Erik Magnuson

Erik Magnuson

Lives in United States Cape Canaveral, FL, United States
Has a website at http://www.pbase.com/maderik
Joined on Dec 29, 2000
About me:

This is what I'd like to appear on my public 'posters (sic)
profile.'

Comments

Total: 254, showing: 41 – 60
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On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

LaFonte: But why do I even have to care about equivalent or not exposure?
If I say to two guys don't use your camera metering, pull out my old light meter and tell to two guys with very different camera: set your ISO 100, set 1/60, and aperture 2.2 and you will be fine, they would both get properly exposed picture. Right? Even that one geezer have 7d and the other have e-pm.
As I understand, that is the whole point of having equivalent exposure that translates to everybody. So we understand each other without looking what size of sensor you have. Starting recalculating what aperture means in different sensor sizes is good only and only for assuming DOF not for exposure.
So maybe call it equivalent DOF.
Or is it that I totally don't get it?

@mostlyboringphotog Most would know the answer but usually don't think of it in terms "equivalence". Instead they would think "I don't want to go over ISO 1600, so I'll use 1/500 and whatever aperture I need for that." Equivalent DOF is not important to most photographers unless they are unable to match really shallow DOF.

Direct link | Posted on Jul 9, 2014 at 21:15 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

LaFonte: But why do I even have to care about equivalent or not exposure?
If I say to two guys don't use your camera metering, pull out my old light meter and tell to two guys with very different camera: set your ISO 100, set 1/60, and aperture 2.2 and you will be fine, they would both get properly exposed picture. Right? Even that one geezer have 7d and the other have e-pm.
As I understand, that is the whole point of having equivalent exposure that translates to everybody. So we understand each other without looking what size of sensor you have. Starting recalculating what aperture means in different sensor sizes is good only and only for assuming DOF not for exposure.
So maybe call it equivalent DOF.
Or is it that I totally don't get it?

To pile it on -- let's say we are shooting birds late in the day: I have an FF camera with a 600mm f/5.6 lens and you have an MFT camera with a 300mm f/2.8 lens. You ask me what I'm shooting at. If I say I'm getting good exposures at 1/500, f/5.6, ISO 6400 would you want to set your MFT camera to those same numbers? No. But if you set your camera to the "equivalent" of 1/500, f/2.8 and ISO 1600 you would get similar brightness, DOF, and noise.

Direct link | Posted on Jul 9, 2014 at 21:04 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

shii: I followed the discussion with great interest but failed to grasp the concept of "total light." In the article it says " ... (while the intensity is the same) because the more (total) light you capture, the less noisy your image, ...". Noise is determined at the pixel level and each pixel does not know how much total light the sensor is capturing. So why would the total light affect noise? Take a Nikon D800, for example. Shoot in FF and then in crop mode. Are we saying the crop mode will have more noise though it is basically the same camera? Comparisons only make sense while we are taking the same picture. The cropped photo will have higher noise only if we move the camera away to keep the same frame but still use the same aperture. But then the DOF will not be the same so it is not the same comparison. So, once again, why does total light matter? Is that to avoid the discussion of having to keep the same frame between FF and cropped?

The problem with just using a crop is that you are also changing the number of area samples. Equivalence is about *the same size print*. Certainly for the same size print, any single noisy pixel will be larger and more visible in the final image with the crop.

Direct link | Posted on Jul 9, 2014 at 20:52 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

LaFonte: But why do I even have to care about equivalent or not exposure?
If I say to two guys don't use your camera metering, pull out my old light meter and tell to two guys with very different camera: set your ISO 100, set 1/60, and aperture 2.2 and you will be fine, they would both get properly exposed picture. Right? Even that one geezer have 7d and the other have e-pm.
As I understand, that is the whole point of having equivalent exposure that translates to everybody. So we understand each other without looking what size of sensor you have. Starting recalculating what aperture means in different sensor sizes is good only and only for assuming DOF not for exposure.
So maybe call it equivalent DOF.
Or is it that I totally don't get it?

