[palmor]

Your definition of reach is hilarious because you turn around and describe FOV. Reach has to do with magnification. The focal length of a lens is what determines the magnification at which it images distant objects. The FOV changes because of the change in the sensor size. In this case the size of a 35mm negative and aps-c sensor. The crop factor or focal length multiplier is used to get the equivalent FOV.

Some people understand that it is referring to FOV. Because it is stated as equivalent focal length there are many people that don't. In this particular example, I think reach is more important than FOV. If you were to take a picture with a 500mm lens on film and with a K200d, and were to crop the negative during scanning it, you would get a similar print.

The point being, regardless of which camera a 500mm lens is on, it is still a 500mm lens. T he magnification will be 10x on a SuperProgram or K20d. It isn't going to be magnified any more. Sure, you can do a "digital zoom" but that is similar to enlarging a negative in the dark room and the digital image is pre-cropped.

Maybe Falconeye or Wheatfield can do a better job of explaining this.


Also, it would be good to leave binoculars and telescopes out of this because of the eye-piece role in magnification etc.

I see the confusion you describe quite a bit and agree 100%.

It is one of the things that annoys me about Pentax, that they bring out FOV equivalents of their old lenses. For wide angle lenses it makes sense but not for Tele's. For example the 50-135 f/2.8 is the Pentax FOV equiv of the 70-200, but it doesn't really replace the reach of a 200mm lens.

Anyway another way for people to think of this. Take a wide screen TV and an old normal 4:3 TV. The wide screen is FF and the 4:3 is a crop sensor. Take the picture you get from the 4:3TV and put it in the wide screen TV. It is the same picture with black bars on either side. Now fill in those black bars, that the FF picture.

It is the same exact picture but the wide screen TV has data you don't see on the 4:3 TV. Now project that picture into an 8x10 piece of paper. If you cropped the wide screen picture and took off either side you'd have the SAME EXACT print. No different. It is just the 4:3, aka crop sensor, is already cropped by some factor (1.5 for Pentax users)

Hope that makes sense


John

[palmor]

]OK, but its also only FOV that 99% of photographers care about when discussing different focal lengths, so I don't see the problem. Sure, it could be worded more precisely, but it's also standard industry practice, and most of us know what is meant.

I couldn't disagree with this more for long telephoto lenses so I guess I'm in the 1% . I don't care at all about the equiv. FOV on a crop sensor. I want to know the magnification of the lens I'm using. Actually I think crop sensors are at a disadvantage for things like Birds in Flight because it is much easier to track something with a wider FOV.

John

[gnaztee]

Please explain in what way "how much you see" differs from "reach". Here's my answer: they don't. A print of a given size taken with a 500mm on APS-C will look virtually identical in terms of "reach" to a print of the same size taken with with a 750mm lens on 35mm film. Only subtle differences in DOF might give away which was which.

Now, if we were talking about binoculars rather than cameras, there would be n obvious difference - magnification while looking through them. And I suppose one *could* compare cameras this way - and in that case, I'd agree the 750mm lens on the film camera wold produce a larger image in the viewfinder. But cameras are not binoculars - we judge them by the image they take, not what you see in the viewfinder.



OK, but its also only FOV that 99% of photographers care about when discussing different focal lengths, so I don't see the problem. Sure, it could be worded more precisely, but it's also standard industry practice, and most of us know what is meant.

Why would someone want more "reach"? So the particular animal fills the frame, right? So if a print from a 200mm lens on my K10D looks exactly like a print from a 300mm on a 35mm film camera, aren't they equivalent? Why do you guys freak out about this every time someone brings it up? It's silly. Would it be nice to not worry about "equivalents?" Sure, but photo books are still in publication that tell you what minimum focal lengths to use for wildlife shooting with film, and it's nice for some (especially new users) to have some help to make their digital SLR lens choice match the suggestions of these pros. I just don't get why this bothers people so much, everyone understands what's being said by camera makers when they present "35mm equivalent."

Todd

[Blue]

Why would someone want more "reach"? So the particular animal fills the frame, right? So if a print from a 200mm lens on my K10D looks exactly like a print from a 300mm on a 35mm film camera, aren't they equivalent? Why do you guys freak out about this every time someone brings it up? It's silly. Would it be nice to not worry about "equivalents?" Sure, but photo books are still in publication that tell you what minimum focal lengths to use for wildlife shooting with film, and it's nice for some (especially new users) to have some help to make their digital SLR lens choice match the suggestions of these pros. I just don't get why this bothers people so much, everyone understands what's being said by camera makers when they present "35mm equivalent."

Todd

Have you ever cropped a photo in the dark room when enlarging or after scanning a negative or positive? The crop factor is NOT an optical zoom. The issue is that people are mislead to believe a 500mm lens is a 750mm lens. If that were really the case, The DA 70 ltd would really be marketed as a DA 105mm ltd lens. Pentax is loosing something between the engineers and marketing. What the crop factor is for is FOV. It could be argued that the aps-c is a loss of image or negative.

