Swings and Roundabouts

[jon_savage]

<p>Following on from recent threads (the DX lens Numerology and Long Nikon Primes... Fancy a 400mm F4 AFS VR?) it got me thinking about pros and cons of FX v DX for the final print.<br /><br />For fun assume the following two wildlife photographers. First with a 12MP DX shooter with a 400mm f2.8 lens at f2.8 1/500th shutter. He takes his picture of an eagle on a branch 75ft away. According to DOE master the total DOF at 75 ft with this set up is 1.19 ft. He prints it out and hangs it on a wall. Looks good, the bird sharp and in focus.<br /><br />At the same time the second photographer with him has a 12MP FX but with a 600mm f4 lens and he takes a picture. Same bird, same branch, same distance (75ft) away. Takes a photo at 600mm, f4, 1/500th. DOF master tells me with this combination I get 1.11ft DOF. He prints it out on the same size paper and hangs it next to the first print.<br /><br />They look the same to the viewers of the prints (Same apparent angle of view, same apparent DOF (~1.1ft), same apparent motion blur (both at 1/500th with the same angle of view)).<br /><br />So when you switch to FX from DX you don't need the same apature lens to get the same looking prints. You can buy a longer, slower lens. So is a DX + shorter but faster lens system more exspensive than an FX + longer but slower lens system?<br /><br />So I compared various "equivilent looking final print" systems based round a D300s and a D700.<br /><br />Remember it was for fun and discussion so there are plenty of compromises and probably disagreement that the set ups produce the same looking print. For example you can't always get everything perfectly matching the maths. E.g. no 450mm f6 lens for FX to match the 300mm f4 lens on DX. But hopefuly looking at the attached table you can get the idea. Add in a few unnoticed typing erros in the table and we could have lot of confusion!<br /><br />So what does it tell us? The interesting one was that if you want 400mm f2.8 at 1/500th at 200 iso and then if you go to f4.2 and 1/500th on the 600mm (to keep the print DOF looking the same) you need iso 450 to keep the exsposure the same.<br>

So does 450 iso on a full frame perform better or worse IQ than 200 iso on a DX? What does shooting at 200 iso gain you on full frame? You have to drop the shutter speed or get a faster lens to use iso 200? <br /><br />Is there a long lens benefit? The system is cheaper with DX although proportionally it becomes less as the lenses get longer. Why not just stick the TC14 on an FX to make it a DX?<br>

<br />Is the FX option of even smaller DOF usefull at super telephoto lengths?<br>

Is there a wide angle benefit? This I think is the main difference (or feature?) of FX. With FX you can run a shallower DOF (as viewed in the finished print) compared to a DX print with the same F-stop setting.<br /><br />Swings and roundabouts:<br />FX = save money on a slower lens but spend more because it is a longer lens<br />FX = need to run at a higher ISO to keep the shutter speed, not an issue as the sensor pixels are bigger<br />FX = lens needs to project a wider image onto sensor but the lens doesn't need such high resolution (lp/mm at sensor) as DX due to larger sensor pixels<br /><br />and visa versa for DX:<br />DX = save money on shorter lens but need a faster lens<br />DX = can run at ISO 200, helps DX as sensor pixels smaller<br />DX = lens needs to project a smaler image onto sensor than FX so you need a higher resolution/sharper lens than FX needs<br /><br />Conclusions? Don't know! Maybe my maths is wrong to get the same looking prints? Just interested in what others see are the pro's and con's of the two different systems.</p><div></div>

[photo5]

<p>Having owned both DX and FX I say its horses for courses, different strokes for different folks. Neither is better than the other, just different. If the D700 had a 100% viewfinder and was the same size/weight at the D300, I would have kept it. But the 90% viewfinder bugged me to no end, and the larger size/weight did too. I loved being able to use my Nikkor manual focus primes on the D700, they performed very well. But the D300 is just a better fit for me cost wise as well as feature wise.</p>

[Andrew Garrard]

<p>Hi Jon. Forgive me if I've only skimmed your table, but I hope I follow your argument (and, give or take rounding, I think I agree with the maths - not that my opinion counts for much).<br />