If those two have the cameras set to the same ISO, then the same f-stop and shutter speed will give the similar brightness. But it will give different DOF and noise levels (for the same size print.) Or they could shoot with the same shutter speed and different ISO & aperture to get similar noise and DOF. What's more important to the viewer of a photo: the numeric ISO and f-stop used (which may not even be available) or actual image qualities like noise and DOF?

Direct link | Posted on Jul 9, 2014 at 20:28 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

mislav: I don't care

@mislav Depending on the crop, an 8x10 is an 7-8x enlargement for 35mm. You are saying the grain will be 8x larger when pushed? I think grain would be less but DR might suffer because film is notably less linear than digital. Since the correct factor for 8x10 vs. 35mm is closer to 6 stops, what if you shot Tech Pan in 35mm and I shot 8x10 HP5+ pushed one stop. (BTW, have you ever seen an 8x10 contact print?)

Or to bring this closer to current cameras, you shoot Tech Pan in 110 format (i.e. MFT) and I'll shoot Plus-X in 35mm. How much difference will there be?

Direct link | Posted on Jul 8, 2014 at 14:51 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

mostlyboringphotog: I guess now I understand why "equivalence" becomes such a heated topic while it's nothing more than manipulating some math values.

Is 2+2 equivalent to 3+1?

What I object to the F-stop equivalence is that I think it buries the understanding of DOF even deeper while creating that DOF is sensor size dependent misconception.

For example, if you crop an image from a FF to a size of crop image, do you now need to crank up to the equivalent exposure using PP to maintain the DOF? Does DOF change if an image is cropped?

DOF is a function of FL, F-stop (EP) AND distance to the subject.
You don't need "equivalent F-stop" if you move closer to the subject with a crop camera to maintain the same DOF of FF.
If you don't want to move, you may change the FL (not equivalent).
And if your lens is not a constant F-stop zoom (or prime), then you can change the F-stop to a DOF calculated F-stop (not equivalent), then adjust ISO or shutter speed or add ND-filter to maintain the same exposure.

It's too late: did you know there is a "FocalLengthin35mmFormat" tag in EXIF? However, *you* never have to state equivalence if you don't wish to.

Direct link | Posted on Jul 8, 2014 at 14:29 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

Jack Hogan: A good start and a good write up.

I would add a section on equivalent spatial resolution. Also, was the GH4 free? Your shareholder says that today the Panasonic/Leica 42.5/1.2 costs $1599 by itself.

Because the bodies were chosen for closest matching pixel count and not price or features.

Direct link | Posted on Jul 8, 2014 at 14:22 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

mostlyboringphotog: I guess now I understand why "equivalence" becomes such a heated topic while it's nothing more than manipulating some math values.

Is 2+2 equivalent to 3+1?

What I object to the F-stop equivalence is that I think it buries the understanding of DOF even deeper while creating that DOF is sensor size dependent misconception.

For example, if you crop an image from a FF to a size of crop image, do you now need to crank up to the equivalent exposure using PP to maintain the DOF? Does DOF change if an image is cropped?

DOF is a function of FL, F-stop (EP) AND distance to the subject.
You don't need "equivalent F-stop" if you move closer to the subject with a crop camera to maintain the same DOF of FF.
If you don't want to move, you may change the FL (not equivalent).
And if your lens is not a constant F-stop zoom (or prime), then you can change the F-stop to a DOF calculated F-stop (not equivalent), then adjust ISO or shutter speed or add ND-filter to maintain the same exposure.

What do you mean "now"? Compact digital cameras have been marketed with "35mm equiv" focal lengths since forever. It's only the acknowledgement that f-stop also has equivalence and it's misleading to give one with out the other (i.e. changing one 'f' without changing the other) that is new.

Direct link | Posted on Jul 8, 2014 at 14:14 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

mislav: I don't care

> If you remember film days, you wouldn't get finer grain if you shot HP5+ on 8x10" vs 35 mm.

Ok, let's try this. I'll shoot 8x10" HP5 and you shoot 35mm HP5. We'll both then make an 8x10" print. Which will have finer grain? The key concept you missed is that the comparisons are only valid for *the same size print*. This should be obvious because DOF is defined to print size vs. viewing distance.

