For the digital camera gurus ... can somebody explain to me the real translation of lens size from normal 35mm film lens to digital cameras?

What I mean is this. In this 35mm world ...

a 50mm lens is normal 1x ... what your eyes see in real life in terms of degrees
a 200mm lens is 4x meaning that an object 4 times farther away from you will look like its right ther
as 500mm lens is 10x, etc.

The inverse inverse is true for wide angle

24 mm is much ider but looks farther away than you really are etc.

Now ... from what I understand, the sensor size on all but the most expensive DSLRs are 1.5 or 1.6 conversion factor because they are much smaller than a 35mm negative.l

Thus ...

using a 50mm your image is cropped ... your missing the stuff on the side so for 1.6 conversion its really, in terms of width, more like a 80 mm lens ... EXCEPT you do NOT get the magnification of an 80? True?

In other words, a 200 mm (4x) using a 1.6 conversion yields the "image" area you would see in a 329 mm lens but your still only 4x closer ... that bear doesn't look any closer unless you buy a 300 mm lens but the image would again be cropped more.... TRUE????

The inverse would hold true on wide angles.

If a kit lens said 18mm lens its really a 29mm len (not really wide at all) so if you really wide a wide angle, say a 24mm you would need to buy a 15mm lens ... True?

Is this making any sense?

I ask because I read ppl writing their 200 mm lens is really like a 320mm lense and think ... yes, in terms of image size ... no in terms of getting any closer to the subject. ... its not 6x.

Any one?

 

35mm film: 35mm wide
Nikon D-SLR Sensor: 23.6mm wide

So the ratio of 35mm film to a Nikon D-SLR = 35/23.6 = 1.48 = ~1.5

What you have with a D-SLR is a "sensor crop", basically, for the same lens, the angle that is covered is smaller with a D-SLR because the sensor is smaller than a 35mm film frame.

Basically if you start from the same vertex, the angle that is available to be included in the frame is smaller with a D-SLR than a 35mm film camera, because the sensor is smaller.

As a result, the lens is effectively "magnified" by a factor of 1.5 (Nikon) or 1.6 (some Canon).


What does this really mean to you?

1) For Telephoto, a d-slr is more cost effective to achieve the same image size/crop because the sensor size means that where a 200mm lens shot with 35mm would be 200mm, a 200mm lens shot on a Nikon D-SLR would effectively be a 300mm in terms of what would appear in the framing.

2) D-SLR users get SCREWED when it comes to wide angle, because even 12mm shot on a D-SLR would have effectively been 18mm on film.

Make sense?

 

Chows

Everything you said is true. The sensor being smaller in the D-SLRs, there is a Field of View (FOV) crop. While the image magnification stays the same, effectively, the image you achieve is a crop. This crop is defined by the dimensions of the sensor vis-a-vis a standard 35mm film negative. So for Canon D-SLRs, the FOV crop is 1.6x/1.3x and for Nikon, it's 1.5x.

If you want better telephoto zoom, get a longer lens, not a FOV camera. For wide-angle, like Dave mentioned, the D-SLRs come up short. You need to get ultr-wide angle (for example Canon EF-S 10 -22mm) to get an equivalent FOV of a 35mm film/full-frame camera.

 

Please dont forget that many Digital Slr's made by both Canon and Nikon have full size sensors and therefore no conversion is required
Examples of this would be Eos 1DS ,1D ,1DS MK 2, D2H, D2X

 

So Dave and Sasha ...

I think I do have it right.

a 200mm lens shot on a Nikon D-SLR would effectively be a 300mm in terms of what would appear in the framing.

But simply because its cropped ... not because its 6x closer

While the image magnification stays the same, effectively, the image you achieve is a crop.

This confirms what I'm saying above
If you want better telephoto zoom, get a longer lens, not a FOV camera.

What does this mean, don't get like a D80 because its 1.5?

You need to get ultr-wide angle (for example Canon EF-S 10 -22mm)

I've looked at that lens, looks like 14 - 35mm which is a great wideangle zoom range.

A few more questions please

Is the Canon L glass really all that much better than the consumer lens. I mean one L lens cost more than a D80 body.

