Now read the values \u200b\u200breported on the objectives it is almost a business, especially for those who are not kept informed during the transition from film to digital.
To explain these difficulties we must put an introduction and explain the concept of equivalence is often mentioned in relation to photographic lenses.
First you must place the meter, the unit of reference for the focal lengths of camera lenses which for us is the data that are relative to the field that moves a lens on 35mm film, the Kodak film classic that is. Complicated?
In practice we take for example a 50mm lens in the photo that is considered "normal" because it roughly mimics the shot that we see in plays to the naked eye and photographic film. From now on this will be the reference for the 50mm wide field of view.
Today, however, the film no longer exists, using sensors and are of many different sizes, carry an explanatory chart that I posted to understand the magnitude of the sensors over film:
Here we summarize the sizes in mm:
| Sensor Type | Width | Height | Format |
|---|---|---|---|
| 1 / 3, 6 " | 4mm | 3mm | 4 / 3 |
| 1 / 3, 2" | 4.536 mm | 3,416mm | 4/3 |
| 1/3” | 4,8mm | 3,6mm | 4/3 |
| 1/2,7" | 5,371mm | 4,035mm | 4/3 |
| 1/2,5" | 5,76mm | 4,29mm | 4/3 |
| 1/2" | 6,4mm | 4,8mm | 4/3 |
| 1/8" | 7,167mm | 5,319mm | 4/3 |
| 1/1,7" | 7,6mm | 5,7mm | 4/3 |
| 2/3” | 8,8mm | 6,6mm | 4/3 |
| 1" | 12,8mm | 9,6mm | 4/3 |
| 4/3" | 18mm | 13,5mm | 4/3 |
| Canon APS-C | 22,2mm | 14,8mm | 3/2 |
| Nikon DX - Sony APS-C | 23,7mm | 15,7mm | 3/2 |
| Canon APS-H | 28,7mm | 19,1mm | 3/2 |
| 35mm Film / Full Frame | 36mm | 24mm | 3 / 2 |
Another picture on the fly to understand the magnitude of the different sensors:
And yet, to try to simplify the discussion:
In the picture above the comparison between the lens focal reflex on 35mm film, with the corners of the field in gray in the image on the left column. In the right column the result of multiplication of the same lenses, mounted on a DSLR with 1.5 multiplication factor X. (documentation Tamron
What about changing the size of the sensor? Simple, the angle of which is to be structured and how change has an impact on this objective? Simple, every company has continued to write on them the actual mm but not the same as they would have with the film have created so much confusion.
practical example, I use Olympus and the Olympus sensor is half the size of photographic film, it follows that the multiplication factor (a concept I will explain better) to apply to the number written on the target is 2. In practice, reading the specs of a lens if I can find written Olympus 12-60mm (zoom) X 2 will have to increase those numbers to know the focal length of the lens than the analog film to finally reach a 24-120mm equivalent coverage.
I know, now is a mess but once you understand the mechanism and everything will be easy to make a choice J , because each brand has its own multiplier!
All this has brought an incredible chaos because a novice user would expect that if a law is and what is number one without having to just get a deal but it is unfortunately.
returned to make a practical example, assume that we want to photograph a bird in hand and that we have a film camera with a 400mm lens and an Olympus digital, on the latter, to get the same shot will be enough to mount a 200mm lens, because as said before the lens becomes a 400mm under the 2X multiplier. What does this mean? Simply that if the objective of the analogue machine weighs 1kg and we say it is 40cm long and weigh that Olympus will be half the size easier to handle.
The only machines that do not need multiplications of these are full frame, so named because they have a sensor as large as the old film camera, all the other mountain smaller sensors and instead must act accordingly with their number multiplication.
all at first glance may seem a bit complicated and certainly can be confusing but do not worry, life intervenes to complicate the concept of depth of field ... but that'll do another intervention J
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