenE: Should also talk about the angle at which light strikes the sensor. In FF the angle at the corners is pretty extreme, causing light loss and vignetting. This becomes even more extreme in mirrorless cameras since the flange distance gets smaller, like Sony A7 series.
Smaller sensors may have an advantage in corners, especially in mirroless. I'd be interested in an in-depth analysis of the significance of sensor size, sensor design and flange distance

The angle primarily depends of f-stop.

Direct link | Posted on Jul 7, 2014 at 14:41 UTC
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