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What is the ( x ) Power of those Lenses?
Hi All..

Coming from P&S background, I am used to measure zoom (Optical or Digital) with X as in 4x, 200x, etc..

But now with DSLRs Lenses are measured with length (70-200mm)..

How can I compare the two type of zooms?.

What is 4x in mm?.

VidER.

I Shoot for Fun!..

Comments (28)

With the zoom on an SLR you would divide the first number , inyour 70-200mm example divide the 200 by 70 and you would about 2.85 X. Take onne of you P&S cameras and get the rane off of the lens and divide the lower number into the larger number and see if it doesn't match up to the 3 X or 4 X it is supposed to be.Ralff..

Comment #1

I dont think you can compare x to mm..

All x means is that the long end of the lens it x times the short end.... ie 100-400mm lens is 4x zoom!! AFAIK..

Comment #2

Trouble is, those x figures are meaningless unless you know what they start at..

For example, a 12-24 lens is 2x (longest divided by widest). A 200-400 lens is also 2x. However, what you see through the viewfinder is VASTLY different between the two..

"Most" of the compact digicams start at around 35mm, 38mm. So you can MOSTLY assume that when they are talking about a "3x lens", they probably mean roughly 35-105mm equivalent...

Comment #3

4X means nothing in milimeters.The zoom ratio is just a ration..

4x can be 25-100 mm and 100-400 mm or everything that the ratio of the extremities is 4.VictorBucuresti, Romaniahttp://s106.photobucket.com/albums/m268/victor_petcu/http://picasaweb.google.com/teodor.nitica/..

Comment #4

It doesn't really compare the same way as point and shoot. Most point and shoots, because of small sensors, have very low focal lengths for their wide angle, like 6mm. So can show many "Xes"..

A 200-400 zoom for a DSLR is only 2x, but that's a lot of reach and difference from 200 to 400..

The only ones that might compare are the radical wide to tele zooms for SLRs like an 18-200 which would be 11X. But a tele to tele like the (3X) 70-200 is not found on point and shoots...

Comment #5

VidER wrote:.

Hi All..

Coming from P&S background, I am used to measure zoom (Optical orDigital) with X as in 4x, 200x, etc..

But now with DSLRs Lenses are measured with length (70-200mm)..

How can I compare the two type of zooms?.

What is 4x in mm?.

Take the longest part of the zoom (200mm in the example you gave) and divide it by the shortest part of the zoom (70mm in the example you gave)..

200 divided by 70 equals 2.86. Let's call it 3. So a 70-200mm lens has a 3x zoom factor..

A 24-70mm lens also has a 3x zoom factor (70/24=2.92), but it starts shorter and ends shorter than the 70-200mm..

For some situations, you might prefer the 3x zoom factor of the 24-70mm (walking around in an African village where wide shots are more useful than telephoto shots)..

For other situations you might prefer the 3x zoom factor of the 70-200mm with it's longer telephoto, and be willing to sacrifice the wide angle. That's the nice thing about DSLRs, you can choose which of the many 3x zoom factor lenses you need for the situation..

Or you could choose the Sigma 50-500mm, a 10x zoom (500/50=10), but you'd have to live with a lens that's almost 2 feet long when extended and weighs 4 pounds..

That's why DSLR users tend to ignore the zoom factor and choose a lens that has the range they need for the assignment...

Comment #6

I would calculate this a different, but incorrect, way!.

Since 50mm is about the view of the human eye (for a ff camera), assume 50mm is 1x, then a 200mm lens is 4x, and a 70 - 200mm zoom would be 1.4x to 4x..

On the wide angle front, a 25mm lens is 1/2 x. Though maybe not conventional, it makes sense..

Of course for a cropped sensor (1.6x), the 70-200mm would be a 2.2x to 6.4x..

This is not the range of zoom (as is advertised on p&s), but it gives way moreinformation..

Jeff..

Comment #7

This post is misleading.Jules.

Richardwigley wrote:.

I dont think you can compare x to mm..

All x means is that the long end of the lens it x times the shortend.... ie 100-400mm lens is 4x zoom!! AFAIK.