When I use my Sigma 105mm macro lens, it still has a 1:1 macro capability whether I use it on my SuperProgram or the K20d or the K200d. If I take a pic of a bug at 1:1 on film or digital, it is still at life size. There will be more vegetation or what ever on the negative than on the digital image. However, if I scan the negative it can be cropped. Or it can be cropped in the darkroom at the enlarger. So the print analogy isn't a good comparison for focal length.

Focal lenth is focal length and FOV is FOV.

[Blue]

As bad as I hate to do this I will post this link. It uses bird photo as examples.

If you look at the bird in flight in Case 1 with a 200mm lens on film and digital, you will see that the bird on the film shot is actually the same size as the shot on the digital. The difference is there is more sky on the film shot which can be cropped following a scan or enlargement.

Focal Length Multiplier: Optical: Glossary: Learn: Digital Photography Review

In Case 2, a 300mm lens is used on film to get the same FOV of the 200mm on the digital. The bird is bigger on the film with a 300mm lens than on the 200mm with digital. However, the FOV is the same.

Class dismissed.

[gnaztee]

Not so fast my friend. In example #2 of the DPR link you provide, if I print both of those at 4 x 6, they look the same, no?

[gnaztee]

And I understand the difference between FOV and focal length, but again, most understand what is meant when this is said. Essentially, we could say: "The same scene taken with a 300mm lens on 35mm film will look the same, uncropped, as it would taken with a 200mm lens on an APS-C sensor, uncropped." Yes?

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Last edited by gnaztee; 03-15-2009 at 10:33 PM. Reason: lost a comma

[Blue]

Not so fast my friend. In example #2 of the DPR link you provide, if I print both of those at 4 x 6, they look the same, no?

This is the text from example 2:

Information projected by a 200mm lens onto the sensor with FLM of 1.5X. The Field of View is the same as the 300 mm lens on the 35mm camera. The absolute size of the bird projected onto the sensor is smaller compated to the 35mm film because a lens with shorter focal length is used (different magnification).

[Blue]

And I understand the difference between FOV and focal length, but again, most understand what is meant when this is said. Essentially, we could say: "The same scene taken with a 300mm lens on 35mm film will look the same, uncropped, as it would taken with a 200mm lens on an APS-C sensor, uncropped." Yes?

While you may understand, why use incorrect terminology that confuses other people? That is particularly important in a thread regarding a long telephoto (or tele zoom) lens. What is wrong with saying equivalent field of view? However, wildlife photographers are often trying to get a picture of critters in the forest and not necessarily of the forest so the crop factor on a telephoto can be a benefit where as on a wide angle for landscape and architecture it is a disadvantage.

[palmor]

Just another way to think of it...

Take a crop sensor at 10MP, the FF equivalent would be a 15MP sensor.

Scenario 1
* Take a photo with a 200mm lens on a crop sensor, you have a 10MP photo that fills a 8x10 piece of paper.
* Take the same photo with a 200mm lens on the FF sensor. At 1st you have a 15MP photo that "appears" smaller on that 8x10
* Crop the FF photo by 1.5x. You now have the same exact 10MP photo you did on the crop sensor.

Scenario 2
* Take a photo with a 200mm lens on a crop sensor, you have a 10MP photo that fills a 8x10 piece of paper.
* Take the same photo with a 300mm lens on the FF sensor. Now you have a photo that "looks" the same as the crop sensor one when printed out on a 8x10 but it is 15MP in size.
* To make things fair NOW crop that 15MP photo by 1.5x. Now you have a 10MP photo that appears to be much closer then the crop sensor one... and because you took the photo with a higher magnification lens you will have more detail, especially in the fine detail (feathers, fur, leaves ect).


John

[rfortson]

So my question are what would a scope give/not give me that a reg camera lens will give me?

Thanks
Jim

I have the Bigma and the matching 1.4x TC and I agree with you that it makes the shot soft. However, I've seen others that have gotten good results with that pair, so maybe it's me or my combo.

Anyway, to get much longer, you'll have to spend a big chunk of change. For what you'll spend (if it's even available) you could probably just buy the land you're shooting on.

I'm not sure spotting scopes are the answer. If they were, I think we'd see many more shots with them. I could be wrong of course.

I think this may be a case of where "a man's got to know his limitations"

[Blue]

. . .

I think this may be a case of where "a man's got to know his limitations"

That's an ironic quote for this thread since it comes from a man packing a 44 magnum! He stated in a sequel when asked by his lady partner why he carried a 44. "I like to hit what I shoot at."

[Marc Sabatella]

Your definition of reach is hilarious because you turn around and describe FOV.

Right - because my point is, these are one and the same. It is impossible to alter one without a corresponding change in the other. There is no way to create a lens that provides more "reach" than another on a given camera except by having it create a narrower FOV. And vice versa. Similarly, it is impossible to create a camera has a cropped sensor compared to another - and thus a narrower FOV - without also increasing the "magnification" of any lens attached, assuming you print your pictures at the same size.

