lens x factor

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Keith Butler

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Hi,
I am a newbe and have just bought my first SLR, I am trying to understand the focal length and the x factor, I have a Tamron 70-300 lens so I have an x factor of 4.28 and am trying to get close ups of widlife in my garden, I have seen a Tamron 18-270 lens and would think this would have an x factor of 15, would I get better close ups with this lens or does it just give me a wider focal range. On binoculars the higher the x factor the closer you get in.
 
The higher the number the further the zoom. So your 70-300mm lens is longer and gives more zoom than the 18-270 you mention. As you say, its a wider lens, hence why it seems to give more "x factor"
Dont worry about x factors, its irrelevent really.
 
The x factor as you call it is really a marketing tool used mostly with compact cameras, and is just the difference between the short and long end of the zoom range. With binoculars it relates to how much bigger an image will be compared to normal eyesight, so binoculars rated as 10x will give you an image that is 10 times bigger than the naked eye.

The important part for lenses used on dslr cameras is the actual number, and not how much bigger one is compared to the other. So, with the lenses you mention, the 300mm lens will give you a bigger image than the 270mm, though there won't be much in it as they are very similar in focal length.

For noticeably bigger images, you would need to look at 400mm or even 500mm lenses. Alternatively, there are teleconvertors available that will effectively increase the focal length of your existing lens. The downside is that they reduce the amount of light reaching the sensor, and depending on the lens/camera combination, the autofocus may not work due to the reduction in light.
 
hi keith, welcome to the forums!

also be aware that if you've bought a lower end DLSR (like mine for example) then it might have a cropped APS size sensor.
therefore because of the distance of the lens to the sensor you actually get more range out of your lens
for canon cropped sensors for example you will get 300mmx1.6 as your focal length instead of just 300mm if you have a full frame camera
x zoom is very much a compact generalised marketing gimmick as it's obvious (ish) to everyone
what confuses me a bit is that you get diminishing returns with your lenses. so I have a 400mm length on my camera lens now but it's not that much difference from 300mm that I Had before to be honest. but the difference from 200 to 300 is very noticeable. it's all relative
 
Hi,
Thanks for your help, so is what you are saying, there is only one movable lens that adjusts from say 70mm up to 300mm unlike a telescope which has two lenses front and back which gives the magnification.
 
No not really. Lenses have groups of glass inside. Some are fixed and some move. The moving sections could have 3 or 4 different lenses contained within it.

Its irrelevent anyway really. All you need to know is 18mm is wide angle, and 300mm is telephoto. The lower the number, the wider the view, the higher the number, the further the zoom.
 
DizMatt said:
hi keith, welcome to the forums!

also be aware that if you've bought a lower end DLSR (like mine for example) then it might have a cropped APS size sensor.

therefore because of the distance of the lens to the sensor you actually get more range out of your lens
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I'm sorry to be blunt, but that's complete cobblers. The distance from the lens to the sensor is the same irrespective of the size of the sensor. If that were not the case, a lens that physically fits both formats wouldn't focus properly on one of them.

A 200mm lens produces exactly the same image no matter what it is attached to. The reason a crop camera appears to be using a longer lens is because the smaller sensor captures a smaller part of the image. Imagine taking a 6x4 print and cutting away an inch all the way round, leaving you with a 4x2 print. If this print is then resized back to the original size of 6x4, it will not contain as much detail as the original print, and what you are left with will appear as if it was taken with a bigger lens. This is what a crop sensor does. What actually changes is the field of view that is captured by the camera, so that the crop camera image appears to have been taken by a lens of longer focal length, equivalent to the lens x the crop factor of the camera. In Canon's case 1.6 for the beginner type cameras or 1.3 for the 1 series cameras.
 
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Hi,
Thank you for your reply, as I said I am a newbe so be easy with me. I have a Nikon d3100 and it has a crop factor of 1.5, and has 14 meg pixels, when I take a photo with my 300mm lens and the photo is cropped I have read that the camera itself changes that image into a full frame picture, so does the final picture still have 14 meg pixels. Also with this crop factor what size would a desent wide angle lens be.
 
No your camera doesnt change your image into a full frame picture, A dslr with a crop sensor just gives a different telephoto range, so your photo at 300mm on the camera is actualy 450mm, the amount of megapixels makes no difference.
 