Why can't you blow bubbles with chewing gum?..

Comment #8

Jeff Q wrote:.

I would calculate this a different, but incorrect, way!.

Since 50mm is about the view of the human eye (for a ff camera),assume 50mm is 1x, then a 200mm lens is 4x, and a 70 - 200mm zoomwould be 1.4x to 4x..

On the wide angle front, a 25mm lens is 1/2 x. Though maybe notconventional, it makes sense..

Of course for a cropped sensor (1.6x), the 70-200mm would be a 2.2xto 6.4x..

This is not the range of zoom (as is advertised on p&s), but it givesway moreinformation..

Jeff.

Too bad this nomenclature hasn't moved into mainstream use because it does actually convey useful information...

Comment #9

When a manufacturer says that one of their cameras has a "4X" lens, that does not indicate the "power" of the lens. They are jerking us around. If they can put "4X" then "5X" then "6X" on their camera boxes, they know that we, being idiots, will soon conclude that the "6X" box must hold something better than the old "4X" box (last year). They do the same thing with the number of pixels..

The "4X" is just a ratio of the largest FL / smallest FL. It's not used as much in reference to removable-lens cameras as with fixed-lens cameras. That is probably because the marketing departments believe that it would backfire (many dSLR photographers are more technically competent than those with cheap compact DC's bought at big-box stores)..

When taking "macro/micro" pix, we often refer to the "magnification ratio" in similar terms. Don't get confused..."Mag ratio" is totally different than "Zoom ratio"..

VidER wrote:.

Hi All..

Coming from P&S background, I am used to measure zoom (Optical orDigital) with X as in 4x, 200x, etc..

Wow! a 200X zoom ratio! .

But now with DSLRs Lenses are measured with length (70-200mm)..

Stating the min/max FL is more informative. You can easily perform the division to get the "Zoom Ratio" if you want to. It tells you the ACTUAL focal lenths! To help you get really confused, some people refer to "Effective FL". This is the FL of a lens on a 35mm film camera that gives the same Field-of-View (FOV). There is an associated "Crop Factor" that tells the ratio between the full frame (35mm) camera and the camera with a smaller sensor. For example, Oly has a 2.0 CF...Canon has a 1.6 CF...Nikon/Pentax/Sony have a 1.5 CF.

I don't understand this, because marketing guys like big numbers and since CF is an "upside-down" parameter (ie, bigger numbers are worse), they should be giddy with the really big CF on tiny sensors, like the popular 1/2.5" variety. .

Charlie DavisNikon 5700, Sony R1, Nikon D300HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/'Experience: Discovering that a claw hammer will bend nails.Epiphany: Discovering that a claw hammer is two tools...'..

Comment #10

Ok... my bad!.

JulesJ wrote:.

This post is misleading.Jules.

Richardwigley wrote:.

I dont think you can compare x to mm..

All x means is that the long end of the lens it x times the shortend.... ie 100-400mm lens is 4x zoom!! AFAIK.

Why can't you blow bubbles with chewing gum?..

Comment #11

Like others have mentioned, it can't really be compared properly, since "3x zoom" doesn't actually tell you where the zoom range starts or ends, just that the lens can zoom in 3 times compared to it's most "zoomed out" position. The rating of SLR lenses however actually give you a proper understanding of what the focal distance is of a lens..

To use an analogy..

Imagine I told you that today I had 3 times as much money in my wallet as I did yesterday. This is the P&S method. You don't actually know how much money I have in my wallet, just that it's 3 times as much as yesterday. Yesterday I could have had $10 in my wallet, or $500, or $0.01..

In the case of SLR lenses however, I would say instead that yesterday I had $35 in my wallet, and today I have $105. Thats still 3 times as much today as yesterday, but you actually also know the precise amount of money on both days as well...

Comment #12

As well as the P&S stating the lens description in terms like 3x or 10x, there also seems to be an emphasis on the maximum zoom. That is "how big does it make things"..

Say you have a 5x zoom lens on two different cameras. Lets say one is a 24 to 120mm lens, the other is 40 to 200mm..