My wife uses her camera everyday and really wants the wide angle but the EOS and larger SLRs were too big. Xti or D80 were about perfect. Only real wide angle I could find were the 10 - 22 Canon. 17 - 40s are 28 - 65 ... not really wide at all. Any ideas?

What do you think about a 10 - 22 (14-35) and a 50 (80mm) to cover most normal indoor stuff or landscapes outside?

And one last question please ...

Im looking to make 11 x 14 prints. If I go buy like a Canon G7 10 mpixel and compare it against an equivalent 10mpixel taken buy a Canon or Nikon DSLR, is there really any difference in the quality of the pictures your eye can see.

In other words, for example, a 17 - 40 Canon L glass lens cost about $700. Thats more than the G7 camera. But, do you really get a better pic you can actually see?

 

D2H and D2x are still 1.5
Jim

 

Chow4us: I recently moved from the digital point and shoot to a DSLR (Canon 400D/XTi). While it was like going back in time to big cameras, lots of lenses and heavy bags, it was also familiar. After reading thousands of posts on dpreview, POTN, FM Forums, etc, I ended up with a Tokina 12-24, which is a great lens and a reasonable alternative to the UWA Canon zoom. I also got a Canon 70-300 DOIS, which is not an L lens, but wonderfully compact and the IS is amazing. I initially bought a Sigma 30 and a Canon 50 to fill out the middle (the kit lens is carp) but then got a 24-105 L. As you said, incredibly expensive, but ultimately good value as bodies come and go, but lenses are forever. Although some redundancy with the primes and the zoom, the kit gives me flexibility. I love the relatively small size of the 400D, even with these lenses. The crop factor is a pain at the wide angle end, but the UWA optics are pretty amazing when you think back just a few years and compare what was available.
Anyway, your analysis was spot on concerning crop cameras, but it's a balance between size, cost and quality.
wrt your last question: I bet the G7 is capable of making some wonderful images. I've seen superb photos from a G1 and every PnS in between. I don't think I'm making better photos with my new camera than I did with my Digital Elph, other than having more flexibility and more pixels to work with.

btw, I've just discovered dust on the sensor--a problem with DSLRs that never seemed to occur with PnSs. Now this is a pain...

cheers,

 

Dr. Phil ... My thoughts below and your comments please ...

I am right now where were... Decision time ... basically for my wife. She is the one who uses the camera every day.

To give a bit of backround, I used to have multiple Minolta Maxxum bodies with full frame fisheye (useless), 24 MM, mid-range zoom, 100 - 300 zoom, 400mm and 500 mirror. They are all gone years ago, time to move and and too heavy to lug around. Got a NIkon 5000, 5Mp, worked great for 4 years, now its falling apart ... so what to buy?

Checked out the G7 but its tinier than than 5000. Its simply too small, buttons to small ... fed up with tiny cameras and cell phones.

We went to a store today to compare d80 vs xti.

D80 definitily bigger and heavier. Lens hard to come buy. vanted 18 - 200 not out for another 6 months. NIkon UWA $1K and very poor reviews. Salesman hinted of new Nikon lens coming in Jan. I basically wrote of the D80 ... much heavier ... evertthing more expensive.

Xti was a bit small for me (D80 perfect) but PERFECT for the wife's hand she loved it. Decision made ... Xti, now which lense?

By far, the most important thing to her is wide angle. 17mm is just not wide enuff for her indoor shots. 5000 is 17mm so she knows. That leaves the 10 -22 or Tokina. See http://www.photozone.de/8Reviews/index.html I too have read every review in existence. They like Tokina but Canon a bit better but more money ... a wash. OK, I can get one of those.

Now the mid-range. 17 - 40 has too much overlap. I too thought 50 because they are sharp (and cheap). Ultimately I came to the 24 - 105L ... SO ... what do you think of it. Everyone loves it. L Lense ..., this one you keep. Good for walkaround, vacation, etc. Good for groups of ppl or portraits.

That leaves Telephoto. Used to do MUCH wildlife photograpy, 300mm minimum ... usually 400. the 70 - 200L is highly regarded and cheaper than the UWA. My ONLY problem with that is that you dont get 320 magnification ... its just a cropped image. I also tried the 70 - 300 with IS today (not DO). Same weight as the 24 - 105L. What do you think, the 200L lens or 300 non-l with IS? Same price. Not going looking for wildlife anytime soon so no real rush. I am leaning to the 200L simply for the quality and you dont need IS for a 200mm lens.