<br />

Picking on a few points:<br />

<br />

<i>"So does 450 iso on a full frame perform better or worse IQ than 200 iso on a DX?"</i><br />

<br />

For the same pixel count, the FX sensor pixels cover 2.25x the area, so this ought to balance out because the FX sensor sees 2.25x as many photons in the same exposure. In fact, all things are not equal - particularly, there's a fixed amount of "dead" pixel area required for the electronics, so I believe this works out slightly in favour of the FX system - but probably not by much, and not by the amount that sensor technology moves us on. After all, the D3s is significantly better in low light than the D700, yet their sensor site sizes are identical.<br />

<br />

<i>"lens needs to project a wider image onto sensor but the lens doesn't need such high resolution (lp/mm at sensor) as DX due to larger sensor pixels"</i><br />

<br />

I honestly don't know how this works out. It's certainly hard to make fast lenses of decent quality - very few lenses are very sharp above f/2.8, yet it's obviously difficult to produce an ultrawide that's sharp in the corners. I suspect the benefit is with the larger sensor, and that it's easier to make a 200 f/2 sharp at the edges of an FX sensor than it is to make a 135mm f/1.4, if only on the basis that there are lots of 200 f/2 lenses out there but I'm not aware of a 135mm faster than f/1.8.<br />

<br />

In <a href="http://www.photo.net/portraits-and-fashion-photography-forum/00Y1Xm">another thread</a> it was pointed out to me that you can get a 150mm f/2.8 with 5x4 coverage, but not so much a 50mm f/0.7 for 135 format (at least, not of decent quality). Given my low opinion of 50mm lenses used wide open, if a 150mm f/2.8 lacks the optical defects of the 135 fast normal primes it might actually make me interested in normal focal lengths again. Back in the digital world, there's no 35mm lens for DX with the physical aperture of a 50mm f/1.4 (or f/1.2).<br />

<br />

One distinction is that I <i>can</i> put a teleconverter on my FX lens and get something resembling DX coverage. It won't autofocus like a D300 or D7000, and the TC obviously robs a bit of image quality, but if we just consider the sensor, it's an option. There's no "tele-unconverter" that I could put on a DX body.<br />

<br />

I suspect there's a point to be made about sensor resolution and diffraction limits, but I'm not sure I'm qualified to make it.<br />

<br />

If you're always prepared to put up with an effectively slower lens (and by "put up with", I mean "save money and weight in buying"; by "effectively" I mean "compared with the fastest lens of the same effective focal length on FX"), DX has a lot going for it. Otherwise, FX seems to have an advantage in what's available. To get a DX body to behave like an FX with a 400 f/2.8 fitted, you'd need a 267mm f/1.87 lens. Short of rolling out a manual-focus 300mm f/2 and calling it "close enough", there isn't one, and I'll be surprised if there ever is.<br />

<br />

But what do I know?</p>

[mike_halliwell]

<p>You know that 'can-o'-worms' that said "DO NOT OPEN"...welll...<br />The old effect of 2 stops here & there, you could overprocess, knowing you'd underexposed...you get more, maybe too much, contrast or conversely overexposure & underdev...flat negs etc..<br />Now, the amazing products of software like DxO and the like mean high ISO means less 'bad grain' than they used to. It's now the effect of enough light 'in camera' to make the AF module work fast enough that matters and the reduced DOF at low f's....Not the recorded image as such.<br />Pixel density, DX v FX, noise reduction software etc all make so many variables, it's like the old chemistry days of exposure v developer.<br />Equally, I don' t think there is a simple answer. Fast lenses have many well known advantages, one of which is DEFINATELY not price. <br />1 or 2 Stops is easily lost in software but can cost mega $$ in lens...f2.8 v f4 etc..<br />I'll keep this posting in memory!</p>

[eric_arnold]

<p>i dont shoot wildlife or use any lens longer than 300mm, but there are distinct advantages to both formats.</p>

<p>in some ways FF is kind of a canard because you can do almost anything you can do on FX on DX at lighter weight and lower cost. for example, my 50-150 DX is optically close enough to the 70-200 VR II to make comparisons more on the level of pixel-peeping, and also focuses with comparable speed. It doesnt have VR,but its easier to handhold/transport, and plus you dont need VR for action shots.</p>