Direct link | Posted on Jul 8, 2014 at 13:44 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

mostlyboringphotog: I guess now I understand why "equivalence" becomes such a heated topic while it's nothing more than manipulating some math values.

Is 2+2 equivalent to 3+1?

What I object to the F-stop equivalence is that I think it buries the understanding of DOF even deeper while creating that DOF is sensor size dependent misconception.

For example, if you crop an image from a FF to a size of crop image, do you now need to crank up to the equivalent exposure using PP to maintain the DOF? Does DOF change if an image is cropped?

DOF is a function of FL, F-stop (EP) AND distance to the subject.
You don't need "equivalent F-stop" if you move closer to the subject with a crop camera to maintain the same DOF of FF.
If you don't want to move, you may change the FL (not equivalent).
And if your lens is not a constant F-stop zoom (or prime), then you can change the F-stop to a DOF calculated F-stop (not equivalent), then adjust ISO or shutter speed or add ND-filter to maintain the same exposure.

The point is that both systems (FF+85mm f/1.8 and APS-C+56mm f/1.2) will produce "equivalent" images when shot wide open from the same location and same lighting with the same shutter speed (but with ISO adjusted for correct brightness.) This may be important to you if you are deciding between systems or want to be able to replicate a style of photo with a different system than the original.

Direct link | Posted on Jul 8, 2014 at 13:38 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

fmian: What is the 4/3 equivalent in 110 format?

110 image area is 13x17mm. 4/3 is 13x17.3. So they are already equivalent.

Direct link | Posted on Jul 8, 2014 at 03:45 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

forpetessake: Will this article finally stop those f2=f2=f2 stupid arguments? I doubt it. Stupid arguments come from stupid people: those same people who were explained the equivalence to many times before without any success.

There may be 30+ different combinations of aperture, shutter speed, and ISO that give the same brightness or effective exposure. Shutter speed is essentially the same between most cameras, but aperture and ISO can have very different impacts to the final image with different sensor sizes. You can't consider one without the other.

Direct link | Posted on Jul 7, 2014 at 21:39 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

JanMatthys: DPreview completely missed the point and fell for the marketing crap.

If you want to know the "equivalent" all you have to do is take a FF image and CROP IT by either x1.5 x2 or x2.7.

A 36mp sensor like the Nikon D800 will provide a decent 6mp image at the highest crop factor of x2.7 which is fine for a prints up to 8 x 10

If you need higher resolution at x2.7 and you find yourself cropping your images up to x2.7 very often then you should buy a 1" sensor camera, otherwise a FF sensor and good glass is really your most versatile option

@joe6pack: there is little demand for high quality 24mm lenses that shoot at f/33.6 equiv. You could always try pinhole photography if that's the style of image you prefer (22mm @ f/128 for an ideal pinhole)

Direct link | Posted on Jul 7, 2014 at 20:53 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

forpetessake: Will this article finally stop those f2=f2=f2 stupid arguments? I doubt it. Stupid arguments come from stupid people: those same people who were explained the equivalence to many times before without any success.

One of the settings on all of my meters is ASA/DIN or ISO. (OK, I have one old "weston units" meter but still...) Why do you pick any given ISO?

Direct link | Posted on Jul 7, 2014 at 20:30 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

forpetessake: Will this article finally stop those f2=f2=f2 stupid arguments? I doubt it. Stupid arguments come from stupid people: those same people who were explained the equivalence to many times before without any success.

@NowHearThis: so there is no other way to increase the shutter speed than to increase the aperture to f/2? IMHO, the problem is that some people forget WHY they choose a certain ISO setting other than habit.

Direct link | Posted on Jul 7, 2014 at 19:31 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

forpetessake: Will this article finally stop those f2=f2=f2 stupid arguments? I doubt it. Stupid arguments come from stupid people: those same people who were explained the equivalence to many times before without any success.

If brightness is the only important attribute, a camera phone with an f/2 lens and ISO 100 also produces the same brightness. And all three at ISO6400 and f/2 are also the same brightness.

