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red3

full frame vs cropped sensor

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Can somone explain the benifits of a FF sensor over a cropped sensor? I have a D70 and am thinking of switching to canon because of faster focus. trying to decide on 20d or 5d. I like the bonus magnification that you get with the cropped sensor for macro and tele surface pics but the extra pixels of the 5d are very attractive.

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Hi Red,

 

I've used the 20D and the 5D a bit (but not underwater yet).

 

In my opinion, you'd be wasting your time switching from a D70 to a 20D as they are very similar cameras. Sure the 20D has a slight edge, but not worth it. Plus w/ the 20D you can't shoot a fisheye like the Nikon 10.5

 

If you can afford to make the jump to a 5D that would be worth it. This camera has a big viewfinder, big LCD, and LOTS of full frame megapixel goodness.

 

Cheers

James

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If you like the crop factor, you should go with the D200.

 

For me, I'm always torn between the two. I love the crop factor for sports, wildlife and macro.

 

But now that I'm doing some more portrait type photography, it's a killer trying to get the higher compression of tele photo lenses, but then also shoot a full length portrait.

 

i.e. with the 85mm prime I have to be about 30 feet away to shoot full length. With a full frame sensor, I could be 15 feet away.

 

And if your studio only allows for 15ft, then with the cropped Nikon you are forced to shoot at 42mm. 42mm is NOT flattering to anyone except the rail skinniest models.

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Hi Jim,

 

I've now shot w/ just about every format - LOL! FF and cropped Nikon, and FF, 1.6x and 1.3x cropped Canon.

 

Another bonus of the FF sensor is that when you are closer (the 15 feet) you get better isolation between your subject and the background.

 

Cheers

James

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FF has the advantage for macro where the limitations are diffraction limited resolution and depth of field. I posted a simple calculation here,

 

http://wetpixel.com/forums/index.php?act=S...t=20#entry80286

 

where I did the comparision of FF and cropped assuming that the final image is pixel-for-pixel identical for the parts of the image right at the plane of focus. The FF has a DOF advantage.

 

Another way to look at it is that a 5D cropped to 1.5x is still a 5 Megapixel sensor, and at F/16 or smaller aperture you will not see a difference in resolution between a 5Mpixel sensor and a 10Mpixel cropped sensor because of diffraction bluring of the image. So, worse case, if you don't have the lens to up the magnification to take advantage of the FF, the images from the FF sensor after cropping to 1.5x is just as good as that from the cropped sensor. You'll not miss the higher pixel density of the cropped sensor.

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James have a good point!!!

 

I general terms i have look last month closely to canons and have used a 20d for a test.

 

If we forget all bell & whispers that every camera housing have and look only in the image quality i dont think that nikon , as it is now , have the advance over Canon. Sorry to tell you this guys,, i am to a nikon user... but truth is truth..

About low noice in high isos is a canons think becauce they use a FF sensor.. is a myth. O.k. is true:less noise because pixels are larger but the canon 20d still have a low noice and is a crop sensor camera.

 

Low noice in high isos have nothing to do with full frame only.. is canons secret.

something that they do better that Nikon.

Full frame on the other side is always a benefite above & underwater especially if every uw photographer use anyway high quality lenses.

Imaging you need to crop you image? so how it will look if you crop a d200 and a 5D?.. the noice will be stronger or? and the size of the noice to

 

We just talk pixels now not additional features etc... for the image quality i would go with Canon and if i hade the chance again to start over i would take a Canon.

 

So if you can put some money together a Canon 5D is a exelent choice...

 

Lambis

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Actually I made a mistake in this statement.

But now that I'm doing some more portrait type photography, it's a killer trying to get the higher compression of tele photo lenses, but then also shoot a full length portrait.

 

i.e. with the 85mm prime I have to be about 30 feet away to shoot full length. With a full frame sensor, I could be 15 feet away.

 

And if your studio only allows for 15ft, then with the cropped Nikon you are forced to shoot at 42mm. 42mm is NOT flattering to anyone except the rail skinniest models.

It's actually distance, not focal length that does the compression. So I retract my previous statement as that being a FF benefit.

 

I now contend that there is NO benefit to FF sensors.