<p>However... the FX pictures have a different look. i got good results with my DX bodies, but now i find myself wanting to shoot the D3s all the time, unless i need the 1.5x crop. also, the big advantage is in wide-angle lenses and low light. I have a sigma 15-30 which i got for $160 used. its 10mm DX equivalent, so it goes really wide. and on an FX body, the relatively slow aperture (3.5-4.5) is mitigated by the fact i can bump the ISO without losing picture quality. in other words, for most things, i don't need 2.8.</p>

<p>one downside i discovered, though, was the 15-30 doesnt take filters, while my 12-24 tokina does. 15-30 is a pretty useful range on FX, but shooting urban landscapes in bright daylight, it would be nice to be able to use an ND grad for overcast skies. on a recent shoot when faced with this dilemma, i had to switch to the 24-70 for this reason. i didnt have my 12-24 with me as it would have seemed redundant, plus i wanted an ultrawide as opposed to super-wide. so now i'm faced with a quandry: do i pony up for the 16-35 VR or 17-35 (or maybe a W/A prime like the 20/1.8) for wide shots with filters, or do i use the 12-24 with a DX body? i've essentially decided not to get the 14-24 or tokina 16-28 for this reason--they dont take filters, so the advantages over the 15-30 would be minimal--and i'm ruling the sigma 8-16 DX out for this reason as well.</p>

<p>at the end of the day, there's no doubt the FX pics look 'better', but i've printed at 16x20 with DX and pics look pretty good. so the answer is, there's no right answer.</p>

[tom_rittenhouse1]

<p>But! On the other end your get this:<br>

1. Shooter with FX and 12mm lens takes a photo.<br>

2. Shooter with DX and 7.5mm take the same picture.<br>

Oops! #2 can't take that photo, because he does not have a 7.5mm lens.<br>

Comparing apples and oranges, leaves sour lemons. Now which is better my Pentax MX with an 80-200/2.8, or your Hasselblad 500C with a 50/4.0?</p>

 

[Wouter Willemse]

<p>Tom, get the math right, and find out the lens does exist. FX 12mm would be 8mm on DX. And there's the Sigma 8-16 for that (and yes, that is NOT a fisheye). Which happens to have a FX brother in the Sigma 12-24. I think the widest pair for both formats, because otherwise, full frame 12mm lenses are rare. So, your point is a bit moot. The whole "there are no wide angle lenses for APS-C" argument does not make much sense to me; by now there is choice enough and some seriously good lenses too.</p>

<p>As for the 'equivalent' thing...<br>

Personally, I never got the pro-FX argument of a "50mm lens being a 50mm again"; I just stare down the viewfinder to see what it gives me. It connects quick enough to make selection of the right focal length fairly easy; switching from my filmcamera to the DX digital, I have more issues with the different controls than with the difference in how a specific focal length looks and how DoF can be different. I just know how a 35mm prime looks on the film camera and how it does on the DX camera. And I know usually which length I need at a time, regardless of the camera. But maybe I'm not oldschool enough about it.<br>

The whole deal between FX and DX... both means to and end with different strengths and shortcomings. Choose what fits your style and budget best, and enjoy.</p>

[leslie_cheung]

<blockquote>

<p>The whole "there are no wide angle lenses for APS-C" argument does not make much sense to me; by now there is choice enough and some seriously good lenses too.</p>

 

</blockquote>

<p>There are no 17-35 f2.8 equivalent in DX line...There are 12-24mm f4 and 11-16mm f2.8 but neither are equivalent (you lose range or 1 stop). That's not taking in the DOF math. Anyways, I shoot FX because of that and the 85mm f1.4...If they come up with a 11-22 f2.8 and, say, 60mm f1.2, I'll be glad to dump FX *if* I end up saving money... </p>

[eric_arnold]

<p><em>And there's the Sigma 8-16 for that (and yes, that is NOT a fisheye). Which happens to have a FX brother in the Sigma 12-24. I think the widest pair for both formats, because otherwise, full frame 12mm lenses are rare.</em></p>