Both are 5x (120/24 = 5 and 200/40 = 5). And the makers often seem to emphasise the longest end of the range. Here one is 120mm and the other is 200mm. Which one sounds better?.

What is rarely emphasised is the starting point at the wide-angle end of the range. Using the same example, one lens starts at 24mm, the other at 40mm. Now which one sounds better?.

It's not always obvious to beginners, and the manufacturers do little to help, that the wide-angle range can be the most-used, most interesting and most important part of the zoom range. If you are taking a picture in a cramped interior, or outdoors trying to photograph a building, the wide-angle capability is extremely useful..

I'm sure many experienced photographers would prefer the 24mm to 120mm lens in this example (though ultimately it is personal preference)..

Here is a useful site for seeing the effect of different focal length lenses: http://www.tamron.com/...es/learning_center/tools/focal-length-comparison.php.

Regards,Peter..

Comment #13

I would endorse most of what has been said so far..

One additional observation. All P & S cams have fixed general purpose lens. Most start at around 35-38mm (35mm equivalent). Only a few start at 28mm. Given that the starting point is fairly common to all a figure of 4x or 10x makes some sense. With interchangeable lenses on a DSLR it has very little value..

That said I commonly advise people to get an 18-70 mm lens rather than 18-55 because the extra focal length (4x rather than 3x) is very useful! So it has some use with DSLR when comparing specific similar lenses..

Chris Elliott.

*Nikon* D Eighty + Fifty - Other equipment in Profile.

Http://PlacidoD.Zenfolio.com/..

Comment #14

Why was what richard said misleading? Sounds right and pretty much echoes what others have said. His first statement is right, w/o knowing more information, the "X" factor is kind of useless, esp when trying to compare different zoom lenses. And his 2nd statement sounds right to me as well..

Richardwigley wrote:.

Ok... my bad!.

JulesJ wrote:.

This post is misleading.Jules.

Richardwigley wrote:.

I dont think you can compare x to mm..

All x means is that the long end of the lens it x times the shortend.... ie 100-400mm lens is 4x zoom!! AFAIK.

Why can't you blow bubbles with chewing gum?.

Just trying to learn.

Blog: http://novicephotog.blogspot.com/Flickr: http://www.flickr.com/photos/9778447@N07/..

Comment #15

Take your dslr zoom, with a lens that incorprates a 'standard' FL and hold the camera I a vertical position..

If you are lookng through the viewfinder with your left eye, keepthe right one open as well. Zoom in an o something like a windo on a house across the road and move the zoom until the image from each eye isthe same size. By controlling the aim of the camera you shou be able to see in 3dalmost like you were looking at somethin without the camera and usin both eyes.Take a shot..

Lookat the info and see what FL you took it at. On my D200 it's 55mm. This is what I call 1x. Do the same thing again and get the window (flag, postbox whatever) to be exactly twice the size of the view seen with your right eye (or the eye ot looking through the camera).Repeat and check the FL.That to me is 2x..

Although some lenses do seem to talk about the magnification from it's widest setting to the lngest I think thisis confusing the situation. The 'times' factor should relate to the 'standard' ie 1x1 view and not to the widest view of that particular lens.Jules.

Why can't you blow bubbles with chewing gum?..

Comment #16

Guidenet wrote:.

It doesn't really compare the same way as point and shoot. Most pointand shoots, because of small sensors, have very low focal lengths fortheir wide angle, like 6mm. So can show many "Xes"..

Oh dear!.

P&S's and dSLR's are the same in terms of zoom ratio. So 100 - 400 mm is x4 and 3 - 12 mm is x4 and 6 - 25 mm is x4. It doesn't matter where it starts from..

A 200-400 zoom for a DSLR is only 2x, but that's a lot of reach anddifference from 200 to 400..

Seems the same to me....

The only ones that might compare are the radical wide to tele zoomsfor SLRs like an 18-200 which would be 11X. But a tele to tele likethe (3X) 70-200 is not found on point and shoots..

True but nowt to do with the original point or question. And 70 - 200 mm would be wide angle to normal on some cameras... 'though I've never seen a lens with that sort of coverage..

