FX Primes on DX bodies

WestEndFoto

Light gathering ability will be the crop factor squared. I can't view his video on my phone though, so I can't comment.

Ironheart

But the EV would be the same. e.g. If the scene were a bright sunny day, the "sunny 16" rule would still apply: f/16 1/100th ISO 100

heartyfisher

Cant comment easily (as i still cant get access to the forum cant view the forum from my pc only access is via my phone which does not have a lot of data) yes tony keeps saying that multiply aperture by 1.5 thing which is mostly wrong and partly right. Luckily he is the only one who says it. It is only valid for dof.. not amount of light.

JonMcGuffin

Cant comment easily (as i still cant get access to the forum cant view the forum from my pc only access is via my phone which does not have a lot of data) yes tony keeps saying that multiply aperture by 1.5 thing which is mostly wrong and partly right. Luckily he is the only one who says it. It is only valid for dof.. not amount of light.

This is in fact correct. To equalize DOF, you do need to make the multiplication, but a 1.2 Lens on DX will gather the same amount of light for making an exposure as 1.2 on FX. He is saying that's not the case.

Also note, his entire premise of that detailed (and very well done) video is that FX lenses *DO NOT* perform better on DX bodies and that it's quite opposite. He is saying by DX lenses for DX bodies and FX lenses for FX bodies. His only caveat is when it comes to long telephone lenses in "wildlife" scenarios.

The notion that because you're only taking an image in from the sweet spot of an FX lens when mounted on a DX body is being challenged by him. I like and trust Tony very much, but I think he has this data inaccurately. I'd just like to know what others here think of this.

Jon

haroldp

This is a two edge sword.
It is true that only taking an image in from the sweet spot of an FX lens when mounted on a DX body, but the importance of it depends on how good the respective FX and DX lenses are.

It is also true that all other thongs being equal (size, cost, weight etc.) it is easier to correct a l;ens fir a smaller image circle since 'edge' corrections may degrade center performance, requiring mor or better (ie exotic) glass to compensate.

That is why a nikon 35mm 1.8 FX lens is almost 3 times the price of a 35mm DX lens and not significantly better in the DX image circle.

For 'longer' lenses this seems to matter less.

The big variable is price / cost. The Leica 50mm f2 apo summicron is corrected to military / industrial standards across the frame, wide open, but costs $ 8,000 for a 50/2, manual everything. I do not, and probably will never have one.

... H

BVS

This is in fact correct. To equalize DOF, you do need to make the multiplication, but a 1.2 Lens on DX will gather the same amount of light for making an exposure as 1.2 on FX. He is saying that's not the case.

I don't think he explained it well, but he might have just been saying that an FX lens takes in more 'overall' light than an equivalent DX lens since it needs to produce a larger image circle while still maintaining exposure.

Also note, his entire premise of that detailed (and very well done) video is that FX lenses *DO NOT* perform better on DX bodies and that it's quite opposite. He is saying by DX lenses for DX bodies and FX lenses for FX bodies. His only caveat is when it comes to long telephone lenses in "wildlife" scenarios.

The notion that because you're only taking an image in from the sweet spot of an FX lens when mounted on a DX body is being challenged by him. I like and trust Tony very much, but I think he has this data inaccurately. I'd just like to know what others here think of this.

Looking at DXO's numbers (which is what he's using in the video), putting an FX lens on an FX body typically does produce sharper results than putting the same FX lens on a DX body.

On the other hand comparing putting an FX lens on a DX body to putting a similar DX lens on a DX body probably really depends on the particular lenses chosen. Unfortunately, there's often no choice but to use FX lenses though since Nikon hasn't blessed us with many DX primes, and the ones we do have are of somewhat lesser quality than their FX brethren, so a true apples to apples comparison is difficult. However, the available FX lenses do tend to produce sharper images on DX bodies than the available DX lenses on DX bodies based on the numbers, so I think he's somewhat wrong in this case. Hopefully some quality new DX lenses like the 16-80 will help close the gap.

sevencrossing

Given there are only 4 nikon DX Primes and 48 FX Primes
it's a bit academic

Ironheart

Given there are only 4 nikon DX Primes and 48 FX Primes
it's a bit academic

Amen )

esquilo

As I see it, there is no reason not to use FX primes on a DX body. The only area when you really need a DX-lens is for wide-angles.