As to dust ... I thoug the XTI has a sensor cleaner ... I quote:

I can tell you it works as good as advertised.

Tourist for one week visiting animal reserves in Sidney, I switched lenses constantly, even in the car with the air conditioning on (one of the worse scenarios to perform lens changes which you seldom notice.) The few dust specs I could find on some pictures (all shot in the period when I DEACTIVATED the automated cleaning feature to check how it worked) were COMPLETELY GONE after the next cleaning up.

http://www.fredmiranda.com/reviews/s...hp?product=306

Commets? Ideas?


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The focal length is the same. What you have is the same field of view you would have with a 300 mm lens on a 35 mm camera.

Quote:

Right. Position determins perspective, not focal length or crop. Quality issues aside, from a given camera position and a given subject, shooting with a 200 mm lens and cropping to the field of view of 300 mm lens gives you exactly the same image.

Quote:

Not really. Again, it's exactly the same.

Really, the only reason we even talk about a "crop factor" is that current DSLR cameras, with a few exceptions, are derived from 35 mm cameras and take the same lenses. But do we think of 35 mm film cameras as having a "crop factor" compared to medium or large format?

Mark

 

Now I'm more confused. Let my try to say this in words I understand.

If I use a 35mm film camera with a 200mm lens of an object. That focal length will make the object look 4x closer than the eye (50mm). Similarly, if I use a 300mm lens, its 6x. Taking wildlife photos, 300mm is about the minimum with 400 (8x) better.

Now take that 200mm lens picture and crop it to the FOV of a 1.5 conversion factor and the FOV is that of what you would see with a 320mm lens ...

But ... I've cropped the picture. I do not bring it 6x closer to me ... its still 200mm lens.

The resolution HAS to be worse ... its no different than blowing it up and everytime you blow up a pic ... 8 x 10 to 11 x 14, for example, it looks worse. That is were resolution is so important.

So are you saying it IS really 6x (for a 200mm) but what about the resolution???

Can I reasonably use a 200mm lens and get the same results as a 300mm lens in a film camera? (that would be good).

35mm is cropped 4 x 5 negative ... much smaller. Their focal lengths do not match a 35mm lense to get the same levels of magnification. Since virtually nobody but professionals demanding the best resolution use larger formats, nobody thinks in those terms.

However, the reasoning is the same. If you cropped a 4 x 5 down to 35mm you have to be loosing the resolution and whole point of a larger format film?

 

It is confusing and I probably haven't helped things with that post.

You're right that it's still a 200 mm lens and that's an important point. You'll see people say thing like "a 200 mm lens becomes a 300 mm..." and that's very wrong. A 200 mm lens is always a 200 mm lens and it doesn't matter what, if any, camera it's mounted on.

But a 200 mm lens on a 1.5x "crop factor" camera will have the field of view of a 300 mm lens on a 35 mm camera so, assuming no quality issues, you'll get exactly the same picture as you would have with a 300 mm lens on a "full frame" camera.

The resolution would be worse if the 1.5x crop factor sensor has fewer pixels than the "full frame" sensor", but remember that the pixel density can be different. You can have a 12 megapixel 1.5x crop factor sensor and a 12 megapixel full frame sensor and in that case the resolution would be identical. (And there are also issues with digital sensors having problems with rays striking them at shallow angles so, sometimes, you get greater quality on the edges and corners with smaller sensors.)

It can be the same or different depending on the pixel density. You're completely right that, if you took a shot with a 200 mm lens, on digital or film, and then actually cropped it so that you had a smaller field of view, the quality would suffer. That's why we actually use lenses with different focal lengths and don't shoot everything with a 14 mm lens and then crop to get the field of view we want.

Yes, definitely. A shot at 200 mm with my D2x looks better than a high-quality scan with my F100 at 300 mm and of course the field of view is the same. That's why sports photographers tend to like the 1.5x crop factor cameras (and the 1.3x and the 1.6x which I guess some Canons are). We tend to shoot a lot with long lenses and there you gain. I'd rather have a 12 MP 1.5x camera than a 12 MP full-frame camera. (Now an 18 MP full-frame camera would be fine, too, since you could crop and still get the same resolution as the 12 MP with the same field of view but of course if you're doing that a lot you've spent money for a sensor with pixels you aren't using.) The "crop factor" only becomes a problem when you want to shoot wide and you need wider lenses for the same fov.