Just my 2d worth..

Regards, David..

Comment #17

Dennis Phillips wrote:.

Jeff Q wrote:.

I would calculate this a different, but incorrect, way!.

Since 50mm is about the view of the human eye (for a ff camera),assume 50mm is 1x, then a 200mm lens is 4x, and a 70 - 200mm zoomwould be 1.4x to 4x..

On the wide angle front, a 25mm lens is 1/2 x. Though maybe notconventional, it makes sense..

Of course for a cropped sensor (1.6x), the 70-200mm would be a 2.2xto 6.4x..

This is not the range of zoom (as is advertised on p&s), but it givesway moreinformation..

Jeff.

Too bad this nomenclature hasn't moved into mainstream use because itdoes actually convey useful information..

Hi,.

But FoV is often quoted and gives the answer regardless of format. So 45 FoV for a mini P&S and for a 10" x 8" cut film monster are the same. Better to quote degrees imo..

And could someone please explain about the human eye having about 160 FoV? I'm tired of doing it..

Try this test. Cut a hole 24 mm by 36 mm in a piece of card and hold it 50 mm in front of your eye. That's the view you get from a 50 mm lens on a 35 mm film camera and most people will see that it cuts off a lot of the eye's FoV. If it doesn't you've problems, like tunnel vision..

Regards, David..

Comment #18

Unfortunately, the magnification of the VF is involved in your "test". Take the same lens and put it on a D40 and a D300 and you will get different FLs that correspond to 1X..

How do you do that "test" with a camera that only has an LCD (no VF at all)? Or one that has a separate optical (not TTL) VF?.

Charlie DavisNikon 5700, Sony R1, Nikon D300HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/'Experience: Discovering that a claw hammer will bend nails.Epiphany: Discovering that a claw hammer is two tools...'..

Comment #19

David Hughes wrote:.

And could someone please explain about the human eye having about160 FoV? I'm tired of doing it..

Try this test. Cut a hole 24 mm by 36 mm in a piece of card and holdit 50 mm in front of your eye. That's the view you get from a 50 mmlens on a 35 mm film camera and most people will see that it cuts offa lot of the eye's FoV. If it doesn't you've problems, like tunnelvision..

What you've said here makes good sense; the field of view of the eye is very wide..

Still, it seems to be distantly related to the idea of a 50mm lens being chosen as the "standard" lens for 35mm. Suppose you have a print about 6 x 4 inches from an ordinary photo made with the "standard" 50mm lens..

Now, continuing the experiment begun with the piece of card. Looking through the 24 x 36m hole in the card, held at 50mm in front of the eye, take a look at the 6x4 print. Does the print appear larger or smaller than the hole in the card? Of course it depends on the distance to the print, which I've not specified. But supposedly at "normal" viewing distance the print will appear roughly the same size as the hole in the card. That is to say, it will cover the same angle of view..

It's because of this that the perspective from the 50mm lens is regarded as "normal" since the angles of objects within the picture are roughly the same as they were in the original scene..

I suppose another way to do the experiment with the 6 x 4 inch print is to go and stand on the exact spot where the camera was positioned to take the original picture. Now it is possible to compare the angles and field of view directly with the real world..

Regards,Peter..

Comment #20

VidER wrote:.

Hi All..

Coming from P&S background, I am used to measure zoom (Optical orDigital) with X as in 4x, 200x, etc..

But now with DSLRs Lenses are measured with length (70-200mm)..

How can I compare the two type of zooms?.

What is 4x in mm?.

4 can be anything. 4 can be 10-40mm extremely wide angle lens also 4 can be 100-400mm tele lens. It's the longest focal length divided by the shortest focal length..

Edvinas..

Comment #21

Yes you are right, different cameras do have different 1xs..

You can't do that test on a an LCD only camera and I never implied that you could.Jules.

Chuxter wrote:.

Unfortunately, the magnification of the VF is involved in your"test". Take the same lens and put it on a D40 and a D300 and youwill get different FLs that correspond to 1X..

How do you do that "test" with a camera that only has an LCD (no VFat all)? Or one that has a separate optical (not TTL) VF?.