Direct link | Posted on Jul 7, 2014 at 19:11 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

Happy Jones: In the article is shows an APS sensor does not use the full aperture of a FF lens. Since f-stop is focal length divided by lens diameter and has no relationship to sensor size, this is confusing. Couldn't an APS lens be made with a much smaller diameter since much of it is not being used and still have the same light gathering? Are we saying an APS F1.8 lens projects more light on to an APS sensor since f-stop does not change with sensor size? An APS lens will vignette on a FF sensor because it concentrates light more to the center than a FF lens.
Say for a 50mm lens couldn't a lens direct all the light of a 28mm opening towards an APS size sensor rather than spreading it out over a FF size sensor? We would see vignetting on the FF sensor with the lens because the light is more focused. To me then this F/1.8 lens would put the same amount of light on the APS sensor (but more concentrated to a smaller area) as a FF lens would on a FF sensor.

*This* article compares lenses designed for each format (Canon 85mm F1.2, Fujifilm 56mm F1.2, Panasonic 42.5mm F1.2 OIS, Nikon 1 32mm F1.2). Depending on the design goals an APS-C lens can be made smaller (i.e. Canon 22mm f/2 EF-M).

If you change the cone of light optically as you suggest, it's called a focal-reducer (one such product is called "SpeedBooster".) But it actually changes the optical properties such that the combination is no longer "50mm" focal length or the same f-stop ('cause the "f" has changed). Just like adding a 2x teleconverter to a 200mm lens make it 400mm optically.

Direct link | Posted on Jul 7, 2014 at 18:34 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

Lab D: Nice in theory, but not so much in real life. Sensors of difference sizes simply do not perform the same. Even sensors of the same size can be engineered to perform very different at the same ISOs (A7 vs, A7s).
It is for this reason, as photoguy622 points out, that often if you match DoF, the smaller sensor will have higher IQ. For example, not many larger sensors can match the E-M1's DR at most ISOs. DR translates in to less shadow noise and cameras such as the 800E simply are not 2 stops better at most ISOs even after normalizing resolution.

Sensor performance is a snapshot in time - step back a generation or two and FF *was* two stops better. If someone made a FF sensor with the E-M1's pixel architecture (or equiv) would the two-stops hold?

Direct link | Posted on Jul 7, 2014 at 18:22 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

joeletx: Thank you for clarifying numerous on going debates for a long time. This confirms my understanding the ISO-FL-FStop-EV relationship; that a FT lens 50mm F/2 at ISO-1000 will have the same image exposure (EV) as a FF lens 100mm F/2 at ISO-1000.

Applying the same thing, a FT lens 300mm F/2.8 at ISO-1000 will have the same image exposure (EV) as a FF lens 600mm F/2.8 at ISO-1000.

A FF lens with 600mm F/2.8 is a huge deal financially and physically comparing to a FT lens with same equivalent for wildlife shooting.

I'm not saying one or the other always has the advantage (you also have to consider price, AF performance, weight, etc.) but as the article implies, you have to account for ISO vs. noise *as well as* f/stop. An EM-1+Oly 300mm f/2.8 vs. a Nikon DF +Tamron 150-600mm would give roughly *equivalent* noise performance (and the Nikon+Tamron combo is lighter and 1/2 the price!).

Direct link | Posted on Jul 7, 2014 at 18:11 UTC
On What is equivalence and why should I care? article (2132 comments in total)
In reply to:

RFC1925: I would summarise the article regarding the difference between MFT and FF like this:

If you want:
1) Shallow DOF = FF is better
2) Deep DOF = MFT and FF are tied (FF can compensate with better ISO performance)
3) Portability = MFT is better

All the above have exceptions of course since there are such a great variety of cameras and lenses in both formats.

@BeaverTerror: I did not say anything about the usefulness of shooting smaller than f/22 on FF -- just that it's an area where direct equivalence is usually missing from lenses. (For some reason quite a number of MFT lenses stop down to f/22!)

Direct link | Posted on Jul 7, 2014 at 17:42 UTC
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