<p>right, but neither take filters. AFAIK, with W/A on FX, the widest you can go and still use filters is 16mm or 17mm, which is only slightly wider than a 12-24 on DX and not as wide as 10-20 or 10-24...see the paradox?</p>

 

[photo5]

<blockquote>

<p>at the end of the day, there's no doubt the FX pics look 'better'</p>

</blockquote>

<p>Really? Can you provide examples? Certainly if one is shooting at ISO 3200, FX will indeed look "better" than DX. But not at ISO 200. There is no difference between the two formats at ISO 200, in my experience having owned both the D700 and D300. In fact, I believe the D300 can render better fine detail at ISO 200 than the D700, which has a stronger anti-aliasing filter, can.<br>

I really think that people who spent all the money to go FX have to come on to this forum again and again and say how much "better" FX is over DX. It's just a bunch of nonsense! I'd rather take a good photo with DX than a crappy one with FX. The format is meaningless. All FX does is give you the ability to shoot at higher ISOs and get cleaner results while doing so. Otherwise it's pointless to buy one unless you have money to burn.</p>

[Ed_Ingold]

<p>"Better than..." is a subjective judgement, depending on your needs and the particular circumstances. We do know certain facts about the relative performance of DX v FX sensors. Which combination is "better" is another issue altogether.</p>

<p>(1) DX sensors have a smaller field of view than an FX sensor, for the same focal length. This is often expressed as a cropping factor, which has the effect of multiplying the focal length.<br>

(2) The apature (aperture) is not affected by the sensor size.<br>

(3) A DX sensor has the same depth of field as an FX sensor, at the same distance, focal length and aperture.<br>

(4) A DX sensor has a greater depth of field than an FX sensor with the same field of view (e.g., further away or shorter focal length).<br>

(5) An FX sensor with the same number of pixels will have an higher ISO capability at the same noise level. This is affected by the signal processing as much as pixel size, however. For example, my D3 is quieter at ISO 3200 than my D2x at ISO 400, even though the pixels are only 50% larger.<br>

(6) A new D3x costs about the same as my D2x did 4 years ago and my D1x 3 years prior to that. Considering inflation, the price of FX is cheaper than DX for the same class of camera.<br>

(7) My D3 gets at least 600 raw images on a single battery charge, compared to about 150 for my D1x.</p>

<p>So what's better? Cheaper? High ISO? Longer telephoto reach? Better wide angle performance? Better battery life? As always, YMMV ;-)</p>

[Andrew Garrard]

<p>I'll preface this with an agreement that both formats have advantages (not just financial), and that we shouldn't get hung up on them, or get envy over the other sensor size, or buyers' remorse. I'm happy with the lens selection that my D700 allows me to use. Someone with a different selection of needs might want a DX body, and I'm not going to tell them they're wrong. Someone might really need micro 4/3, or medium format sensors, or a large format scanning back, or to scan a 20x16 exposure, and I can imagine how they're all justifiable, if not necessarily for me. If they weren't all <i>sometimes</i> for me, I'd not carry a compact camera, a D700 and a Pentax 645, and have my eye on a 5x4. Each in their place.<br />

<br />

Just to say:</p>

 

<blockquote>(3) A DX sensor has the same depth of field as an FX sensor, at the same distance, focal length and aperture.</blockquote>

 

<p>That statement is entirely true, but also utterly misleading (not that it necessarily matters in this context). Nobody cares (usually) about the depth of field of a sensor - what matters it he depth of field of a final image. If you have to enlarge the output of a DX and FX sensor by different amounts to get images of the same size to compare, this introduces a change in depth of field. Just being pedantic, in case someone picks up on this claim.</p>

 

<blockquote>For example, my D3 is quieter at ISO 3200 than my D2x at ISO 400, even though the pixels are only 50% larger.</blockquote>

 

<p>Trusting DPReview's claims, the D2x had 3.3MP per square cm, vs 1.4MP for the D3. Don't forget: 2.25 times the sensor area. The D3 is <i>still</i> better than that (it blows my 6MP Eos 300D out of the water as well, and the pixel sizes are far more comparable), but I'm just checking the maths. :-)<br />

