It would be approximately a 350mm lens in 35mm format, or 225mm on a 1.5 crop factor DSLR..

JohnPentax *ist-D, K100D, Fuji F20/31fd, Oly Stylushttp://www.pbase.com/jglover..

But x7 on binoculars is a measure of the magnification..

You should be looking at the FoV (Field of View) of the x7's you are talking about and trying to match it on the camera's zoom etc. And, of course, the aspect ratio then comes into it because the FoV is measured across the diagonal but cameras give you a wider FoV for the horizontal than vertical and binoculars give a circular FoV..

To add to the confusion, some makers of binoculars quote things like 140 m at 1,000 m instead of an angle in degrees but a little bit of schoolboy maths will sort that out..

And, of course, looking through an optical viewfinder on a camera will change it a bit but I assume you want to fill the frame vertically with what you get from the binoculars, in which case you'll need to do a few more sums to get the FoV vertically for whatever the aspect ratio is..

Regards, David...

Boy, good answers. All I am trying to do is match the sizing or closeness of the bird. Based on the answers so far 350mm is not close enough so I would need about 100mm more. Fov is of course getting smaller as this increases. I think I understood it but just wanted confirmation..

ThanksJames..

If 7X binoculars have enough magnification then a 350mm equivalent will as well. The X is generally based on 50mm being 1X..

I have seen various discussions about what actually is 1X in a lens as it relates to the eye. Most say it involves the diagonal of the 35mm frame, which comes out a bit less than 50mm. The only lens I ever had that seemed to be exactly 1:1 when looking at the view with one eye and through the viewfinder with the other was a 57mm on my old SRT101. I dont really know the right answer but 7X binoculars should have about the same magnification as a 350mm lens..

Field of view decreases with power on a camera lens. So to go from 350 to 450mm will decrease your FOV..

That doesnt necessarily apply directly apply to binoculars though. If you look through a cheap pair of non-prismatic binoculars or opera glasses you probably get the same field of view per power as you do with a camera lens. Same for telescopes. But prismatic binoculars do some magic with the optics that gives a wider FOV for a given power. Generally the FOV decreases with power, but you can get 7X binoculars with varying FOVs. It is evidently dependent on the eyepiece.

In short you will find the 7X is probably close to the magnification of a 350mm lens. But dont expect the 350mm lens to have the same FOV as your binoculars..

Look at the varying angle of view for 7X binoculars on this page: http://www.monkoptics.co.uk/general.html Camera lenses dont work like that at least I am not familiar with any that do...

Slipe wrote:.

If 7X binoculars have enough magnification then a 350mm equivalentwill as well. The X is generally based on 50mm being 1X..

I have seen various discussions about what actually is 1X in a lensas it relates to the eye. Most say it involves the diagonal of the35mm frame, which comes out a bit less than 50mm. The only lens Iever had that seemed to be exactly 1:1 when looking at the view withone eye and through the viewfinder with the other was a 57mm on myold SRT101. I dont really know the right answer but 7X binocularsshould have about the same magnification as a 350mm lens..

You've lost me. Human vision as a base for magnification has nothing to do with FOV. The human eye resolves a certain amount of detail, magnifying that ability to resolve detail by a factor of seven is the binoculars in question. Whatever the cropping factor of the sensor, has no effect on the actual magnification (i.e, resolving power). Cropping an image results only in "apparent" magnification..

If he wants to be seven times closer to the bird, he needs seven times magnification, not apparent magnifaction..

Dave.

Field of view decreases with power on a camera lens. So to go from350 to 450mm will decrease your FOV..

That doesnt necessarily apply directly apply to binoculars though.If you look through a cheap pair of non-prismatic binoculars or operaglasses you probably get the same field of view per power as you dowith a camera lens. Same for telescopes. But prismatic binocularsdo some magic with the optics that gives a wider FOV for a givenpower. Generally the FOV decreases with power, but you can get 7Xbinoculars with varying FOVs. It is evidently dependent on theeyepiece. To get a wider angle of view you decrease the eye relief in other words you have to get closer to the eyepiece to see theentire field of view.