Hotshots said:
No your camera doesnt change your image into a full frame picture, A dslr with a crop sensor just gives a different telephoto range, so your photo at 300mm on the camera is actualy 450mm, the amount of megapixels makes no difference.
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A 300mm lens is a 300 mm lens regardless of crop factor or anything else it never becomes a 450 mm lens. The field of view on a 1.5 x crop camera is equivalent to 450 mm on a 35mm (full frame camera)
 
boyfalldown said:
A 300mm lens is a 300 mm lens regardless of crop factor or anything else it never becomes a 450 mm lens. The field of view on a 1.5 x crop camera is equivalent to 450 mm on a 35mm (full frame camera)
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Thats exactly what i mean i think you havent understood my reply fully.
 
Scarecrow said:
I'm sorry to be blunt, but that's complete cobblers. The distance from the lens to the sensor is the same irrespective of the size of the sensor. If that were not the case, a lens that physically fits both formats wouldn't focus properly on one of them.

A 200mm lens produces exactly the same image no matter what it is attached to. The reason a crop camera appears to be using a longer lens is because the smaller sensor captures a smaller part of the image. Imagine taking a 6x4 print and cutting away an inch all the way round, leaving you with a 4x2 print. If this print is then resized back to the original size of 6x4, it will not contain as much detail as the original print, and what you are left with will appear as if it was taken with a bigger lens. This is what a crop sensor does. What actually changes is the field of view that is captured by the camera, so that the crop camera image appears to have been taken by a lens of longer focal length, equivalent to the lens x the crop factor of the camera. In Canon's case 1.6 for the beginner type cameras or 1.3 for the 1 series cameras.
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I stand/sit corrected!
 
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Hi,
Dizmat you seem to be the only person who has answered my questions and explained to me the answere, I dont think anyone knows all the answeres we are all learning in one way or another. Is the quality of picture that a croped sensor produces a lower quality because the picture gets enlarged to match a full frame and then the camera software plugs the gaps left from the enlargment.
 
Not sure what your getting at but basicaly a FF sensor can capture more information because it is a bigger sensor and therefore captures more light, Hence the quality is better than its crop sensor's equivilant.

And yes i do understand what the difference is between FF camera and a crop sensor camera, Dizmatt put it in easier way to understand.
 
Keith Butler said:
Hi,
Dizmat you seem to be the only person who has answered my questions and explained to me the answere, I dont think anyone knows all the answeres we are all learning in one way or another. Is the quality of picture that a croped sensor produces a lower quality because the picture gets enlarged to match a full frame and then the camera software plugs the gaps left from the enlargment.
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It doesn't enlarge anything. It is what it is.
A full frame camera will produce a bigger image than a crop. There is no filling in gaps or enlargements.

And I answered your question in my first post, thanks for the acknowledgement.
 
Keith Butler said:
Hi,
Dizmat you seem to be the only person who has answered my questions and explained to me the answere, I dont think anyone knows all the answeres we are all learning in one way or another. Is the quality of picture that a croped sensor produces a lower quality because the picture gets enlarged to match a full frame and then the camera software plugs the gaps left from the enlargment.
Click to expand...

Here's another way of thinking about cropped vs full frame.

Take a full frame camera and, if you could, put masking tape around the top/bottom/sides to cover over half the sensor area. The bit in the middle now gives you a crop sensor camera, and it would be 1.4x crop factor.

In cropping off the outsides of the image area, you have obviously cropped the field of view, so to restore that you need to reduce the focal length and use a lens that produces a smaller image, to the tune of whatever the crop factor is - 1.5x Nikon/Sony, 1.6x Canon, ie both a bit smaller than half the sensor image area of full frame.

The main benefit of full frame is image quality. The larger sensor collects more light, so noise is lower, dynamic range higher, colours are cleaner. The other upside is because the lenses don't have to work so hard to deliver a given standard of sharpness, contrast is better and images have more pop. All in theory, all things being equal and all that, but it is pretty much born out in practise.

The other significant difference, though in practise it's not huge, is because the magnification is changed to produce a final image/print of a certain size, depth of field changes. Full frame gives less depth of field at the same f/number, from the same viewpoint, image framed the same (ie focal length adjusted). The difference is a bit over one stop, calculated as f/number x crop factor.
 
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This is an object lesson in why people should stop pushing 'full frame' and crop factors at newbies.

The OP had nothing whatsoever about crops and was a misunderstood question about zoom lenses. It was answered simply, but those answers are now lost in a mire of confusion that is neither necessary or helpful.

