An 18-55 is a 3X zoom.18 X 3=54. The X in 3X stands for "times".If you wanted a 10X zoom you'd want an 18-180.A member of the rabble in good standing...
LM1 wrote:.
An 18-55 is a 3X zoom.18 X 3=54. The X in 3X stands for "times".If you wanted a 10X zoom you'd want an 18-180.A member of the rabble in good standing..
Great!.
Thanks LM1.
So large figure divided by small figure is zoom?I am being silly.. but what actually are 18 and 55?.
If I shoot at 18, does that mean I am shooting at 1x optical zoom?..
The Indian PhotoGrapher wrote:.
Great!.
Thanks LM1.
So large figure divided by small figure is zoom?I am being silly.. but what actually are 18 and 55?.
If I shoot at 18, does that mean I am shooting at 1x optical zoom?.
The 18 is in millimeters and describes the focal length of the lens. The focal length tells you something about how wide a field of view is for that lens on your camera. 18mm is moderately wide angle. and 30mm to 35mm is about what most people think of as "nomal" or approximately what the human eye sees. The higher the number the more telephoto (acting like a telescope is one way of thinking of it) the lens is..
Zoom factor is only describing the range of the zoom lens. There are telephoto zoom lenses like 70-210 which would also be a 3X zoom lens. A 1X zoom would be a zoom without zoom, otherwise known as a prime lens of only one focal length.A member of the rabble in good standing...
The Indian PhotoGrapher wrote:.
So large figure divided by small figure is zoom?.
Yes ... now don't people sound silly when they demand 8X or 10X zoom ? They don't realize that they're specifying *range* and not magnification ! (It's not like binoculars where 7X specifies a degree of magnification)..
I am being silly.. but what actually are 18 and 55?.
As mentioned, that's the focal length of the lens in mm which has a direct correlation on how big the image is projected onto the sensor ... imagine your dog out in the backyard 20' away. With a 7mm lens (which you might find on a digicam) he's really small; with an 18mm lens, nearly 3X bigger, at 55mm, 3X bigger than that; with a 400mm lens, huge ! But the degree to which he fills the frame depends on the size of the sensor, too..
One thing that's been suggested is to treat as "normal" or 1X, a lens whose focal length is the same as the diagonal measurement of the sensor. On 35mm (or a "full frame" DSLR, this would be around 43mm - a 50mm lens is considered standard) while on APS-C, it would be 28mm. So then an 18-55mm zoom would be a .65X - 2X zoom..
But what's actually done is to express focal lengths of lenses in terms of "35mm equivalents" ... that is, what lens, used on 35mm, gives you the same field of view. So the 7.8-23.4mm lens on your CP7900 is "equivalent" to a 38-114mm used on a 35mm camera (equivalent as far as "field of view" or how much your subjects fill the frame). APS-C cameras have a 1.5X "crop factor" ... multiple 18-55 by 1.5 and that lens is similar to a 27-82mm lens used on 35mm (full frame or film). That's fine if you're used to what you get with those focal lengths on film ! But now you can also compare it to what you're used to with your CP7900 ...
The 18-55 or 18-70 give you much better wide angle coverage, while the 18-55 is lacking on the tele end and the 18-70 comes close..
- DennisGallery at http://kingofthebeasts.smugmug.com..
Just to make sure you understand,.
As soon as you will feel that 55mm end is not enough, you can buy telephoto lens that will perfectly work with D40 body!.
I've seen couple photographers who discovered lens interchangeability for DSLR after 2 years of photography..... No. You can use different lenses on D40!!!!.
This is tread list where you can get most accurate answer: http://forums.dpreview.com/forums/forum.asp?forum=1030.
Http://www.stan-pustylnik.smugmug.com..
Is the Nikon D40, a 35mm format camera?.
I understand that the wide angle, normal or telephoto categorization depends on the focal lengh of the lens and the camera format?..
D40 is Digital SLR (DSLR) camera with 1.5 crop format. you should multiply focal lenth by 1.5 to get approximate analog with film SLR lens..
For example 50mm lens will provide same angle of view as 75mm lens on film SLR body..
20mm same as 30mm with film SLR.
100mm - same as 150mm with film SLR.
300mm - same as 450mm with film.
With telephoto it is advantage, with wide angle - disadvantage..
Http://www.stan-pustylnik.smugmug.com..
I recently replied to another poster with a similar question. Click on the link to read my reply.
Http://forums.dpreview.com/...forums/read.asp?forum=1002&message=24282553.
Hope this helpsbecksi.
The Indian PhotoGrapher wrote:.
Hi.
I am a new bie!!.
I had a Nikon CP7900 which has 3x optical zoom.