Now, it is true the size of the image *on the sensor* won't change with "crop factor". Thus, in this sense, we could possible say that magnification hasn't changed. This will become relevant on the same way someone invents a device that allows us to actually see that image. But in the world as it exists today, the only way to see an image captured by a sensor is to display it on a screen or print it. And assuming one does so at the same size, you get the same magnification aka "reach". There is simply no *real world* sense in which there is an difference whatsoever between FOV and "reach".

Looked at another way - or, rather to restate what I wrote before - if you take a picture on a 35mm film (or "FF" digital) camera with a 450mm lens and I take one of the same scene on an APS-C digital camera with a 300mm lens, and we both make prints of our images, no one on this earth could tell the difference based on "reach" - it will be identical.

If you were to take a picture with a 500mm lens on film and with a K200d, and were to crop the negative during scanning it, you would get a similar print.

Indeed, that is exactly how the crop factor works. It's also *exactly* what happens if you shot with a 750mm lens on the film camera. By the time you make the print, there will be nothing whatsoever about it that would possibly allow anyone to tell whether it came from a 750mm lens on film or a 500mm lens on the K200D.

The point being, regardless of which camera a 500mm lens is on, it is still a 500mm lens.

No doubt there - I do realize that "focal length" has a precise definition and that this does not change. But when FOV changes, so does reach when dealing with the real world of prints and images made visible on screen.

The magnification will be 10x on a SuperProgram or K20d.

10X? Ten times what? The image will be tiny on the negative itself or on the sensor - clearly not 10 times actual life size. And you can print the image at whatever size you want. It could be printed on a postage stamp and be a small fraction of life size, or be printed on a billboard and be many times larger than life. Maybe you meant ten times larger than a simlarly-presented image made with a 50mm lens? Perhaps - I'm not sure how the math works out there. But there is nothing particularly special about 50mm in this context. And in an event, given that the printed or otherwise-presented image from the 50mm lens will also have more "reach" on than the K20D than on the Super Program, this argument doesn't actually demonstrate anything.

Also, it would be good to leave binoculars and telescopes out of this because of the eye-piece role in magnification etc.

Indeed, but it was really the only sense in which I could see there being any real world difference between 450mm on film and 300mm on APS-C.

[Marc Sabatella]

I couldn't disagree with this more for long telephoto lenses

Please explain, then, how exactly a picture taken with a 135mm lens on a Pentax DSLR differs from a picture taken with a 200mm lens on a 35mm film camera. That is, given a print made of both images, how would you know which was which? or is it simply that the viewfinder on the film picture provides a larger view of the same scene? that much is, as I already mentioned, certainly true.

[Marc Sabatella]

Just another way to think of it...

Take a crop sensor at 10MP, the FF equivalent would be a 15MP sensor.

Scenario 1
* Take a photo with a 200mm lens on a crop sensor, you have a 10MP photo that fills a 8x10 piece of paper.
* Take the same photo with a 200mm lens on the FF sensor. At 1st you have a 15MP photo that "appears" smaller on that 8x10
* Crop the FF photo by 1.5x. You now have the same exact 10MP photo you did on the crop sensor.

Yes, although I believe you'd actually need a 22.5MP sensor to have the cropped image come out the same pixel-by-pixel - it needs to be 1.5X the size in both directions.

Scenario 2
* Take a photo with a 200mm lens on a crop sensor, you have a 10MP photo that fills a 8x10 piece of paper.
* Take the same photo with a 300mm lens on the FF sensor. Now you have a photo that "looks" the same as the crop sensor one when printed out on a 8x10 but it is 15MP in size.

Right, and as far as I am concerned, that's the end of the story. Most of what after this is a function of having more resolution on the 15MP (actually 22.5MP) camera, not because of any difference between the lenses.

* To make things fair NOW crop that 15MP photo by 1.5x. Now you have a 10MP photo that appears to be much closer then the crop sensor one... and because you took the photo with a higher magnification lens you will have more detail, especially in the fine detail (feathers, fur, leaves ect).

You'll get more detail mostly because you have a higher resolution sensor. Now, if the 300mm lens *happens* to provide more absolute resolution than the 200mm lens, then you might also get a contribution from that effect. But merely being a 300mm lens won't magically give it more resolving power than a 200mm lens.

Now, don't get me wrong - in another thread, I tried arguing a similar thing to what you are saying here: that the 300mm lens on FF/35mm would provide more resolution than the 200mm lens on APS-C, all else equal. Folks did a pretty good job of convincing me that thijust wasn't likely to be much of an issue in practice.

And in any case, now we're arguing about fairly subtle points of resolution and which lens will produce more resolution than which on a sensor of a given pixel count, and ther are just tons of variables at play here. This is a totally different discussion than the general one about the difference between "reach" and FOV. The statements made earlier implied something far more than just subtle difference in resolution that might or might not be visible depending on the relative quality of the lenses or the number of pixels on each sensor.