<br />

Enjoy the canned worms, everyone.</p>

[Ed_Ingold]

<p>What! What! A scholar lurks amongst us ;-)</p>

<p>The pixels in a D2x are spaced at 6 microns, compared to 9 microns in the D3. By diameter, the factor is 1.5, but by area 2.25x. The difference in ISO capability can't be explained by the pixel size alone.</p>

[Ed_Ingold]

<p>Lens prices are not proportional to focal length, there are many factors. At the time, my 17-35/2.8 cost less than an 18/2.8, yet three times as much as a 20/2.8, somewhat more than a 300/4 and about the same as a 28-70/2.8 or 80-200/2.8 AFS (all of which I've managed to acquire).</p>

[Wouter Willemse]

<p>Eric, I do not see how we disagree (your 6:31 pm post) ? The paradox being that you can have 10mm on DX with filter, but no 15mm on FX with filter? I did not say anything about filter usage anyway, my point was more the claim that there was no DX equivalent to 12mm wide on FX. There is, and both for DX and FX, the available options to go that insanely wide are limited (in fact, I only know these 2 Sigma's).<br>

Leslie, true, there is no lens-for-lens equivalent for each lens, and sure on a personal level, everybody can have reasons to prefer one over the other. I'm not arguing against that.</p>

[Andrew Garrard]

<p>Edward: I agree, technology generation matters too. Compare the high ISO performance (by which I mean 400) of a DCS 14n, which I'm considering trying to pick up as a back-up for my D700, to the D3s. There's very little pixel size difference, but several years of advances. Still, if we're comparing DX and FX, we shouldn't get distracted with technology generations. I suspect there's still a difference in favour of FX sensitivity even so, but not by much.<br />

<br />

Lens prices - market forces aside - have a lot to do with the amount of glass, and the size of a single element that has to be perfect. A 14-24 is pricey, but the front element is huge. An 18-200 is reasonably expensive because it has so many elements. The (fast) supertelephotos cost a fortune because of the big front element(s). It shouldn't be all that expensive to make a 600mm f/8, but not many would want one.<br />

<br />

More a geek than a scholar, though. :-)</p>

[michael_bradtke]

<p>Andrew<br>

If you can find one get a Pro 14 NX. The built in Pocket wizards come in handy and the buffer has been upgraded.<br>

I have one and love it for studio work. I find it to be very sharp and to have very good Dynamic range</p>

[michael_bradtke]

<p>Double post sorry</p>

[eric_arnold]

<p><em>Eric, I do not see how we disagree (your 6:31 pm post) ? The paradox being that you can have 10mm on DX with filter, but no 15mm on FX with filter?</em></p>

<p>right. that's a paradox, because FX is "better" with wide-angle lenses. but is it really better, if the widest you can go (and use filters) is 16mm?</p>

<p>i wasn't disagreeing with you btw, i was just stating my own observations from using both formats. it was kind of irksome to be in a situation where i wanted to go wide, but i also would have liked to use a filter--shooting bright skies during the middle of the day. my only options were to forgo the filter (and adjust brightness in post-), switch to a less-wide lens which could take filters, or come back later in the day when the light was better (which often isnt an option). i had the d300s with me too, but not the 12-24 as taking both FX and DX UWAS would have seemed overly redundant.</p>

<p>to some degree, i think the sigma 8-16 has changed the game. prior to its release, the only way go go "insanely" wide was FX. now that you can do that on DX, one has to question whether FX is even necessary. for the price of the 14-24, one could conceivably get both the 8-16 and the 10-20, and thus have the option of filters or no filters. of course, the 14-24 is 2.8 and is the cat's meow of w/a optics, but the 8-16 seems pretty dang good from what i've seen, if you can live with the speed.</p>

<p> </p><div></div>

[Andrew Garrard]