Yep, that's right. Also, nobody uses their 4 x 5 camera lenses on a 35 mm camera but you can use your DSLR lenses on a 35 mm camera (most of them, anyway), so you tend to think more in terms of a crop factor.

Yes. The difference between that and digital, though, is that different digital sensors can have different pixel densities but the grain density on any given piece of film of the same type is the same regardless of size.

Hope that was more helpful than confusing!

Mark

 

Mark

THANK YOU. I think I finally got it. Especially when you explained why sports photographers like the crop cameras ... simple ... instead of lugging around those old 600mm lens, the could use a 400 and still the the same FOV.

That works great on the telephotos ... but suckss on the wide angles.

I also get the resolution thing now. Pixels are not the same as grain in film. 10mp packed into the same space are. but 10Mp in a small space vice 10mp in twice the space actually is better resolution

Thank you so much!

 

Chow4Us: The 24-105L is a great lens and it seems you agree. If you are leaning toward the 200L then that too is a keeper for life. All UWA lenses on crop cameras are pushing the laws of physics (to think they can make a 10mm lens is pretty amazing) and they do suffer from some optical flaws such as distortion and CA, etc. I notice most reviews talk about these problems and indicate whether they are managable or not, with post processing.
So it sounds like you wife has gone with the XTi? I am not so enthusiastic about the sensor cleaning as others, but YMMV I guess.
cheers,

 

Also remember that the optical resolution offered by the lens (focused image
at the film plane or sensor) is limited by the laws of physics (optics),
and you may not get as much final resolution of the image in a 10 Mp
(0.7 inch by 1) CCD as in a 10 Mp full frame 35mm (1 inch by 1 1/2),
unless the digital lens is 1.5 times sharper than the full frame 35mm lens.
You can only resolve so many lines/mm optically.

 

Chows,

Without getting into the techno speak you guys have been exchanging, let me put it simply: A 200mm f 2.8 lens, when attached to a digital body such as Nikon D2x, becomes a 300mm 2.8. This is because the sensor size is smaller than the 35mm film size of a traditional 35mm film camera. And, on the wide side, a 17mm becomes a 24mm. There are trade offs. Ultra wide lenses tend to have nasty distortion of all sorts. But on the long side, 70-200 zooms become extraordinary!

 

Everything I've read says the 24-105L rocks.

As to the UWZ, actually they are both excellent ... nothing a little photochop can't fix

As to the Xti, see https://www.northamericanmotoring.co...ad.php?t=84170

The short version seems to be Nikon DX lens are inferior quality compared to the other Nikon lens which are huge money. Wife likes the smaller body to fit her hand. 24 - 105 is perfect walkaround lens. 70 -200L is cheap for what you get, highly recommended. I'm not bashing the D80 kit lens but its not getting great reviews (the lens, not the camera)

Cristo ... that makes sense THANKS!

Dmini ... yeah, I figured out the UWA gets the short end of the stick but its great for the telephotos!

 

....wouldn't the DOF and amount of compression be different?

 

Compression, no. That's a result of position. I know that's counterintuitive but it's true. DOF, that's true. Here's a good article about that:
http://www.bobatkins.com/photography...igitaldof.html

Mark

 

Y'all have got the gist of it, but to refine a bit. A 'normal' lens (giving a normal field of view) for any format camera is a going have a focal length in mm aproximately equal to the diagonal measure of the negative or sensor.

In the case of 35mm film, the film itself is 35mm wide by some length. As we look at a negative you'd say 35mm tall. A regular 35mm camera makes a image 24mm tall and 36mm wide.

What defines the view or magnification though is the diagonal measure of this image which is about 48mm. Hence a lens to give a 'normal' angle view is going to be about 48mm, rounded to 50mm nornally.

A wide angle with half the magnification of a normal lens will have a focal length half the diagonal measure, or .5x = 24mm for a 35mm camera.