But dont expect the350mm lens to have the same FOV as your binoculars..

Look at the varying angle of view for 7X binoculars on this page:http://www.monkoptics.co.uk/general.html Camera lenses dont worklike that at least I am not familiar with any that do...

Jbarber wrote:.

Boy, good answers. All I am trying to do is match the sizing orcloseness of the bird. Based on the answers so far 350mm is not closeenough so I would need about 100mm more. Fov is of course gettingsmaller as this increases. I think I understood it but just wantedconfirmation..

ThanksJames.

Which camera?.

As John Glover mentions, watch the crop factor of the sensor. The 50mm is based on "full frame" 35mm film. 1x for 645 medium format film is 75-80mm. For an APS-C digital sensor (very common in dSLRs), it's about 35mm. So, in the case of a digital camera with an APS sensor, 350mm would be roughly 10X...

Tatanka wrote:.

Jbarber wrote:.

Boy, good answers. All I am trying to do is match the sizing orcloseness of the bird. Based on the answers so far 350mm is not closeenough so I would need about 100mm more. Fov is of course gettingsmaller as this increases. I think I understood it but just wantedconfirmation..

ThanksJames.

Which camera?.

As John Glover mentions, watch the crop factor of the sensor. The50mm is based on "full frame" 35mm film. 1x for 645 medium formatfilm is 75-80mm. For an APS-C digital sensor (very common in dSLRs),it's about 35mm. So, in the case of a digital camera with an APSsensor, 350mm would be roughly 10X..

The cropping factor produces "apparent" magnification, not real resolving power. If you want to resolve the detail that a seven power lens can give you, then you need a seven power lens..

You can easily prove this for yourself by putting a 50mm lens on your 1.5 camera and look thorugh the viewfinder, and then at the scene - There will be no difference in how far your subject appears to be..

These remarks of mine are only about dSLR's, digicams use miniature lenses that do in fact magnify, resolve objects..

DaveDave..

I have no camera yet. I am still considering what that will be. I really do want a zoom and I was trying to understand what size zoom would match 7x binoculars just for a set point for me to go from. I am not thinking about depth of field just pure sizing. I now understand that my thought that 50mm was 1 to 1 human vision is correct and that 7X would be 350mm. I understand also the focal multiplier now for small sensors cameras vs 35 mm.



James..

Jbarber wrote:.

I have no camera yet. I am still considering what that will be. Ireally do want a zoom and I was trying to understand what size zoomwould match 7x binoculars just for a set point for me to go from. Iam not thinking about depth of field just pure sizing. I nowunderstand that my thought that 50mm was 1 to 1 human vision iscorrect and that 7X would be 350mm. I understand also the focal.

I think that without getting into a lot of deep thought over what constitutes normal magnification and resolving power and FOV, etc......all you need to do is get you a camera that have the equivalent of about a 300mm focal length on 35mm terms, and you will be happy. So, if you are looking at a compact digital or a prosumer camera, just get one that has somewhere around 300mm equivalent as the top end of the zoom.....if a DSLR, then look to get the lens (typically about 18-55mm zoom) and add on a a 50-200mm zoom or even better, a 70-300mm and you will have everything you want covered..

JohnPentax *ist-D, K100D, Fuji F20/31fd, Oly Stylushttp://www.pbase.com/jglover..

You mentioned 7x and matching the sizing or closeness of a bird- Not knowing what photographic situation your biggest concern is (nature photography?), what you are looking to do with the end results (ie screen images or prints?) and what level of camera you are looking to buy (Prosumer or DSLR?) it's a little hard to give a good answer..

Just from my experience as an amateur-.

- Any of the current crop of prosumer "superzooms" will give you better than the binocular 7x magnification you are talking about (although keep in mind that the "x" factor refers to the zoom range, and most if not all start from a wider perspective)..