I recently bought the Nikon D40 with the 18-55 standard lensHow much zoom does the 18-55 has? How do we calculate the zoom?..
The Indian PhotoGrapher wrote:.
What is the difference between Zoom and Magnication?.
Dennis answered that question in his post..
Zoom is the ratio of the longest focal length divided by the shortest and gives an indication of the range of the lens..
Magnification is the ratio between the size of an object in the image produced by the lens divided by the size of the same object as seen by the naked eye, i.e. as produced by a "normal" lens. On your D40 a "normal" lens is about 30mm focal length, so a 55mm lens would produce an image with about 1.8 times magnification.Chris R..
Thanks for all the replies.. I really appriciate your assistance in explaining these concepts to me!!.
I have a better understanding now .. Thankyou to you.
However still a few more questions.
The 18 is in millimeters and describes the focal length of the lens. The focal length tells you something about how wide a field of view is for that lens on your camera. 18mm is moderately wide angle. and 30mm to 35mm is about what most people think of as "nomal" or approximately what the human eye sees. The higher the number the more telephoto (acting like a telescope is one way of thinking of it) the lens is..
18 mm is the rear end of the Lens. This describes the focal length of the lens..
What is 55 mm?.
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Zoom factor is only describing the range of the zoom lens. There are telephoto zoom lenses like 70-210 which would also be a 3X zoom lens. A 1X zoom would be a zoom without zoom, otherwise known as a prime lens of only one focal length..
Zoom factor = Range.
1x zoom = prime lens of only one focal length!.
Do we have lenses like this in the market? or did you write this to explain what 1x is?Why would anyone use such a lense?.
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One thing that's been suggested is to treat as "normal" or 1X, a lens whose focal length is the same as the diagonal measurement of the sensor. On 35mm (or a "full frame" DSLR, this would be around 43mm - a 50mm lens is considered standard) while on APS-C, it would be 28mm. So then an 18-55mm zoom would be a .65X - 2X zoom..
Diagonal measurement of the sensorI have a D40. What is the "diagonal measurement of the sensor".
Is this also measured in mm?.
Is this what you call the format of a camera? Like like we say "35mm format camera?".
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As mentioned, that's the focal length of the lens in mm which has a direct correlation on how big the image is projected onto the sensor ... imagine your dog out in the backyard 20' away. With a 7mm lens (which you might find on a digicam) he's really small; with an 18mm lens, nearly 3X bigger, at 55mm, 3X bigger than that; with a 400mm lens, huge ! But the degree to which he fills the frame depends on the size of the sensor, too..
But what's actually done is to express focal lengths of lenses in terms of "35mm equivalents" ... that is, what lens, used on 35mm, gives you the same field of view. So the 7.8-23.4mm lens on your CP7900 is "equivalent" to a 38-114mm used on a 35mm camera (equivalent as far as "field of view" or how much your subjects fill the frame). APS-C cameras have a 1.5X "crop factor" ... multiple 18-55 by 1.5 and that lens is similar to a 27-82mm lens used on 35mm (full frame or film). That's fine if you're used to what you get with those focal lengths on film ! But now you can also compare it to what you're used to with your CP7900 ...
The 18-55 or 18-70 give you much better wide angle coverage, while the 18-55 is lacking on the tele end and the 18-70 comes close..
I really liked your explanation for 35mm equivalents.So if the Sensor size is small, the "magnification" will be small.what is the size of the sensor of the D40?Crop factor? How do we define it?.
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D40 is Digital SLR (DSLR) camera with 1.5 crop format. you should multiply focal lenth by 1.5 to get approximate analog with film SLR lens..
Approximate analog with film SLR lens. >> 35 mm format?.
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Magnification is the ratio between the size of an object in the image produced by the lens divided by the size of the same object as seen by the naked eye, i.e. as produced by a "normal" lens. On your D40 a "normal" lens is about 30mm focal length, so a 55mm lens would produce an image with about 1.8 times magnification..
Very interesting!!.
Thank you.
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I'm not sure I can tell which are the newest questions, but I'll take a stab:.
The Indian PhotoGrapher wrote:.
What is 55 mm?.
The zoom lens is 18mm at the wide end and 55mm at the telephoto end and you can set it at either point or anywhere in between. You can convert each of those values to "35mm equivalent" or "magnification" as per my other post..
Do we have lenses like this in the market? or did you write this toexplain what 1x is?Why would anyone use such a lense?.
A basic lens has a single focal length. It magnifies the subject to some degree. Think binocular, telescopes, eyeglasses. Zoom lenses are much more complex, with optical elements that move back & forth as the lens "zooms" to yield varying focal lengths..