For a '35mm' camera (with a 48mm diagonal measured image) then a 2x telephoto will have 2x = 96mm (100mm), and a 10x= aprox 480mm (500mm).

So instead of trying to figure equivalances, just find the size of the sensor for the camera in question and calculate the diagonal, then you can work any magnification from there.

Oh, and very wide angle lenses (small mag factors) don't HAVE to have all kinds of nasty distortion, but almost all do have some and it's correlated to cost. If you want a wide angle (very wide) angle lens that still yields a correct image (straight lines are still straight) then you want a rectilinear lens.

 

Hmm... Rectilinear.

I'm still hoping for the digital industry to create afforable and viable bodies for lenses like my Zeiss Distagon 4/40 and Leitz 21 2.8. Sadly, these two awesome wide lenses have become full time residents of my traditional photographic equipment storage bin. Hey, we can dream.

The one thing for certain in photography these days is that the digital frontier is still in its infancy and no optics or bodies are "keepers" any more than your latest pda phone. Don't believe me? Archive this quote and check back in five years.

 

I wholeheartedly disagree, at least as far as optics are concerned. If no optics are "keepers", then you might as well chuck your Zeiss and Leitz lenses into the dustbin right now.

 

You did miss my point. THEY ARE IN THE DUSTBIN! These two lenses are backwords compatible with 40-year-old cameras, but not likely forward compatible as many camera companys struggle to reinvent themselves as they morph into the digital realm. Unfortunately, digital technology is so transitional that matters like sensor chip size will remain volatile in years to come, which has a HUGE impact on the entire photographic industry, including lenses.

So, maybe I should have said, "if you find a lens that's a keeper, use it and use it daily because it's on a technological fast track just like your pda phone."

 

That's entirely possible. I thought you were lamenting a lack of system integration, not that your lenses were inferior by today's standards.

IMHO: The technology of high quality optics is not nearly as transient as that of a PDA. A Canon L series lenses will not be orphaned for many years to come.

 

I have to agree with this. I've done a LOT of reading the last few days researching all of this and most every website says the same thing.

First, crop cameras are not going away. Camera makers want both markets ... amatuers and professionals so if you think a full frame digital will come down in price to under $1K ... it may never. They want to sell the high end lens to those guys and the cheaper lens to the amatuers who do not want to spend $1K for any lens.

Second, Canon seems to be at the forefront and marketing lead. Nikon used to be but no more. Canon is vertically integrated (whatever that means). They specifically want to keep the crop camera and full sensor camera separate markets. Although some think the crop cameras and EF-S will go away, Canon keeps putting them out.

Specifically, several reviews say their 10-22 and 17- 55 EF-S lens use L series glass. Their optics are just as good (just look at the resolution graphs at photozone.de). However, they do not want the professionals to buy those lens for crop cameras so no L designation and the bodies are plastic vice the metal and sealed bodies of the L line.

See http://www.imatest.com/docs/sfr_MTFplot.html that explains the resolutions and how they equate to different cameras vice the resolutions of the lens. The 10 -22 resolution is BETTER than what the 8mp XT can produce (but not the 10mp Xti). So I dont see how these quality lense will become obsolete if they cant produce "better" lens.

Look here http://www.imatest.com/docs/sharpness_comparisons.html to see camera comparisons ....

A nikon d70 is at 1897 best in the center. Many of the quality lens produce over 2000 meaning its a waste of money on that camera.

Secon

 

Hang on a second here. My few years old Nikon wide angle primes and zooms are currently orphaned. What good is my 16mm fish eye on the current pro Nikon D2xs camera when I get <90 degree field of view. If I want to upgrade to using a D2xs for my landscape photography, I do have to junk all of my wide angle Nikon glass because it's no longer wide on APS sensors. [Not gonna happen anytime soon, so no calling dibbs on speednut's lenses. ]

Chows, stop splitting hairs, flip the coin, and start taking photos already. Nikon & Canon both have great systems, strong points and aggravations, plus compromises, but either system will make a good investment for your goals. It's time for you to really annoy a camera salesperson and spend several hours fiddling with some camera models to see which tool works best for you. Bring a CF card for test shots in the store and make sure to take some RAW test photos too.

I haven't felt the need to browse dpreview lately; wonder why?