- If you plan on taking pics at the long end of the zoom a lot without using a tripod IS almost a must (this will help camera shake, but not subject movement)..

- If you plan on taking mostly low light photo's you will probably want to go with a DSLR and at least one lens with a 300mm or greater focal length (ie 450mm equivalent for 35mm film), every prosumer I've used has done a good job in bright light, but in lower light image quality suffers tremendously, and regardless of what ISO settings they have most are very noisy above 200 ISO where most DSLR's still perform well at 800 ISO..

I don't know if any of this helps, but please feel free to check out my on-line gallery (link below), as with many other photo sites you can view the EXIF data including focal lengths the shots were taken at which may also help to give you some clarification on the subject. Milan.

Nikon D50w/ Tamron 28-75 f2.8, Nikon 28-200 f3.5-5.6 and Sigma 135-400 f4.5-5.6Cannon S2isOlympus Stylus 720swGallery: http://etherialone.zenfolio.com/..

Chato wrote:.

Slipe wrote:.

If 7X binoculars have enough magnification then a 350mm equivalentwill as well. The X is generally based on 50mm being 1X..

I have seen various discussions about what actually is 1X in a lensas it relates to the eye. Most say it involves the diagonal of the35mm frame, which comes out a bit less than 50mm. The only lens Iever had that seemed to be exactly 1:1 when looking at the view withone eye and through the viewfinder with the other was a 57mm on myold SRT101. I dont really know the right answer but 7X binocularsshould have about the same magnification as a 350mm lens..

You've lost me. Human vision as a base for magnification has nothingto do with FOV. The human eye resolves a certain amount of detail,magnifying that ability to resolve detail by a factor of seven is thebinoculars in question. Whatever the cropping factor of the sensor,has no effect on the actual magnification (i.e, resolving power).Cropping an image results only in "apparent" magnification..

Are you sure you are responding to the right quote? I said nothing about crop factor or FOV. That first part is in answer to the title of the thread and the original question..

Hold a DSLR (or SLR) up to your eye with the long side up (portrait) so you can see the same scene with the other eye. Say you are looking through the camera with your right eye. With a 100mm equivalent lens on the camera your eyes cant resolve the image into a single image because your right eye is seeing a magnified image. There is a focal length at which something like a pole will be perfectly matched between the two eyes. That was the case with the 57mm normal lens on my SRT101. My Nikon F came with a 50mm normal lens and the right eye saw a very slightly smaller image than the left eye.



If he wants to be seven times closer to the bird, he needs seventimes magnification, not apparent magnifaction..

Seven times what? He asked for a lens relation to the magnification of 7X binoculars. Im not sure all binocular makers are exactly to the 1X = 50mm standard, but a 350mm lens is pretty close to the magnification of 7X binoculars..

It was David Hughes who equated FOV to magnification. He said You should be looking at the FoV (Field of View) of the x7's you are talking about and trying to match it on the camera's zoom etc. If you match the FOV of a pair of wide angle 7X binoculars with the camera zoom and then match the FOV of a narrow field of view 7X binoculars you will get completely different magnifications on the lens. Both binoculars are 7X magnification, so FOV doesnt relate directly to magnification. The rest of my post was a response to that..

Field of view decreases with power on a camera lens. So to go from350 to 450mm will decrease your FOV..

That doesnt necessarily apply directly apply to binoculars though.If you look through a cheap pair of non-prismatic binoculars or operaglasses you probably get the same field of view per power as you dowith a camera lens. Same for telescopes. But prismatic binocularsdo some magic with the optics that gives a wider FOV for a givenpower. Generally the FOV decreases with power, but you can get 7Xbinoculars with varying FOVs. It is evidently dependent on theeyepiece. To get a wider angle of view you decrease the eye relief in other words you have to get closer to the eyepiece to see theentire field of view.