The second lens i bought for my camera (then D5100) was the Nikon 35 mm f/1.8 DX. It was sharp all right, and very affordable. However, 35 mm was just not right for me. I needed something a little wider.

So I sold it and got the Sigma 30 mm f/1.4 EX DC HSM. That one really sucked! It was tack sharp in the center but the corners would never get sharp no matter how much i stopped it down.

Running out of options regarding DX primes I decided to try the Nikon 28 mm f/1.8. That one was perfect! The focal length of 28 mm equals the diagonal of the APS-C sensor which makes it ideal as a normal lens. It is sharp all over (very little softness in the corners at f/1.8 and f/2). It has some field curvature, but not much. Also it takes the same 67 mm filters as my 16-85 and 70-300.

KnockKnock

In a similar vein, I'm very tempted by the new 24mm f/1.8 for DX use with possible forward thinking to FX.

NSXTypeR

My cousin used the the Sigma 30mm 1.4 for a while on his Canon XSi, it was terrible. Photos weren't sharp wide open, so it was pretty useless. I don't think he used it all that much and he ended up trading it in, practically unused.

I'd like to try the 24mm or 28mm on DX, but I'm trying to decide to get a 70-300mm instead or a wide prime. The wider prime is about another $200 more than the 70-300mm.

spraynpray

@NSXTypeR - Probably best you think of the 70-300VR as a 70-250 as my copy wasn't sharp enough above that. I know it is a different order of cost, but the 80-400G is a much better bet,

NSXTypeR

Yeah, I understand that, but the 80-400mm is like 4x the price of the 70-300mm. My budget is limited, $1000 is about the upper limit of what I'm willing to spend.

heartyfisher

The Old Sigma 30mm had some "issues" .. there is a new 30mm sigma ART lense and that is much better. there are a few nice reviews on youtube etc.. however it looks like most people prefer the 18-35 1.8 zoom over the 30mm 1.4 ART. even if its abit heavier and more expensive.

NSXTypeR

The Old Sigma 30mm had some "issues" .. there is a new 30mm sigma ART lense and that is much better. there are a few nice reviews on youtube etc.. however it looks like most people prefer the 18-35 1.8 zoom over the 30mm 1.4 ART. even if its abit heavier and more expensive.

Didn't know they came out with a 30mm ART. For DX users though, you're right, when there's an 18-35mm zoom, there's no reason to buy a 30mm prime.

heartyfisher

The Old Sigma 30mm had some "issues" .. there is a new 30mm sigma ART lense and that is much better. there are a few nice reviews on youtube etc.. however it looks like most people prefer the 18-35 1.8 zoom over the 30mm 1.4 ART. even if its abit heavier and more expensive.

Didn't know they came out with a 30mm ART. For DX users though, you're right, when there's an 18-35mm zoom, there's no reason to buy a 30mm prime.

It was one of those "quiet" releases.. ie basically fixes it to be what it really should have been. so Its not as spectacular as the other "ART" lenses but its "not bad". quite good really if you want a prime normal 30mm F1.4.

esquilo

The Old Sigma 30mm had some "issues" .. there is a new 30mm sigma ART lense and that is much better. there are a few nice reviews on youtube etc.. however it looks like most people prefer the 18-35 1.8 zoom over the 30mm 1.4 ART. even if its abit heavier and more expensive.

I considered the Sigma 18-35 f/1.8 before buying the Nikon 28 mm, but I refrained because of the price and size. The 18-35 is darn long compared to a prime. It would take up as much space in my camera bag as the Nikon 28 and 50 together.