 

I would take a 12mp cropped sensor over a 12mp FF for the simple fact that the tighter FOV is "like" getting longer telephoto lens, and really that is where stuff gets expensive.

 

I'd rather spend my money on a 12mp cropped sensor and 200mm F2.8, than a 12mp FF sensor and a 400mm F2.8.

 

Canon does have lower noise, but at ISO 100 / 200 where 90% of my shots are taken, there is no quality advantage.

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I would take a 12mp cropped sensor over a 12mp FF for the simple fact that the tighter FOV is "like" getting longer telephoto lens, and really that is where stuff gets expensive.

 

I'd rather spend my money on a 12mp cropped sensor and 200mm F2.8, than a 12mp FF sensor and a 400mm F2.8.

 

Canon does have lower noise, but at ISO 100 / 200 where 90% of my shots are taken, there is no quality advantage.

 

The focal length should scale with the linear dimension of the sensor. The comparison should be made between a 300mm F/4 for FF vs a 200mm F/2.8 for 1.5x cropped. The two will give the same field of view. The one stop difference approximately compensates for the DOF and signal-to-noise difference.

 

One stop better noise performance will allow you to use one-stop smaller aperture unless shallow DOF is what you're after.

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All,

 

One difference in FF vs. DX is vignetting/falloff -- far less of a problem in cropped sensors. Using a smaller image area also tends to mitigate chromatic abberation. I think this issue is of similar importance to noise, and I've been a little surprised by the focus on pixelcount and noise, with so little said about the performance of the lens line you're buying into.

 

The DPReview of the D200 has some interesting fall-off shots comparing the 5D, 20D and D200 here . The Nikon DX has more uniform illumination than the Canons -- even thought the 20D is similarly cropped, and the focal length was adjusted for the D200 /5D comparisons, and a more "adventurous" lense was used for the Nikon (18-200) than for the Canon (17-85 and 24-70 for the 20D and 5D, resp.). These lenses aren't what most of us would shoot with underwater, of course, but it does speak well for Nikon's optical design -- in this case, good enough to win back the stops they lost to noise, because the Nikons can go to wider F values without excessive falloff (so long as DOF doesn't suffer too much). I haven't been able to find direct comparisons for the lenses I use underwater.

 

Of course, one can attack vignetting, noise, and CA in PS -- but that's not the point, is it?

 

This is all very complicated. For me, it came down to price, WA's, and surface accessories (esp. flash; the SB600 rocks). I had to compromise on noise, and use Nikon tele's I don't like quite as well as the Canon lineup.

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When I shot the Nikkor 17-35AFS - one of Nikon's finest lenses, IMO - on the full frame Kodak ProSLRn, it too had fall-off. Remember, all of these lenses had falloff when used on film camera, but it wasn't as big of an issue. Anyhow, with the 17-35, I set my vignetting slider in ACR to something like 10 and made that the default. Problem solved.

 

The main fact remains - Nikon doesn't have any fast sharp primes for use with the DX system. Where is the 20mm f2.8 equivalent? Where is the 24mm f1.4 equivalent? Making a 10.5 fisheye got them a long way, but the 12-24 and the 10.5 only gets Nikon half way there, IMO. Believe me, using the available 14mm is not the answer.

 

I just tried out a full frame sensor and a 24mm F1.4 for the first time and I was impressed. Imagine shooting ISO1600 with a wide F1.4 lens...

 

Cheers

James

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Hi red3, id be very hesitant in switching for what seem to be minor reasons. People talking about this or that having some kind of theoretical advantage, but in reality few photographers will actually encounter those perceived benefits. The D70 is an excellent camera, and since you have it already, enjoy it and learn to make even better pictures with it. If you'd already had a Canon, i'd have said the same. Stay with the Canon.

 

If you feel you're hitting the absolute limits of your capabilities with the D70, then be all means get a 5D. That should keep you going for years to come. But also consider the D200, since you already have a Nikon.

 

Cor

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When I shot the Nikkor 17-35AFS - one of Nikon's finest lenses, IMO - on the full frame Kodak ProSLRn, it too had fall-off.  Remember, all of these lenses had falloff when used on film camera, but it wasn't as big of an issue.  Anyhow, with the 17-35, I set my vignetting slider in ACR to something like 10 and made that the default.  Problem solved.