But dont expect the350mm lens to have the same FOV as your binoculars..

Look at the varying angle of view for 7X binoculars on this page:http://www.monkoptics.co.uk/general.html Camera lenses dont worklike that at least I am not familiar with any that do...

Slipe wrote:.

If 7X binoculars have enough magnification then a 350mm equivalentwill as well. The X is generally based on 50mm being 1X..

I have seen various discussions about what actually is 1X in a lensas it relates to the eye. Most say it involves the diagonal of the35mm frame, which comes out a bit less than 50mm. The only lens Iever had that seemed to be exactly 1:1 when looking at the view withone eye and through the viewfinder with the other was a 57mm on myold SRT101. I dont really know the right answer but 7X binocularsshould have about the same magnification as a 350mm lens..

Field of view decreases with power on a camera lens. So to go from350 to 450mm will decrease your FOV..

That doesnt necessarily apply directly apply to binoculars though.If you look through a cheap pair of non-prismatic binoculars or operaglasses you probably get the same field of view per power as you dowith a camera lens. Same for telescopes. But prismatic binocularsdo some magic with the optics that gives a wider FOV for a givenpower. Generally the FOV decreases with power, but you can get 7Xbinoculars with varying FOVs. It is evidently dependent on theeyepiece. To get a wider angle of view you decrease the eye relief in other words you have to get closer to the eyepiece to see theentire field of view.

But dont expect the350mm lens to have the same FOV as your binoculars..

Look at the varying angle of view for 7X binoculars on this page:http://www.monkoptics.co.uk/general.html Camera lenses dont worklike that at least I am not familiar with any that do..

I'm a bit puzzled, maybe because I'm unfamiliar with binoculars. But usually the "X" designation is based on longest focal length divided by shortest focal length for cameras. So a 35-350mm lens would be 10x..

But maybe binoculars are different...

Slipe wrote:.

It was David Hughes who equated FOV to magnification. He said Youshould be looking at the FoV (Field of View) of the x7's you aretalking about and trying to match it on the camera's zoom etc. Ifyou match the FOV of a pair of wide angle 7X binoculars with thecamera zoom and then match the FOV of a narrow field of view 7Xbinoculars you will get completely different magnifications on thelens. Both binoculars are 7X magnification, so FOV doesnt relatedirectly to magnification..

I said "to the FoV of the binoculars you are talking about... " precisely to cover the fact that there are no such things as a standard x7 and so the FoV varies. B&L and Pentax both made/make a wide field of view instrument and other make more conventional ones..

Regards, David..

You can see the effect of using a lens by making a simple frame and holding it in front of you at the focal length. This was easy with 35 mm film as all you needed was an empty plastic slide frame and then you wave it about in front of you and it frames what you'll _capture_ on the film. Then you enlarge the film from about 1" x 1" to 8" x 10" and the aspect ratio has changed and the maths gets tedious..

Dare I suggest that you look at the camera you are thinking about and find out the size of the CCD? Then make a frame and play with it at the _real_ focal lengths of the lens....

For example, a "FourThirds" CCD is about 18mm x 13 mm. So cut a hole that size in a bit of card and hold it in front of your eye. What you see through the hole will be what the camera sees when the focal length and the distance from your eye are the same..

Easy, isn't it?.

Regards, David..

I'll repeat the quote:.

You should be looking at the FoV (Field of View) of the x7's you aretalking about and trying to match it on the camera's zoom etc..

If that isn't what you meant to say you might go back and edit the post. What you said is that he should try to match the FOV on the camera zoom. That will not give him the same power. He is looking for the same power as his 7X binoculars. In most cases matching the FOV of his binoculars will give him a lower power lens...