The 35mm full frame sensor size isn't the standard by which all cameras must be judged. Over the hundred and eighty years we've been taking photo's there have been many common standards - why digital photographers are drawn towards 36x24 is just ridiculous to me.

In the later days of film the kind of photographers drawn to FF cameras were shooting medium format. But people weren't looking at their 35mm cameras and calling their 50mm lens an 80mm equivalent:lol:. Likewise someone who's bought a crop DSLR doesn't need to know that his 18-55 is a 28-80 equivalent lens. He only needs to know its a standard zoom and why he might want a wider or longer lens or a closer focussing lens.

Because the crop factor makes for some easy maths people can't wait to trot out their 'understanding', most of which is actually less than a real understanding BTW. There's more to focal length than field of view, and theres more to sensor size than crop factors. But those maths aren't simple.:geek:
</soapbox>
 
It appears everyone has missed the OP's question - to me it appears as the questions is: will an 18-270 lens get me closer than a 70-300 (because expressed as X zoom it is higher).

The simple answer is No, the larger the higher number - the closer you get (e.g, 300 is bigger than 270, so will get you closer! a 600mm lens is closer still).

Hope that kind of answers the actual question.
 
stew1982 said:
It appears everyone has missed the OP's question - to me it appears as the questions is: will an 18-270 lens get me closer than a 70-300 (because expressed as X zoom it is higher).

The simple answer is No, the larger the higher number - the closer you get (e.g, 300 is bigger than 270, so will get you closer! a 600mm lens is closer still).

Hope that kind of answers the actual question.
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Nope - first two answers had it...
 
Phil V said:
Nope - first two answers had it...
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Phil, if you read the OP's further responses, especially post #13, you will see that the question is (it turns out!) about crop factors, and not zoom ratios.

And though I know where you're coming from with your other comments, you're just going to have to put up with crop factor questions and confusion because that's what we have to deal with.

And there are more different crop factors appearing all the time it seems, not less, and they all relate to full frame as the reference standard. This makes sense because for about 40 years it was the overwhelmingly dominant format, used by enthusiasts, professionals and rank amateurs alike. We need some kind of reference, and it's especially important as a comparator when we now use the same lenses on different format cameras.

Edit: I know you know this, I just don't know why it bothers you ;)
 
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HoppyUK said:
We need some kind of reference, and it's especially important as a comparator when we now use the same lenses on different format cameras.
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Most of us don't use the same lenses on different format cameras - we use them on one format only therefore there is no need for a comparator - and those that do use the same lens on different format cameras will undoubtedly have enough understanding not to have to ask the questions.

HoppyUK said:
you're just going to have to put up with crop factor questions and confusion because that's what we have to deal with
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It is the perennial reference to crop factors where it is irrelevant that causes the crop factor questions and confusion and we only have to deal with it because people make those unnecessary, irrelevant and sometimes incorrect references.

HoppyUK said:
And there are more different crop factors appearing all the time it seems, not less, and they all relate to full frame as the reference standard. This makes sense because for about 40 years it was the overwhelmingly dominant format
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But full-frame is not the dominant format in digital photography - it is not different crop factors that are appearing but different sized sensors; different to full-frame and different to each other - times have moved on - for manufacturers and enthusiasts/professionals/amateurs alike to keep referring to FF-equivalent crop-factors when talking about lenses as though it actually matters is an anachronism - a photographer needs to understand how wide or not a lens is on a particular camera - to make reference to a different camera that the photographer doesn't own, has never owned and might not ever own (and then go on to say that a 300mm lens is really/becomes a 480mm on a particular camera) is what causes the confusion.

EDIT: Despite what I've said above, I do appreciate that sometimes it is useful to be able to do a quick calculation to compare how wide (or long) a particular focal length will be on a particular camera but I think that this is a 'technique' that is best used where it is understood as a tool for those in the know and not as a 'camera fact' that needs to be trotted out to explain something to a novice. Unfortunately, explanations need to be trotted out to try to overcome the misconceptions and misinformation caused by crop-factor fixation.
 
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weybourne said:
Most of us don't use the same lenses on different format cameras - we use them on one format only therefore there is no need for a comparator - and those that do use the same lens on different format cameras will undoubtedly have enough understanding not to have to ask the questions.
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That's not the point. The point is that you (ie others) can use the same lens on different cameras, and depending on which brand/model you have, it makes a big difference. Manufacturers refer to it, sales people refer to it, magazines and reviews refer to it, and it's here to stay. Try explaining an EF-S or DX lens without refering to it.

