ISO

[davichi]

Chia sẻ kinh nghiệm định cư Châu Âu tại Canada

Hiện nay, chính phủ Canada đã đưa ra nhiều chính sách định cư hấp dẫn cho các nhà đầu tư , tuy nhiên việc tìm kiếm những kinh nghiệm định cư Châu Âu, Thẻ xanh Châu Âu tại Canada rất cần thiết giúp bạn nhanh chóng hòa nhập cuộc sống mới tại đây.

Chính sách định cư Canada
Chính sách định cư Canada là điều đầu tiên mà bất cứ ai có nhu cầu đến đây định cư cần phải nắm rõ. Những chính sách định cư thường xuyên có những thay đổi vì thế việc cập nhật những chính sách định cư mới vô cùng cần thiết. Từ năm 2018, người xin nhập cư chỉ cần sống dài hạn ở Canada trong vòng 5 năm gần đây trước khi nộp hồ sơ.

Chính sách định cư Canada là điều đầu tiên cần phải nắm rõ

Nếu có quốc tịch và sở hữu Định Cư Quốc Tế, Thẻ Xanh, Visa, Xuất khẩu Lao Động Châu Âu, bạn sẽ được tự do di chuyển, sinh sống và làm việc không giới hạn tại bất cứ quốc gia nào trong khối cộng đồng chung EU như Đức, Pháp, Italy, Bỉ, Đan Mạch, Thụy Sĩ;… Được hưởng chất lượng hệ thống giáo dục hàng đầu thế giới cũng như chế độ chăm sóc y tế hoàn hảo; Các doanh nhân được tham gia vào môi trường kinh doanh thuận lợi với thị trường chung lớn nhất thế giới. Ngoài ra hộ chiếu Châu Âu cũng là giấy thông hành cho phép công dân châu Âu đi lại không cần visa đến hơn 158 nước trên thế giới.

Định cư Canada có khó không?

Định cư Canada khá khắt khe và khác biệt

Việc định cư Canada khó hay dễ là tùy vào bạn có điều kiện như thế nào hiện tại. Nhìn chung nhập cư Canada không khó như Mỹ nhưng cũng nằm trong top khắt khe vì lượng người muốn xin visa luôn rất cao. Ngoài ra chính sách nhập cư mỗi bang Canada cũng khác biệt.

Cần chuẩn bị gì trước khi định cư?
Trước khi định cư Canada, nhà đầu tư cần chuẩn bị những điều sau để quá trình định cư diễn ra suôn sẻ, nhanh chóng hòa nhập:

• Khả năng tài chính (đối với diện đầu tư và ngay cả diện bảo lãnh người thân, kết hôn thì người bảo lãnh tại Canada cũng phải chứng minh được năng lực tài chính)
• Ý định nghiêm túc định cư lâu dài. Đây là yêu cầu chung đối với bất kỳ quốc gia nào trên thế giới. Thế nên trước khi đưa ra quyết định quan trọng này bạn cần cân nhắc kỹ mình có nên định cư Canada trong nhiều năm tới không.
• Chứng minh sự hiểu biết, phù hợp với văn hóa đủ để hội nhập và định cư Canada lâu dài. Yêu cầu này sẽ càng cần thiết khi chúng ta xin nhập tịch Canada.
• Khả năng ngoại ngữ đủ để giao tiếp trở lên

Xem thêm thông tin tại: Tư vấn Định Cư Quốc Tế, Định cư Châu Âu với thẻ xanh on about.me

 

[Ysarex]

Yes, but.... Higher ISO can also be for action when you want a very fast shutter speed. ISO is raised when you start reducing the amount of exposure applied to the film/sensor. The f/stops in the lens are one variable that controls DOF (depth of field). Given the circumstance you may want more or less DOF. Here's a good reference: Hyperfocal Distance and Depth of Field Calculator - DOFMaster

Joe

 

[mrca]

Raising ISO raises the sensitivity of the sensor enabling it to collect more light. So yes, it can be for low light. But you need to learn how ISO, shutter speed and aperture all work together. You may be shooting in broad daylight but need deep depth of field so an aperture of f8 or f11. If you also need a shutter speed of 1/2000 to stop something in motion, you can raise iso to get a proper exposure. The trade off with raising ISO is the higher you go, the more noise in the image. You might want to take some shots gradually raising the iso and reducing aperture or shutter speed then check to see at what ISO the results are no longer acceptable to you. If you use noise reduction in post processing, you may want to see at what ISO noise is controllable to acceptable levels without loss of too much detail in the image since noise reduction tends to do that. Understand that exposure is built on stops which are doubling or halving the amount of light for each full stop, ie F/2, 2.8, 4, 5.6, 8, 11, 16 and 22. Same for halving or doubling shutter speed or ISO. So if you move one a stop in one direction up or down, you need to move one or both of the other 2 a total of a stop in the other direction.