I have been researching cameras heavily, trying to decide what I really what to do with it and the answer is everything. Through this forum, camera manuals and actual holding and touching: I have decided to buy a point and shoot to start. This will likely be the Canon S5. At this point I do not know whether this will be a hobby that will take or will die after a few months. I am retired so I have the time to do it but will I? The Canon will give me quite a bit of the range to try out and after a year if I am still hot on photograpy then I probably will buy a dslr. I actually do now understand what a small sensor or large sensor will do and I have accepted the conditions.



James..

Slipe wrote:.

Chato wrote:.

Slipe wrote:.

If 7X binoculars have enough magnification then a 350mm equivalentwill as well. The X is generally based on 50mm being 1X..

I have seen various discussions about what actually is 1X in a lensas it relates to the eye. Most say it involves the diagonal of the35mm frame, which comes out a bit less than 50mm. The only lens Iever had that seemed to be exactly 1:1 when looking at the view withone eye and through the viewfinder with the other was a 57mm on myold SRT101. I dont really know the right answer but 7X binocularsshould have about the same magnification as a 350mm lens..

You've lost me. Human vision as a base for magnification has nothingto do with FOV. The human eye resolves a certain amount of detail,magnifying that ability to resolve detail by a factor of seven is thebinoculars in question. Whatever the cropping factor of the sensor,has no effect on the actual magnification (i.e, resolving power).Cropping an image results only in "apparent" magnification..

Are you sure you are responding to the right quote? I said nothingabout crop factor or FOV. That first part is in answer to the titleof the thread and the original question..

You're RIGHT! - My bad. .

Hold a DSLR (or SLR) up to your eye with the long side up (portrait)so you can see the same scene with the other eye. Say you arelooking through the camera with your right eye. With a 100mmequivalent lens on the camera your eyes cant resolve the image intoa single image because your right eye is seeing a magnified image.There is a focal length at which something like a pole will beperfectly matched between the two eyes. That was the case with the57mm normal lens on my SRT101. My Nikon F came with a 50mm normallens and the right eye saw a very slightly smaller image than theleft eye. I concluded that for my eyes 57mm was 1:1 magnification..

If he wants to be seven times closer to the bird, he needs seventimes magnification, not apparent magnifaction..

Seven times what? He asked for a lens relation to the magnificationof 7X binoculars. Im not sure all binocular makers are exactly tothe 1X = 50mm standard, but a 350mm lens is pretty close to themagnification of 7X binoculars..

They match it more or less because 55mm is supposed to reflect the human eye. We shorten that to 50mm for convenience. And of course the human eye is an "average" of human eyes..

It was David Hughes who equated FOV to magnification. He said Youshould be looking at the FoV (Field of View) of the x7's you aretalking about and trying to match it on the camera's zoom etc. Ifyou match the FOV of a pair of wide angle 7X binoculars with thecamera zoom and then match the FOV of a narrow field of view 7Xbinoculars you will get completely different magnifications on thelens. Both binoculars are 7X magnification, so FOV doesnt relatedirectly to magnification. The rest of my post was a response tothat..

Field of view decreases with power on a camera lens. So to go from350 to 450mm will decrease your FOV..

That doesnt necessarily apply directly apply to binoculars though.If you look through a cheap pair of non-prismatic binoculars or operaglasses you probably get the same field of view per power as you dowith a camera lens. Same for telescopes. But prismatic binocularsdo some magic with the optics that gives a wider FOV for a givenpower. Generally the FOV decreases with power, but you can get 7Xbinoculars with varying FOVs. It is evidently dependent on theeyepiece. To get a wider angle of view you decrease the eye relief in other words you have to get closer to the eyepiece to see theentire field of view.

But dont expect the350mm lens to have the same FOV as your binoculars..

Look at the varying angle of view for 7X binoculars on this page:http://www.monkoptics.co.uk/general.html Camera lenses dont worklike that at least I am not familiar with any that do..

Dave..

It was a vague question and I had to turn it into something solid. Binoculars magnify by comparison with the unaided human eye. You'll see something seven times larger with x7's. So I thought that pointing out that a FoV for the lens should equall (more or less) the FoV of the binoculars would answer the question..