 

The main fact remains - Nikon doesn't have any fast sharp primes for use with the DX system.  Where is the 20mm f2.8 equivalent?  Where is the 24mm f1.4 equivalent?  Making a 10.5 fisheye got them a long way, but the 12-24 and the 10.5 only gets Nikon half way there, IMO.  Believe me, using the available 14mm is not the answer.

 

I just tried out a full frame sensor and a 24mm F1.4 for the first time and I was impressed.  Imagine shooting ISO1600 with a wide F1.4 lens...

 

Cheers

James

 

True -- falloff is always worse on FF. But it's also true that the (even more) cropped Canon had more falloff than the cropped Nikon. For the lenses tested in the DPReview review, the Nikon optics are simply better in this respect. And while it's easy to fix in PS, I think we all agree it's better to capture an that requires less manipulation in PS.

 

Of course, at high ISO the current Nikon sensors require more processing for noise reduction than the current Canon sensors; I hope for further improvement with the D80 or D300, which are possible upgrades for me in 2-3 years. My investment in lenses has me pretty committed to Nikon for the forseeable future.

 

I also agree 100% on lack of wide primes, and am hoping for a circa 10mm 2.8 prime soon. I'm not sure I need a lens 2 stops faster than that for focusing (esp. for non-macro shots), and stops faster than 4 or so usually suffer from vignetting (even more) and loss of sharpness, on most lenses -- and inadequate DOF for many CFWA shots. On the other hand, I'd expect the quality of a 1.4 lense to be high -- a lot of work goes into creating such a lens.

 

All the best,

Chris

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Hi Chris,

 

Good points - I think you're going to be stuck doing some processing on all of your "keeper" shots - It's a fact of life in the digital world.

 

One of the reasons I think for buying fast lenses (besides the obvious quality) is that the "sweet spot" is lower on the "f-stop scale." Most lenses are usually sharpest in their middle aperture range. So if you shoot an F1.4 lens, it may be sharpest at F5.6-f11 If you shoot an F4 lens like the 12-24, then the sweet spot is shifted to the right by 3 stops, meaning you'll need eight times more light to get into the good range.

 

Cheers

James

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Good points being made. And most seem fair to me.

 

But remember pictures will live and die (sell or not sell, get published or not get published, win comps or not win comps), on what is in the frame - how it is lit and composed (not what camera was used to take the picture).

 

Remember: too much measurebating can make you go blind (to photography).

 

Alex

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Thanks for adding some balance into the discussion Alex. It's a good thing we have a "doctor" and an "engineer" on staff, eh? :-)

 

Cheers

James

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While I agree that choosing a camera system will only play a small role in the final results, it's still worthwhile to think it through. The artistic part of photography is much more important, but it helps to understand the technical stuff too.

 

Also, knowledgeable, discriminating consumers drive the equipment makers to improve their stuff. If eveybody has the attitude that everything in all the current products are great and he'll be happy with anything he picks off the shelf, there will be no progress.

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I think that this is a good thread with lots of good point and counterpoints coming up. I am going to move it to DSLRs so it gets more attention.

Alex

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One of the reasons I think for buying fast lenses (besides the obvious quality) is that the "sweet spot" is lower on the "f-stop scale."  Most lenses are usually sharpest in their middle aperture range.  So if you shoot an F1.4 lens, it may be sharpest at F5.6-f11  If you shoot an F4 lens like the 12-24, then the sweet spot is shifted to the right by 3 stops, meaning you'll need eight times more light to get into the good range.

 

That's interesting, I did not know that and it's certainly YET ANOTHER reason for me to spend YET MORE MONEY. Thanks a lot, James!

 

All the best,

Chris

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But remember pictures will live and die (sell or not sell, get published or not get published, win comps or not win comps), on what is in the frame - how it is lit and composed (not what camera was used to take the picture).

 

Absolutely right, of course. That said, there is absolutely no doubt that my photos got way better very quickly when I went from a CP5000 to the D70. Focus speed, write speed, and negligible shutter lag all helped. And the image quality is better, too, with a better sensor and better lenses. I can SEE all that.