As a rule of thumb, the greater the range of a zoom lens, the lower the resulting image quality and the "slower" the lens. (Slower meaning smaller apertures, making it less appropriate for low light/sports/wildlife photography). So you can have high quality f/1.4 and f/2 prime (fixed focal length) lenses; f/2.8 lenses that are 3X zooms (like 28-70) f/4 lenses that are 4X & 5X zooms and when you increase the zoom ration further, you end up with lenses that are f/5.6 or even f/6.3 over parts of their range (like the Tamron 18-250 which is a 14X zoom). Plenty of caveats apply; it's easy to make broad-range zooms faster for smaller formats, so the 4:3 system from Olympus has f/2 zooms and compact digicams have wide-ranging lenses with fast lenses..
Diagonal measurement of the sensorI have a D40. What is the "diagonal measurement of the sensor".
About 28mm..
Is this also measured in mm?Is this what you call the format of a camera? Like like we say "35mmformat camera?".
Not exactly. 35mm is the width of the roll film originally designed for moves that was adopted for those cameras. The picture area on the film is actually 24mm x 36mm (also the same size as "full frame"). The film is 35mm wide, which accomodates the 24mm picture area width plus room on the sides for the sprocket holes..
Other film formats use the film size, like 645 (6x4.5cm), 6x6 (also cm), 6x7, etc. And then large format does the same, but measured in inches (4x5, 5x7, 8x10, etc.). There were plenty of old film formats which used a numerical name; 110 and 126 may be familiar; 127 & 620 & lots of others less so. I don't know where most of the names come from..
The "format" is more or less a name that specifies the size of the film or sensor. So with DSLRs, we have 4/3, APS-C (Canon's APS-C is a 1.6X crop, slightly smaller than the Nikon/Sony/Pentax 1.5X crop), Canon's larger 1.3X sensor (I don't know if there's another name for the format other than 1.3X), "full frame"..
I really liked your explanation for 35mm equivalents.So if the Sensor size is small, the "magnification" will be small.what is the size of the sensor of the D40?.
APS-C. 16mmx24mm. 28mm diagonal..
Crop factor? How do we define it?.
It's a simple multiplier used to understand what FOV you get from a lens compared to what you'd use on 35mm. If you're not already famililar with 35mm, you can probably conveniently ignore crop factors ... except that it's still useful for comparing to digicam lenses, which are frequently expressed in both actual and "35mm equivalents"..
A 28mm lens on the D40 is "equivalent" (in terms of what you capture) to a 42mm lens on a 35m camera ... 28x1.5 = 42..
Approximate analog with film SLR lens. >> 35 mm format?.
Yes..
Hope that helps ! It's pretty important to understand what you want to buy for lenses. For instance, I use a 28-75/2.8 lens for "people photography". 28-75 is "equivalent" to 42-112 on a 35mm camera. 42mm is very slightly wide angle (actually, it's very close to 'normal' but we're used to a very slightly telephoto 50mm lens as 'normal' so 42mm seems slightly wide). Not wide enough for 'group shots' but wide enough to get an entire child's body in the frame indoors if you can back up a bit. The classic range for candids/portraits is in the 85 to 135mm range, so 112mm falls within there nicely.
I have a wide angle lens that overlaps that range. I could have skipped the 28-75 in favor of a wider zoom (like 18-50) and a tele zoom, but then I'd be constantly changing lenses while photographing people. I also could have gone for a wider range zoom (18-125 or 24-105) but those lenses are slower, and the f/2.8 zoom lets me (a) shoot with less depth of field - i.e. out of focus backgrounds and (b) shoot with faster shutter speeds in low light..
Probably a little overwhelming, but you can see why there are so many lenses on the market ! Every photographer has different needs, and every lens has compromises..
- DennisGallery at http://kingofthebeasts.smugmug.com..
It is a little tricky in your reply to identify the questions that you are now asking, so apologies if I have missed any.The Indian PhotoGrapher wrote:[snip].
What is 55 mm?.
This is the focal length when the 18-55mm lens is at maximum zoom. With a very simple lens with a single optical element this would be the distance between the back of the lens and the point at which the light is focused - the point at which you would place the sensor. Modern lenses are complex with multiple elements so the actual distance is unlikely to be 55mm..
[snip].
Do we have lenses like this in the market? or did you write this toexplain what 1x is?.
Yes, there are many prime lenses available including for you D40x..
Why would anyone use such a lense?.
Prime lenses are cheaper and lighter than zoom lenses. More importantly, they offer the best possible optical quality. Many photographers on this forum use prime lenses only, and most will own at least one prime - I have a 50mm prime. The disadvantage is that you have to move forward or backwards to compose the picture, and you would normally carry several primes around with you..
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[snip].
I have a D40. What is the "diagonal measurement of the sensor".
Is this also measured in mm?.