<p>Thanks, Michael - I'll keep an eye out (after a few pay cheques!)<br />

<br />

Eric - I agree that the ultrawide DC Sigma is an interesting optic. One reason I moved to full frame a few years ago was the desire to use ultrawides; the 14-24 may (I assume) be "better", but there's no doubt that the existence of an ultrawide for DX bodies opens the format to more people. For me there were other reasons to want FX as well, but I can't deny that this was one of them. In contrast, replacing my Canon EF 70-300 IS with a Sigma 150-500, to keep a similar field of view when I moved to FX (and Nikon), really brought home the size difference in formats. The 70-300 doesn't scare people. Most of my friends haven't even seen my 500 f/4 yet - partly because I'm not really on for hand-holding it.</p>

[eric_arnold]

<p>i moved to FX because i really wanted the better high-ISO performance. also because i had a 15mm fisheye which was only semi-fishy on DX. i really like shooting with wide lenses, but now that the 8-16 is out, the wider-is-better-on-FX part of it is kind of a gotcha. i got a used 15-30 for a great price--$160--so my buy-in to FX W/A wasn't that bad. last week was my first time really putting it through its paces on FX. it's optically very comparable to my tokina 12-24, just a bit less contrasty stopped down to f/8-11 and just a bit better wide open, perhaps. having 15mm on FX felt pretty wide, so i was happy with that. overall, it's a decent range, and i can't complain about the price. but i immediately ran into a situation where being able to use filters would have been nice. so now i'm stuck. i dont really want to shell out the cash for a 17-35 or 16-35 VR, but it looks like i'll have to, unless i want to restrict my UWA shooting on FX to nighttime shots or shots without daytime sky in them. i'm definitely passing on the 14-24 and tokina 16-28 because neither takes filters. i may just get a 20/1.8 while i mull it over, which would at least give me a little bit wider than the 24-70 with filter capabilities--i like the idea of fast primes in any event--but i wouldnt say there's a huge advantage over DX in this regard so far, at least not as huge as i was led to believe. who knows, maybe i'll print at 20x30 and that will justify all these added expenses. or not.</p>

<p>ps--what's wrong with scaring people with your massive, obtrusive lens? you should try it for people shots at a gun control rally, just to see what response you get ;)</p>

<p> </p>

[eric_arnold]

<p><em>All FX does is give you the ability to shoot at higher ISOs and get cleaner results while doing so. Otherwise it's pointless to buy one unless you have money to burn.</em></p>

<p>Dave, i don't totally disagree with you. maybe i should have said the FX shots look different. i havent really printed any large prints on FX yet so i can't say for sure. there's definitely a difference as far as pixel density which i find visually-appealing, but it's not like all of a sudden all my DX camera shots are garbage... i don't know, i'm still getting used to the D3s. i dont think it's completely pointless, but it may well be a waste of money for some people.</p>

<p>i'll admit, with a D3s, sometimes i feel a bit ashamed shooting at base ISO or 400, because i'm not using FX to its full capability. i'll get over it, i'm sure. OTOH, the other day i shot candids in a dimly lit music studio at ISO 8000, which looked like 3200 on the d300. that's one reason i went D3s rather than d700, as the d700 and d300 are very similar (save for the ISO performance and the fact that you cant use Dx lenses on a d700 except in the worthless 5mp crop mode). what i really like about the D3s is the ability to adapt to any photographic situation which presents itself, which works for me as a PJ. the integrated grip also works better on a tripod, and the AF is second to none. what i dont like so much are the added weight--it's too big for a lot of bags--and having to buy all-new lenses, plus its not nearly as convenient. right now i'm mainly shooting with either the D3s or the d90, and reserving the D300s for when i need two bodies and/or more reach than i would get on the D3s. as for the cost, well, the money's already been spent, so i'll just have to recoup that down the line... i'll say this: having a D3s didnt make me a better photographer, but it does make me take myself more seriously as a photographer...YMMV.</p>

<p> </p>

[ilkka_nissila]

<p><em>All FX does is give you the ability to shoot at higher ISOs and get cleaner results while doing so. Otherwise it's pointless to buy one unless you have money to burn.</em></p>