Once the picture is taken he might print it on 4x6 or 32x24 - which blows any talk of magnfication out of the water..

OTOH you could say that a 50 mm lens on 35 mm film at 24 mm x 36 mm and a 350 mm ditto is a 50 mm lens x7. And magnifies the image seven times..

He has had both answers and can make his own choice. I'll wish him luck in this new venue..

Regards, David..

David Hughes wrote:.

It was a vague question and I had to turn it into something solid.Binoculars magnify by comparison with the unaided human eye. You'llsee something seven times larger with x7's. So I thought thatpointing out that a FoV for the lens should equall (more or less) theFoV of the binoculars would answer the question..

Once the picture is taken he might print it on 4x6 or 32x24 - whichblows any talk of magnfication out of the water..

OTOH you could say that a 50 mm lens on 35 mm film at 24 mm x 36 mmand a 350 mm ditto is a 50 mm lens x7. And magnifies the image seventimes..

He has had both answers and can make his own choice. I'll wish himluck in this new venue..

Regards, David.

The above is correct. I understand why you gave the answer you did..

I have a fetish for resolving power. It's why I use an 800 and 1100mm lenses, and why I'm annoyed when my EXIF data says, 1200mm - It's not. And since I make a living by printing, and I print BIG; since my equipment is aimed at reesolving, from time to time, I become "picky, picky, picky...".

Once you print as large I as I do, you'd be surprised at what a detail, barely visible on 4x6, will look like at 16x20 or larger..

Dave... ..

Chato wrote:.

They match it more or less because 55mm is supposed to reflect thehuman eye. We shorten that to 50mm for convenience..

It was a matter of faith in the old days that viewfinders were designed to give a 1:1 view. That was from books, articles etc. But it appears you cant reliable do what I did with a DSLR. After I made the post I started to wonder about the method. Several people felt they were reliable in saying DSLR viewfinders varied from 0.7 to 1.0. I couldnt find the source but they might be right..

Your number indicates my SRT101 and Nikon F were pretty close to 1:1. The number you most often see is 43.3, which is the diagonal of a 35mm frame. I know that isnt right..

And of course the human eye is an "average" of human eyes..

Ive always wondered about that. We had a guy in my AF squadron that tested to 20/05 vision. That means he saw at 20 feet what I do at 5. Ive always wondered whether he saw a magnified image or his lenses and cones were just better quality than mine. His area of sharp focus couldnt have been diminished too much because he could scan the sky and pick up aircraft we couldnt see even after he pointed them out. And they werent all just on the horizon...

Slipe wrote:.

Chato wrote:.

They match it more or less because 55mm is supposed to reflect thehuman eye. We shorten that to 50mm for convenience..

It was a matter of faith in the old days that viewfinders weredesigned to give a 1:1 view. That was from books, articles etc. Butit appears you cant reliable do what I did with a DSLR. After Imade the post I started to wonder about the method. Several peoplefelt they were reliable in saying DSLR viewfinders varied from 0.7 to1.0. I couldnt find the source but they might be right..

Your number indicates my SRT101 and Nikon F were pretty close to 1:1.The number you most often see is 43.3, which is the diagonal of a35mm frame. I know that isnt right..

And of course the human eye is an "average" of human eyes..

Ive always wondered about that. We had a guy in my AF squadron thattested to 20/05 vision. That means he saw at 20 feet what I do at 5.Ive always wondered whether he saw a magnified image or his lensesand cones were just better quality than mine. His area of sharpfocus couldnt have been diminished too much because he could scanthe sky and pick up aircraft we couldnt see even after he pointedthem out. And they werent all just on the horizon..

Well, we are all diffferent. How tall is a human male? 5:10? 6:0? Varies from country by country and from year to year..

Eyesight is no different. But numbers give us a frame of reference. The guy you describe above of course must counter-balence quite a few of us... .

Dave..