It is the perennial reference to crop factors where it is irrelevant that causes the crop factor questions and confusion and we only have to deal with it because people make those unnecessary, irrelevant and sometimes incorrect references.
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See above. You might think it's irrelvant, and often it is, but the question comes up all the time. It's one of the most frequent topics, along with depth of field and exposure settings and modes.

But full-frame is not the dominant format in digital photography - it is not different crop factors that are appearing but different sized sensors; different to full-frame and different to each other - times have moved on - for manufacturers and enthusiasts/professionals/amateurs alike to keep referring to FF-equivalent crop-factors when talking about lenses as though it actually matters is an anachronism - a photographer needs to understand how wide or not a lens is on a particular camera - to make reference to a different camera that the photographer doesn't own, has never owned and might not ever own (and then go on to say that a 300mm lens is really/becomes a 480mm on a particular camera) is what causes the confusion.
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You're quite right, full frame is not the dominant format. But 35mm film was, overwhelmingly and for a very long time, and that's where it all started - when people were moving over from film to DSLRs that all had crop format sensors back then. A conversion factor was needed, and it's stuck because it's still a very handy reference and is still used a lot, whether we like it or not.

There is some logic to using field/angle of view instead of focal length, but that would cause even more confusion because it changes according to format. And it's always quoted across the diagonal, which doesn't help. And nobody knows what they are off the top of their head. We talk about focal length, and at least that's an absolute.
 
Hi Richard - I think you might have posted before my edit appeared - I think we're coming from the same place but with different emphasis ;)
 
weybourne said:
Hi Richard - I think you might have posted before my edit appeared - I think we're coming from the same place but with different emphasis ;)
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Yes, but I did see it after I posted.

We're all in the same place, just some folks don't seem to like it much. But the fact remains that we have various formats and newcomers get confused about why the same lens behaves differently on each. The crop factor was invented to address that, using full frame as the basic yardstick.

I think it's a pretty good solution to quite a complex problem (crop factor works for adjusting the relative DoF too) but we're stuck with it either way.
 
stew1982 said:
It appears everyone has missed the OP's question - to me it appears as the questions is: will an 18-270 lens get me closer than a 70-300 (because expressed as X zoom it is higher).

The simple answer is No, the larger the higher number - the closer you get (e.g, 300 is bigger than 270, so will get you closer! a 600mm lens is closer still).

Hope that kind of answers the actual question.
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Yeah cos that's not what I said immediately after the ops post is it?
 
TCR4x4 said:
The higher the number the further the zoom. So your 70-300mm lens is longer and gives more zoom than the 18-270 you mention. As you say, its a wider lens, hence why it seems to give more "x factor"
Dont worry about x factors, its irrelevent really.
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Just for another example, I have a 15-85mm lens and a 100-400mm lens, the latter has less x factor than the former but the former would be practically useless for wildlife.

Zoom gives you flexibility but ultimately you need a long lens for wildlife.
 
HoppyUK said:
Phil, if you read the OP's further responses, especially post #13, you will see that the question is (it turns out!) about crop factors, and not zoom ratios.

snip

Edit: I know you know this, I just don't know why it bothers you ;)
Click to expand...
You mean post 13 here...

Keith Butler said:
Hi,
Dizmat you seem to be the only person who has answered my questions and explained to me the answere, I dont think anyone knows all the answeres we are all learning in one way or another. Is the quality of picture that a croped sensor produces a lower quality because the picture gets enlarged to match a full frame and then the camera software plugs the gaps left from the enlargment.
Click to expand...
No, what happened here is that he got confused because people started the crop discussion.. Not picking on Hotshots, there were others.

Hotshots said:
No your camera doesnt change your image into a full frame picture, A dslr with a crop sensor just gives a different telephoto range, so your photo at 300mm on the camera is actualy 450mm, the amount of megapixels makes no difference.
Click to expand...
But the OP was definitely..


lens x factor
Hi,
I am a newbe and have just bought my first SLR, I am trying to understand the focal length and the x factor, I have a Tamron 70-300 lens so I have an x factor of 4.28 and am trying to get close ups of widlife in my garden, I have seen a Tamron 18-270 lens and would think this would have an x factor of 15, would I get better close ups with this lens or does it just give me a wider focal range. On binoculars the higher the x factor the closer you get in.

about the multiplication between the short and long end of a zoom and how it was confusing him (comparison to binoculars a big clue) The crop factor thing just came out of the blue to muddy the waters.

