Testing123 said:
Most all the DoF calculators I have seen run with the "classic" circle of confusion size of 30 microns for 35mm film and FX.

I think you're right--the two DoF iPhone apps I mentioned earlier, I believe, default to a CoC diameter of 0.03mm (30 microns), but you can change that parameter in the app if desired.

NikoDoby said:
For future reference let's only post photos as examples that you own the rights to (no blockie faces). Trust me you can get into major trouble for that.

Copy that. Will do.

studio460 said:
Oh, crap! You do? I don't have the rights to publish those images, even though they're mine. I have to remove those!

For future reference let's only post photos as examples that you own the rights to (no blockie faces). Trust me you can get into major trouble for that.

Duh, forgot to mention:

Most all the DoF calculators I have seen run with the "classic" circle of confusion size of 30 microns for 35mm film and FX. They also treat all 1.5 crop sensors as having an acceptable circle of confusion of 20mm. This is overly simplistic. The values are dependent on print size, viewing distance, lightwell size, and AA filter strength. Use them only as a guide.

In a perfect world a DX sensor would be just the middle 1/2 of a FX sensor. It would have the same acceptable circle of confusion, and therefore the numbers would be identical (in your second 85/56 comparison).

In the real world they are not, there is not two sensors out there of different sizes yet the same density and filter characteristics, that I am aware of. Just keep in mind that CoC is not a hard number and use DoF calculators as hints and not rules.

Drdobs said:
Am I wrong?

Yes, you have it backwards. The larger the sensor, the shallower the apparent depth-of-field. The smaller the sensor, the deeper the apparent depth-of-field. That's why point-and-shoots, with their extremely small sensors, tend to shoot with very deep focus, even wide-open.

I think I'm foggy either way, but I very much appreciate your input here... I should have rephrased that statement to take into consideration the framing of the image to be as nearly identical as possible... When I do so, as your example above, I get the following...

FX: 85mm - F2.8 - 8ft from subect = 0.44ft in focus
DX: 56mm - F2.8 - 8ft from subect = 0.69ft in focus

Bingo.. I was forgetting to take crop ratio into consideration in mm length and there you have it, giving identical framing FX has a more shallow depth of field than does DX.. I suppose that's a key point for people to realize, including our topic starter and his shiny new D7000...

Now this makes me want an FX sensor again.. lol

Jon

But of course you don't have the same photo, the same framing, with a FX @ 85mm and 8' subject distance as you do with a DX @ 85mm and 8' subject distance.

Apples to Apples is a FX @ 85mm and 8' subject distance vs a DX @ 56mm and 8' subject distance.

But running with your apples to oranges comparison brings up a good lesson. The other, minor, DoF difference you are seeing is all to do with lightwell size and circle of confusion size and the classic definition of "DoF". I see an afternoonn with Wikipedia in your future. Quick answer is that the FX sensor IN THIS CASE has greater DoF when looking at pixels, while the two cameras have identical DoF when measured as a ratio of picture height. I don't know what your background is, so I'm not sure what sort of analogy to make. Either you understand the physics or you need an analogy.

Since one looks at pictures, not pixels, the DoF is perceptually the same.

spraynpray said:
Er, by a negative amount. DoF is deeper the smaller the sensor, not shallower.

That's what I always thought, however, I have a couple of good DOF calculators on my iPhone and comparing a Nikon D3 (FX) to a Nikon D7000 (DX) I'm getting numbers that show the full frame sensor has more of the image in focus, not less.

As an example...

FX: 85mm - F2.8 - 8ft from subject = 0.44ft in focus
DX: 85mm - F2.8 - 8ft from subject = 0.29ft in focus

I tried other scenerios, it is showing that the FX's advantage, due to the bigger sensor, is that it can get MORE information in focus, not less.

Am I wrong?

Testing123 said:
By what measure does DX have a thinner DoF than FX?

Er, by a negative amount. DoF is deeper the smaller the sensor, not shallower.

Drdobs said:
Yes, I clearly get the fact that when you shoot at 1.8, 2.8 versus a 5.6 or 8 you are going to get a much shallower depth of field. If that's what you're going for, the DX has an advantage as the DX sensor has an even shalloer DOF than the FX sensor.