 

[Ysarex]

Raising ISO raises the sensitivity of the sensor enabling it to collect more light.

ISO does not do that. It has no effect on the light sensitivity of the sensor which is fixed in manufacture and can't be changed.

ISO does two things; one pre-exposure and one post-exposure.

Pre-exposure the ISO value informs the camera's metering system and so causes the meter to suggest an exposure in reference to the ISO value. For example if the ISO value is doubled the meter would suggest an exposure of 1/2 as much light in response. A camera in an auto or semi-auto mode would implement that newly calculated exposure while a camera in manual mode would not unless the photographer makes the change.

Post-exposure the ISO value sets a level of brightening that is applied after exposure to the data recorded by the sensor. Different methods are used depending on the engineered design of the camera. The signal from the sensor can be boosted prior to ADC (Anlog to Digital Conversion) or numerically scaled during ADC and or a combination of both. This is a post-exposure procedure and as such has no effect on the sensor during exposure and so does not modify the sensors response to light intensity.

NOTE: ISO is often described as causing noise in a photograph. The ISO post-exposure process typically suppresses noise in a photo. There are various noise sources -- the two most common are read noise and shot noise. ISO post-exposure processing reduced read noise. Most of the noise people see and find objectionable is shot noise and the source of shot noise is the exposure or rather not enough exposure.

Joe

So yes, it can be for low light. But you need to learn how ISO, shutter speed and aperture all work together. You may be shooting in broad daylight but need deep depth of field so an aperture of f8 or f11. If you also need a shutter speed of 1/2000 to stop something in motion, you can raise iso to get a proper exposure. The trade off with raising ISO is the higher you go, the more noise in the image. You might want to take some shots gradually raising the iso and reducing aperture or shutter speed then check to see at what ISO the results are no longer acceptable to you. If you use noise reduction in post processing, you may want to see at what ISO noise is controllable to acceptable levels without loss of too much detail in the image since noise reduction tends to do that. Understand that exposure is built on stops which are doubling or halving the amount of light for each full stop, ie F/2, 2.8, 4, 5.6, 8, 11, 16 and 22. Same for halving or doubling shutter speed or ISO. So if you move one a stop in one direction up or down, you need to move one or both of the other 2 a total of a stop in the other direction.

 

[mrca]

Joe, thanks for the clarification. As a photographer, for me the only thing that matters to me is the result, crank iso, get more noise and the effect it has on my images as well as the exposure triangle relationship. So if I understand you correctly, bumping iso doesn't increase the light collected by the sensor as say, a higher iso film, but rather, changes how the camera evaluates the exposure? Could you elaborate on " a camera in manual mode would not unless the photographer makes the change." I shoot in manual mode and when I bump iso, I get a different exposure whether I make a change to shutter speed or aperture or not. Is that because the iso setting is altering the metering evalation?

 

[vintagesnaps]

Hi Davichi. The f stop is related to the aperture or size of the lens opening. I'm not sure what you mean by higher; the f stop is larger or smaller. The reason a larger f stop may be used up close is there'd be a more shallow depth of field and usually that seems to be done to have the background more blurred and out of focus. If you wanted to photograph something farther away you'd need to use a smaller aperture to get everything in the scene in focus.

Yes, a higher ISO is usually used in lower light. The ISO is a standardized measurement of light sensitivity. If it's a nice bright sunny day you'd probably set the camera for a lower ISO such as 100/200. If it's cloudy or you're indoors in less (lower) light you'd need to raise the ISO.

The other thing to consider is shutter speed, how fast or slow the shutter is moving. If you use a faster shutter speed, the camera records less light (because the shutter's moving fast and not allowing in as much light). Using a slower shutter speed means more time for light to enter the camera. Usually faster shutter speeds are used when it's bright and sunny, or when photographing movement to avoid blur. I'd suggest a starting point of 1/125 of a second, and eventually you'll figure out how slow a speed you can use hand holding a camera and not get any blur, and how fast a shutter speed you need to capture movement.