And my issue with the crop debate and newbies is that it's simply something they don't need to know until they've started thinking about a FF camera after owning a crop body. 35mm may have been the dominant format for years but it isn't now and it's ridiculous to keep banging on about it when people are having enough trouble understanding things that actually make a difference to them. What a telephoto lens does, what's the difference between a tele and a macro lens etc.

A bit like a new driver trying to get to grips with his Corsa and people advising him about Turbo lag should he move up to a Porsche.
 
can I just wade in and say that I thought that FF cameras gave a clearer picture because of pixel density and electron migration. although you would need better quality glass edge to edge due to the sensor size
/just trying to recover some geek points here :p

so short answer is that 300mm is greater than 270mm
it's not the difference or multiple between the short end and the long end of the zoom range of the lens.
18-20 ish is good for wide angle and landscapes
50-80mm is good for nice portraits
250-300mm is good for wildlife (unless you're VERY close to a man eating tiger at which point some toilet paper is handier!)
 
DizMatt said:
can I just wade in and say that I thought that FF cameras gave a clearer picture because of pixel density and electron migration. although you would need better quality glass edge to edge due to the sensor size
/just trying to recover some geek points here :p
Click to expand...

Nice try, but no. See post #16.

so short answer is that 300mm is greater than 270mm
it's not the difference or multiple between the short end and the long end of the zoom range of the lens.
18-20 ish is good for wide angle and landscapes
50-80mm is good for nice portraits
250-300mm is good for wildlife (unless you're VERY close to a man eating tiger at which point some toilet paper is handier!)
Click to expand...

This needs to be qualified by stating the format. 18-20mm is pretty wide on full frame, but not really on a cropper. 50-80 is good for portraits on a cropper, but a bit short on full frame, and for wildlife on full frame you really need to be looking at 400mm-plus. See what I mean? And the difference is expressed by the crop factor, which is the commonly used measure of equivalence (sorry Phil :D).
 
Hi everybody,
I appreciate all the advice and the comments and understand now about the length of a lens and the crop factor of a sensor, one last question I have to complete the X factor which is the magnification, does the pixel count matter on the magnification question? I have an example, the daily mirror had a photograph taken of a crowd scene at the recent royal wedding, this picture was taken with a billion pixel digital camera and if you went on the internet you could zoom into the 1000 people crowd and if you spotted yourself you could capture and print the image of yourself.
 
It wasnt taken with a billion pixel camera, it was several hundred photos taken on a normal camera and stiched together to make a huge image.
 
Hi,
When I was listening to a very famous photographer he said it was probably taken with a billion pixel camera that's why I said it. So the question was does the pixel count make a difference?
 
Keith Butler said:
Hi,
When I was listening to a very famous photographer he said it was probably taken with a billion pixel camera that's why I said it. So the question was does the pixel count make a difference?
Click to expand...

Not a billion pixel camera (there is no such thing) but as explained above. For this kind of detail you need both lots of pixels and a lens capable of resolving said detail - the two go hand in hand.

BTW, this has nothing to do with the OP, nor any of the subsequent digressions!
 
Keith Butler said:
Hi,
When I was listening to a very famous photographer he said it was probably taken with a billion pixel camera that's why I said it. So the question was does the pixel count make a difference?
Click to expand...

Keith
(another not the x factor)
As the others have said, there's no such camera, the picture is made up of 220 seperate images according to the reports at the time. This would have either been 1 camera taking 220 images, or more likely a bank of cameras (though not 220). They would have used a telephoto lens, if you can imagine a grid of 220 overlaid over that image you can then imagine how that then allows the 'zoom' effect when you click the image. If you look at it close enough you'll find the areas where the merging of images hasn't been perfect and has caused distortion (slight multiple exposures of the same person).

Again though, the 'x' factor is something used in marketing of point and shoot cameras. It really is no use for DSLR's, has nothing to do with optical quality or resolution and isn't related to the x in Binocular specifications. It's hard but you should really just forget about it, as you've got enough useful information to take on board without being distracted by a meaningless piece of info.
 
Hi,
I thank every one for your kind replies and for all the advice, as you can imagine I have a lot to learn and maybe I will be competent enough to take a photo soon.
Many thanks
 
More mm = closer view on subject.

The x factor is just the number of times the shortest length will divide into the longest length. So the bigger range you have on a zoom lens the higher the 'x factor' is going to be. But it sells compacts...
 
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