By what measure does DX have a thinner DoF than FX?

Drdobs said:
However, sometimes you don't always want that razor thin DOF. On his D7000, if he's at 85mm focal length, 8 feet away from his subjetc at F2.8, he is going to have a in focus range of less than half a foot. Most people's heads are more than that so he'll either need to step back significantly - thus changing the composition - or shoot at a higher aperature which - negates the effect of the F2.8 lens.

Look closely at most portraits. 1/2 a foot DoF is a lot! Many many portraits have a much shallower DoF than that, often to the point of the nose being softer than the eye.

Yes, I clearly get the fact that when you shoot at 1.8, 2.8 versus a 5.6 or 8 you are going to get a much shallower depth of field. If that's what you're going for, the DX has an advantage as the DX sensor has an even shalloer DOF than the FX sensor.

However, sometimes you don't always want that razor thin DOF. On his D7000, if he's at 85mm focal length, 8 feet away from his subjetc at F2.8, he is going to have a in focus range of less than half a foot. Most people's heads are more than that so he'll either need to step back significantly - thus changing the composition - or shoot at a higher aperature which - negates the effect of the F2.8 lens.

Obviously the faster lens the more flexability you have because you can shot fast, or stop down and shoot in 'normal' aperature ranges but I'm still not so sure why people pan these nice, clean technical strong mid-range zooms... His 16-85 is 3.5 at the minimum up to 5.6 at 85mm.

Jon

Though spraynpray has nailed it, I want to mention one more thing:

Remember Focal Length / Aperture = Entrance Pupil

One really needs an entrance pupil greater than ~18mm to start getting soft background at sane portrait distances, and ~35mm to start getting into the really creamy stuff.

105/5.6 is just pushing the low end of my arbitrary scale, and never will get into the cream unless you subject is kissing close and your background is at the horizon.

FX forces you to stand closer to the subject with any given entrance pupil setup, thus sensor size is mistakenly believed to be responsible for better bokeh. It's not, but larger sensors do make pleasing bokeh much easier to achieve as one needs a longer lens to achieve any given framing, thus larger entrance pupil sizes OR a more forgiving subject:background distance ratio.

The point of the pics above is for you to compare the differential focus differences between the lenses.

i see the samples now...good point studio460.....btw why are the faces blocked? we know who they are :P

oh btw... i feel like a fat kid n d7000 is my new candy.....n my appetite has no limit.... ;) loving the d7000+16-85 combo n now the 35mm...a lil overwhelmed by the features of d7000...but whats the point if the art is not challenging :)

amazingly, the best book on d7000 is the FREE MANUAL...any new buying a dslr... read the manual prior to engaging in other books/guide

Studio 460, we cant see the samples. DrDobs, how do u like my new avataar....;) btw an offtopic question......do u guys think ill need a filter for a 35/1.8mm . ive got a 67 mm...i can easily step it down with a b+w ring..but will i really need it? i know i dont need a filter for indoor photography :P
P:S i have a hood with the 35mm

Drdobs said:
I'm a little surprised to see all the down opinions on those "slow" 5.6 lenses.. What does everybody shoot at in daylight or outside conditions? Or how about with flash? Don't they say your very sharpest images will come at the medium aperatures of between 5.6 & 11? What is wrong with those aperature numbers provided there is enough light to still shoot at 1/100 or faster?

I guess I'm still learning a lot myself but I'd love for people to enlighten me on what is so bad about these mid-ranged sharp zoom lenses.

It's not that they're "bad." It's that you can't isolate your subjects stopped down that far--there's just too much depth-of-field. The issue isn't sharpness--it's aesthetic control over your image. Also, expensive f/2.8 zooms aren't your only option. Fast, short telephotos such as the 50mm f/1.4 and f/1.8, and 85mm f/1.8 are within nearly every photographer's budget. The first two sample photos below would be impossible to image with an f/5.6 maximum-aperture zoom at the equivalent focal length and subject distance.

IMAGE DELETED

Longer f/5.6 zooms (such as the AF Nikkor 80-400m f/4.5-5.6 VR, when lensed at 400mm), are able to attain shallower apparent depths-of-field, due to their narrow angles-of-view (i.e., their "telephoto-ness"). But, with slow, moderate-length telephoto zooms (e.g., 18-105mm), it's difficult to separate your subjects from the background.