When you're figuring out camera settings it's a matter of using the meter (by metering the subject/scene) to let you know if the camera's getting the proper amount of light. The ISO, aperture (lens opening), and shutter speed are all adjusted til the meter shows you're getting the amount of light necessary for a proper exposure.

 

[Ysarex]

Joe, thanks for the clarification. As a photographer, for me the only thing that matters to me is the result, crank iso, get more noise and the effect it has on my images as well as the exposure triangle relationship.

Yep, happy to call it my hang up but I think understanding how it works matters and I'm a teacher by profession so in the classroom I break out the red marker when that triangle stuff comes up. Exposure is the amount of light applied to the film/sensor per unit area and ISO is not an exposure determinant. Exposure = ambient light intensity + f/stop + time.

By giving ISO equal standing in a model with f/stop and shutter speed cause and effect gets confused -- noise for example. ISO doesn't cause noise, underexposing the sensor causes noise. It may sound academic but as I work with my students and watch their behavior I see problems that result from that confusion.

So if I understand you correctly, bumping iso doesn't increase the light collected by the sensor as say, a higher iso film, but rather, changes how the camera evaluates the exposure?

Correct. Digital and film are not the same as regards ISO. Films with higher ISO values really are more light sensitive and for example their DR capacity increases: HP-5 records more DR than FP-4 than Pan-F. Raising ISO on a digital camera is much more analogous to pushing film. You start with an exposure that doesn't give you enough light and with film you overdevelop which helps midtones and highlights but doesn't give you the shadow detail because you didn't expose for it. With digital the camera electronics take the data the sensor does record (less data = less DR) and brightens it up to compensate but you get no additional reach into the shadows -- only increasing exposure can do that.

Could you elaborate on " a camera in manual mode would not unless the photographer makes the change." I shoot in manual mode and when I bump iso, I get a different exposure whether I make a change to shutter speed or aperture or not. Is that because the iso setting is altering the metering evalation?

No. In fact if you shoot in manual and do not change the f/stop or shutter speed when the ISO is changed you do not get a different exposure. You get the same exposure. Changing the ISO gives you a different level of image brightening as a post processing result.

I know this can sound real nit picky but it can matter. Exposure and only exposure (f/stop + shutter speed) determines what data you will record. What ISO does is a post process that occurs after the exposure has been completed. So a high ISO value will take the same exposure and brighten it more than a lower ISO value, eg. more gain applied to the sensor signal for the higher ISO value, but it's working with the data that's already been collected by the sensor and it can't create data that didn't get recorded in the first place. So if for example you really do need to reach deeper into the shadows you can only do that with exposure -- ISO can't help with that.

That uncovers the fallacy of the exposure triangle. Consider:

1/250 sec + f/5.6 + ISO 800
1/125 sec + f/8 + ISO 800
1/500 sec + f/2.8 + ISO 400

Exposure triangulators would claim all three of the above are the same exposure. They're not. One of those exposures records more shadow detail and more DR than the other two because the exposure is different -- it's twice as much.

Joe

 

[Jeff15]

Leave the ISO on auto, problem solved...........

 

[ac12]

@davichi
I would recommend that you take a photo class or classes, to teach you the basics of photography both from technical and artistic angles.
Or you can look for a beginners photography book, to try to do similar.

The BIG advantage with a class, is that you can ask questions to the instructor, and get one-on-one help. You cannot get this level of help from the internet, at least not easily. Also you can work with fellow students to work out a problem, which I find more enriching than being told the solution by the teacher. I've also seen where a student that understands the instructor, will translate/paraphrase the instructor to a fellow student, in a way that the fellow student understands.

There are classes that you can take from community colleges, city parks and recreation, art centers, photo stores, and local photo clubs. I enjoyed the photo class at my local community college.

Gud Luk

 

[vintagesnaps]

I never did think calling exposure a triangle to be the best way to describe it because what does a triangle have to do with it? this isn't geometry...

I am a longtime film photographer so I tend to think of it in terms of film. So I get that the film ISO indicates actual light sensitivity in the film emulsion, and a digital camera is recording light in a different way. Can't say I understand all the technology of that, but to me it seems like the exposure is still affected by the ISO setting because other settings (shutter speed, aperture) would need to be adjusted accordingly to get a proper exposure.

I agree, taking a class in person would be a wonderful idea.