Charlie DavisNikon 5700, Sony R1, Nikon D300HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/'Experience: Discovering that a claw hammer will bend nails.Epiphany: Discovering that a claw hammer is two tools...'.

Why can't you blow bubbles with chewing gum?..

Comment #22

The OPs problem is comparing compact camera lenses with dSLR lenses. My point was that your method of defining what 1X is doesn't help..

A possible revision to that idea might be good. As others have mentioned, we perhaps need to relate everything to a horizontal FOV...38 degrees is equal to 50mm on a 35mm camera. This will work on all cameras and allow comparisons..

When talking about a zoom lens (the OP was interested specifically in comparing zoom ranges), it would be easy and informative to say that a lens' horiz FOV was 15 deg to 74 deg. This would be the same regardless of the actual FLs and the crop factor..

JulesJ wrote:.

Yes you are right, different cameras do have different 1xs.You can't do that test on a an LCD only camera and I never impliedthat you could.Jules.

Chuxter wrote:.

Unfortunately, the magnification of the VF is involved in your"test". Take the same lens and put it on a D40 and a D300 and youwill get different FLs that correspond to 1X..

How do you do that "test" with a camera that only has an LCD (no VFat all)? Or one that has a separate optical (not TTL) VF?.

Charlie DavisNikon 5700, Sony R1, Nikon D300HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/'Experience: Discovering that a claw hammer will bend nails.Epiphany: Discovering that a claw hammer is two tools...'.

Why can't you blow bubbles with chewing gum?.

Charlie DavisNikon 5700, Sony R1, Nikon D300HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/'Experience: Discovering that a claw hammer will bend nails.Epiphany: Discovering that a claw hammer is two tools...'..

Comment #23

Hi,.

It might be nearer the truth to say that 50mm was the normal prime lens they put in the box with the 35mm SLR in film days, then the 35 - 70 zoom replaced it and then the 28 to 90 etc etc..

Many of us can think without much hesitation of normal lenses of 40, 42, 45, 50 and 53 and even 55 mm as primes on 35 mm. And 75 mm on mf and 135mm on tech cameras, although normal is not the word I'd use for a lens for a 4" x 5"..

BTW,trying to trace where is bit about perspective came from is an endless task. It's well engrained but little else, imo. The earliest references I've seen to the 5o mm lens were to the "universal" lens in the 1930's but nothing about perspective or FoV..

Regards, David..

Comment #24

Mm focal length correspond to field of view..

The field of view (or imaging circle) doesn't change with the size of the sensor..., you just get more or less image at the focal plane..

PS.

The focal length as engraved on your lens is at 'focus at infinity', when you focus on an object closer than infinity the effective focal length gets shorter and the imaging circle larger...

Comment #25

We're confusing X's. The typical way it's used on a camera is that the telephoto end is x times the focal length of the wide end..

But, X is used a different way with binoculars and telescopes. There, the view though the instrument is magnified X times what you see with the naked eye..

If you bring viewfinder magnification into it, you're using X the second way, which is not typical for photography...

Comment #26

VidER wrote:.

How can I compare the two type of zooms?.

By using the 35 mm equivalent field of view and doing the math...

Comment #27

IF...33mm is a normal lens FOV....than a 66mm is 2x, 99mm =3x...OK, now here a different viewpoint....That the OP may have meant ???.

A 100-400 zoom has a 4x "ZOOM" factor....BUT the Magnified View compared to a NORMAL lens...IS TOTALY DIFFERANT.....

In a 1.5x crop, a 33mm is a normal lens (46 Degrees FOV).

SO a 100mm lens is a 3x (99mm) Magnification from the 33mm lens.. That is..you are optically 3 times closer to your subject without you moving one foot..

A 400mm lens brings you optically 12 Times closer to your subject without you moving one foot..

ON a 2x Crop...4/3rds....a normal lens is 25mm (1x), than a 100mm (4x from normal), would bring you 4 times closer to your subject without you moving one foot..

To find the Magnification factor...Start from the NORMAL Lens, and divide that number into your longer FL.PLA54..

Comment #28

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