IMAGE DELETED

Too much depth-of-field from this f/3.2-irised, point-and-shoot image, above, exhibits distracting background detail.

Absolutely and like I've said before, it isn't in Nikons best interests to sell bodies with junk lenses attached.

Egh there are haters of the kit lenses, but most like me can't afford to just buy every f2.8 lens out there. I frequently see pictures in magazines that have been taken by people with kit lenses. A faster lens will increase usability, but I don't think the kits lenses are as bad as some make them out to be. When you don't make money with your camera then it is hard to justify to your significant other a $3000 lens purchase.

damn right Jon :) i got plenty of nice guides..bout 20 of them :P

Yes, you have plenty to cut your teeth on right now and you just shelled out some good coin.. Stick with this for some time, master your D7000 (I *highly* recommend the Magic Lantern Guides or Thom Hogans D7000 guide) as a manual... - there I go again, getting you to spend more $$...

I look forward to seeing your wonderful photos in the future..

Jon

likewise drdobs...i saw many samples of a d90 with a 70-300 4.5-5.6 and ill say..they were pretty darn good.... and until i can take similar photos, ill not even think bout the 2.8 version......for beginners n intermediates..i think the 4.5-5.6 will do wonders..besides anyone that has owned that lens has sung only praise for it except when its at 300... not at all bad for a 400$ lens. :)

http://www.bythom.com/70300vrlens.htm great review on the 400$ model... btw this was out of stock in the store since demand is ultra high.......

Excellent... You have a great setup there, seriously... I honestly think you made the best decision... And down the line you can think about the 70-300 vs a 2.8 lens etc..

I'm a little surprised to see all the down opinions on those "slow" 5.6 lenses.. What does everybody shoot at in daylight or outside conditions? Or how about with flash? Don't they say your very sharpest images will come at the medium aperatures of between 5.6 & 11? What is wrong with those aperature numbers provided there is enough light to still shoot at 1/100 or faster?

I guess I'm still learning a lot myself but I'd love for people to enlighten me on what is so bad about these mid-ranged sharp zoom lenses..

Jon

padlockd i think initially ill go for a 70-300/4.5-5.6 n play around with it for a few yrs...only if i develop good skills, ill gift myself the 300mm f/2.8G vrII..that station is long long away :) but its where i know ill enjoy wildlife photography at its best....meanwhile nikon can lower its damn prices on the 2.8 :P-i know they wont :(

P:S i also bought a tripod but i doubt ill be using it for now......the only thing im paranoid bout is taking care of the camera...humidity worries me as its always high here in Mumbai...lots of silica gel :P

Well i did go for the d7000 + 16-85 got a b+w kaesemann crc polarizer with 16gb sandisk extreme 10 class and an extra battery + sbs 700 n a nifty cleaning kit with a pro bag.
gf feels ignored heheheh :P
picking the 35mm/1.8 as well n after 6 mnths will think bout the 70-300......meanwhile loads n loads of reading n loads n loads of practicing....will not be in peace until i exploit the d7000...ya i ditched the 18-55 cuz i was tired of hearing that im putting worn out tires on a ferrari :P
playing mainly in auto now n i know will be a while till i go on manual...but ill come through :)))
currently playing with exposure and shooting in different light conditions... understanding exposure is a nice newbie book...that everyone should read :)))) learnt alot from that one
drdobs, how you doing :))))))

@bharatwd1:

D90 + 18-105 + 35 1.8.

Once you think you've met the limitations of that kit _as a photographer_ then move up. Learn the ropes on the D90, and then possibly get the D7000 replacement or move to full frame if you think you're going to make a living off of photography. Remember, a LOT of people have D90s right now, and if you look of flickr there are tons of great pictures taken with that camera. Don't think you need all the latest and greatest.

As for the 70-300 VR, it's slow. I would skip it. If you find you really want to get into wildlife (because you only have a max of 105mm), go for something with 2.8 or faster. 70-200, 300 f/4, etc. You will hate f/5.6.

I would advise not to bite off more than you can chew...