<p>Are you trying to be provocative? There are of course many other reasons to use FX. The images from FX cameras are more editable (because the number of photons recorded is twice as many, leading to better tonality). There are no DX equivalents to the 24 PC-E or 24/1.4. Generally, image definition with wide angles and short to medium FL fast lenses is from subtly better to much better with FX (lower spatial frequencies correspond to higher detail contrast and because the image area is bigger, you are looking at smaller frequencies for equivalent content). Lenses designed for specific purposes have their intended angle of view on FX and produce closer to optimal image quality since half of the image area isn't chopped off (i.e. 85/1.4 for portraits etc.) There's a bigger viewfinder so you can see things clearly and don't have to put so much on faith that the facial expressions and focus are allright. Small autofocus inaccuracies (e.g. with 180/2.8) have less effect on the final result since the area is bigger. And finally, if you need it, there is the potential to 24 MP today or up to something like 40 MP in a few years whereas there isn't much more that can be pulled off out of current lenses with DX sensors than today's cameras already do. Personally I find FX more forgiving; it's easier to get consistently high quality.</p>

[jon_savage]

<p>Eric, (trying not to be provocative!) you mention "<em>D3s ... in a dimly lit music studio at ISO 8000, which looked like 3200 on the d300</em>". I think we should expect FX at 8000 to look like DX at 3200.</p>

<p>Assume you match the field of view, depth of field and shutter speed as shown through the DOF Master numbers (see my original post). To get a matching printed image (i.e. both systems give you the same information in the print) the iso for FX needs to be 2.25 x the iso of DX. So DX iso 200 equates to 2.25x200 (iso450), or 3200 equates to 7200. As the FX sensor area is bigger but with the same number of pixels I can see why the performance should be equal in these conditions. But when both are run at base 200 iso the FX should be better.</p>

<p>I was struggling to see what FX gets you but I think Ilkka's comments are making it clearer to me. FX comes with a sensor that when run at its base iso (therefor most optimum?) you should have better IQ (tonality?). </p>

<p>Also it lets you run at 2.25 the iso so getting your FX low light performance equal the DX normal light performance. To me it felt like there is a" free lunch" somewhere but I think the trade off might be the field of view in the final printed image. See attached image, numbers appear to check out OK with the online DOF master.</p>

<p>Also as Ilkka say's there are many more lenses specifically optimised for full frame. And the clearer viewfinder.</p>

<p>Ilkka, Could you explain the "<em>Small autofocus inaccuracies (e.g. with 180/2.8) have less effect on the final result since the area is bigge</em>r" comment?</p>

<p>Just thoughts</p><div></div>

[eric_arnold]

<p><em>I think we should expect FX at 8000 to look like DX at 3200.</em></p>

<p>well, actually, that's currently only possible on a D3s. the d700 isn't quite as good at 6400 and above.</p>

<p><em>FX comes with a sensor that when run at its base iso (therefor most optimum?) you should have better IQ (tonality?).</em></p>

<p>maybe that's the word i was looking for: tonality. again, IQ on a d300 or d300s is very good. but FX is better. the question is, though, when and how does it matter? printing large, certainly. DoF, yup. high iSO? yup. but the trade off is that once you're in that lane, you can't really cheap it out--FX demands good glass, and you run into annoying little niggles like the UWA filter issue.</p>

<p>however, advances in technology may make this a moot point eventually. the d7000 is already creeping up on FX territory in some key areas, although i'm a little concerned about 16mp making mincemeat out of some lenses which were decent at 6, 10, or 12 mp.</p>

<p><em>as Ilkka say's there are many more lenses specifically optimised for full frame</em></p>

<p>well, yes and no. we need to differentiate here between full-frame (e.g. film and FX digital) and FX (FF digital). some of the film-era nikon primes just dont do well on digital (flare, CA, etc.). and FX has only been around for 3 years in nikon-land. so any lens produced before that was <em>not</em> optimized for FX, the obvious example being the 70-200 VRI, which was great on DX but had to be updated for FX. OTOH, we run into some DX-only lenses which end up being overpriced in their market segment, like the 17-55, which made a lot more sense before it had serious competitors at fractions of the cost.</p>

<p>also, using FF lenses on DX has advantages in terms of edge performance at wide apertures, since you're using the center part of the frame. so i guess the answer is, "it all depends." was that vague and non-provocative enough?</p>

<p> </p>