 

And (somewhat like Herb, I think) just because I enjoy the nerdly side of this doesn't mean I ignore the human/creative/experience side.

 

Even if ... I am ... a doctor of engineering! Bwa ha ha!

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Hi Guys,

 

Here's an interesting and very applicable quote by Thom Hogan. He doesn't like to be directly quoted like this, but hopefully he won't mind if I plug his website too...:-) He is a "tech guru" and has written many books about Nikon cameras and flashes (www.bythom.com).

 

Let's assume for a moment that 10 photons fall per square micron and that a photosite's entire area collects photons. The compact digital cameras have sub 3 micron photosites, which means a collecting area of no more than 9 microns square, so they're only going to get 90 photons. The D200 is running just under 30 microns square, so it's going to get 300 photons. Now if the underlying chip noise is 5 electrons worth, the signal to noise ratio of the compact digital is 18:1, the DSLR is 60:1. That's at base ISO. When we start amplifying the data for higher ISO values, other factors start reducing our SN ratio.

 

So if a full frame sensor has pixels 8.2 x 8.2 microns (The 5D) and a D2x has pixels 5.5 microns then the area difference is 67.2 square microns vs 30.25.. That means that according to the above, the 5D pixel will get 670 photons and have a S/N ratio of 134:1

 

Now I know Alex is going to curse me for posting all these numbers...lol :-)

 

Cheers

James

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So if a full frame sensor has pixels 8.2 x 8.2 microns (The 5D) and a D2x has pixels 5.5 microns then the area difference is 67.2 square microns vs 30.25.. That means that according to the above, the 5D pixel will get 670 photons and have a S/N ratio of 134:1

 

Well, that scaling works only if we hold everything else constant -- S/N depends on sensor details and camera electronics, right?

 

Otherwise, we would have to conclude that because the D70 (23.7 by 15.6 with 6.1Mp for about 61 sq mics) would have better S/N than the 20D (22.5 by 15 with 8.2 Mp, 41 sq mics) and the D2X (30), and virtually the same as the 5D (67 vs 61 for the D70).

 

As a D70 shooter, I am painfully aware that it simply ain't so. Canon gets a better S/N out of a smaller sensor with a higher MP count, comparing the 20D to the D70. Superior engineering can break this scaling law -- and a truly superb small sensor can have better S/N than a larger sensor (again, with different materials and electronics).

 

Calculation is like masturbation. If you do it long enough, you start to think it's the real thing. Or so I hear.

 

I think I will go take pictures of ibises with my teeny sensor but oh-so-big 80-200 f2.8!

 

Cheers,

Chris

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Alright, I know nothing about photons and how they influence resolution (my PhD is in biology!). So, let's make this really useful, here is what I gather from all of the above:

 

1) The main disadvantage of a 24mm wide (a.k.a. crippled) sensor is diffraction limited resolution. In other words, in small apertures a full frame sensor has theoretically higher resolution.

 

2) The main disadvantage of a 35mm wide (a.k.a. full frame) sensor is vignetting/falloff. The edges of the lenses produce lower quality image, which are only apparent on 35mm sensors because they are cropped out on 24mm sensors.

 

My request is, give me one REAL WORLD example of one of each of the above. One example in which you had to increase you aperture in a 24mm sensor camera because of diffraction and one example of light falloff that really bothers you. Any lens, any camera. But it has to be real world, better if it is underwater.

 

Let the games begin...

 

Luiz

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I think the general point still stands Chris - the area of the sensor is very important and bigger is better when it comes to S/N.

 

Cheers

James

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Here's an interesting and very applicable quote by Thom Hogan...

 

Wow, that's fascinating stuff, James! I had never read/heard anything that specific before - thanks for posting it!

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eh I got lost somewhere at the beginning???

 

Q. Can you still take photos? with "full frame sensor has pixels 8.2 x 8.2 microns (The 5D) and a D2x has pixels 5.5 microns then the area difference is 67.2 square microns vs 30.25.. That means that according to the above, the 5D pixel will get 670 photons and have a S/N ratio of 134:1"

 

ps. I found this thread in the Beginners Forum

 

:(:)

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