This is from the Learn/Glossary section of this site:http://www.dpreview.com/...learn/?/Glossary/Camera_System/sensor_sizes_01.htmYour D40 has the same sensor size as the Nikon D70 and D2X..
Is this what you call the format of a camera? Like like we say "35mmformat camera?".
More or less..
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[snip].
So if the Sensor size is small, the "magnification" will be small..
No. The opposite. A 30mm focal length lens will effectively produced a more magnified image on a smaller sensor than it will on a larger sensor because the field of view will be much smaller..
What is the size of the sensor of the D40?.
See link above. All Nikon, Fuji, Pentax, Samsung and Sony (currently) DSLRs have an "APS-C" sonsor with a 1.5 times crop factor. Olympus DSLR's have a crop factor of 2.0. Canon DSLR's have varying crop factors, including "full frame" sensors which are the same size as 35mm film..
Crop factor? How do we define it?.
Crop factor is only used for larger sensors, mainly in DSLRs. (Compact cameras have a very complex method of describing the sensor size which is described in the link above.) The crop factor is the area of sensor divided into the area of a 35mm film. It is calculated this way so that if you multiply the lens focal length by the crop factor you get the focal length equivalent on a 35mm film camera..
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D40 is Digital SLR (DSLR) camera with 1.5 crop format. you shouldmultiply focal lenth by 1.5 to get approximate analog with film SLRlens..
Approximate analog with film SLR lens. >> 35 mm format?.
I am not sure what you mean by this question..
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Chris R..
Chris R-UK wrote:.
[snip].
So if the Sensor size is small, the "magnification" will be small..
No. The opposite. A 30mm focal length lens will effectivelyproduced a more magnified image on a smaller sensor than it will on alarger sensor because the field of view will be much smaller..
In the context of the snipped portion ... in small sensor digicams, with zoom lenses with ranges like 7-23mm, the magnification (i.e. the size of subject matter projected by the lens onto the sensor) is much smaller; it doesn't need to be big to "fill the frame" because the frame is smaller. So whether magnification is small or large depends on what magnification you're talking about. The lens projects an image that's magnified by a degree that depends on the focal length. A 30mm lens projects the same size subject onto the sensor regardless of whether it's on a small sensor digicam, APS-C, full frame, medium format, etc.
So a 30mm lens is a 30mm lens no matter what it's designed for and that dictates magnification at the film/sensor plane..
The degree to which it fills the frame is dependent on the sensor size; it fills a smaller frame to a greater degree. (And so, small sensor cameras use lenses that magnify less). You can get an idea of what to expect from a given lens by either converting all lenses to an "equivalent" using a common frame size (35mm equivalent) or by converting all lenses to "percent of diagonal"..
And just to cut off the suggestion - the reason actual focal lengths are still important is for depth of field calculations and, in the case of interchangeable lenses, because they can be used on cameras with varying sensor sizes..
Look at it like this ... imagine you're in your living room with a slide or movie projector setup. You can put a lens on the projector that makes the picture small - you can put a lens on the projector that makes the picture huge - in particular, keep in mind that everything you see in the frame is bigger than it was with the other lens. That's focal length. Now consider the screen. Imagine a screen that's as big as the projected image.
Now put up a screen that's only half as big. The sizes of the 'things' in the picture don't change. But the things that are still on the screen fill the screen much more. Things are twice as big relative to the smaller screen. That's your smaller sensor ...
Print both pictures to 4x6 or 8x10 and everything looks bigger in the picture from the smaller sensor..
- DennisGallery at http://kingofthebeasts.smugmug.com..
It is remarkably difficult in this thread to explain concepts simply and concisely, especially when you have to avoid using terminology which will not be familiar to the original OP.Chris R..
I agree ! I feel like between some of us, we've just rewritten what must be a basic FAQ Your reply was certainly correct, but in the context of what I'd written, I'm not sure the OP even knew what he was asking regarding magnification..
The 4X terminology for expressing zoom range is so bizarre & misleading; it's somewhat useless as it doesn't describe either the wide or tele capability of a lens; it's misleading, because it's intended to imply magnification (at least in consumer digicams). OTOH, newbies may very well be accustomed to similar specs on binoculars where it means magnification..
We've been through the alternate proposals on these forums enough times to know they're impractical; the only real solution is an educated consumer, so good for the OP trying to understand this !.
(BTW, the best way to understand this is probably the good old comparison photos showing what you get from various focal lengths ... I don't think I've seen one of these done expressly for APS-C but I remember them from lens brochures)..
- DennisGallery at http://kingofthebeasts.smugmug.com..
Thank you everyone!!!.
I have a much better idea about zoom and magnification and also learnt a lot of new things along the way!.
Thank you everyone.
You folks rock!!..