Digital Technology lenses/APS-C size optimized, meaning?

MBasile · May 21, 2009

Can someone please explain what "digital technology" lenses are? Sony is branding all of their newer lenses as DT lenses, meaning they are optimized for the APS-C sized sensors, but what does this mean? What is the advantage?

Reason I ask is because they have a 50mm f/1.4 prime lens, as well as are introducing a 50mm f/1.8 DT prime lens for less than half the price and I'm wondering which path to take...

Thanks in advance!

photogincollege · May 21, 2009

Well basically, those lenses are designed with cameras that have a smaller then full frame sensor in mind. IE 90% of DSLR's. They will still work on a full frame camera, but it will crop the image down quite a bit.

benhasajeep · May 21, 2009

(Long version) What he said above plus they also put additional coatings on the lens to reduce reflection off the sensors. Most of the manufacturers now add these coatings. Each has their own fancy term for it.

(Short version) they have invented a term for sales literature that basically means their lenses will work with their cameras.

As for the 50 1.4 vs 1.8DT lens. It all deppends on if you want to move up later on to a full frame DSLR. The 50 1.4 would be the better lens for quality and usability if in the future you decide to move up to their full frame model of camera. The 50 f/1.8 will only be "FULLY" useable on APS-C cameras (on a full frame they will cause vignetting in at least the corners) or the camera may automatically drop into a APS-C mode where it will only use the center part of its big sensor, basically a mode where it changes to an APS-C camera (you would not get the full mega pixels of the sensor!).

Garbz · May 21, 2009

(Real Version). Not to go against benhasajeep since much of it is right, (except for the reflection off the sensor bit, that is rubbish and non-DX equivalent lenses have identical coatings on them anyway even from the film era), but there are many benefits.

APS-C cameras have smaller sensors, that much is obvious by now, but the question is why cast and waste so much light on a sensor when 95% of the users will probably never upgrade to a full frame format camera like the Sony Alpha 900 or the Nikon D700, or Canon 5D MkII. For these 95% of users the full frame lenses are a waste.

Well designed APS-C cameras will be smaller, and lighter, not to mention that since they are modern they will be guaranteed to be fully compatible with the fancy gear inside your camera that relies on all the digital information exchanged between the lens and the camera. If you can't ever see yourself owning a $4000 camera then I suggest invest in these types of lenses.

benhasajeep · May 21, 2009

Feature 4: Lens coating optimized for use with digital SLR cameras
The EF50mm f/1.2L USM has element curvature and coating optimized for use with digital SLR cameras. It successfully realizes both good color balance and minimization of ghost and flare attributable to surface reflections from the digital imaging element. Not an APS-C only lens but they do have coatings for that. And I have in the past seen it referenced in advertisements for several lenses.

Canon also list that tech spec for the 18-55 and 55-250 lenses which are APS-C only.

Maybe its an advertising gimmic or not. But it is specifically mentioned for reflection off sensors!

skieur · May 21, 2009

It should also be pointed out that beyond price, the disadvantage to full frame cameras is that they require larger lenses for the telephoto end and a tripod becomes more necessary.

In megapixel terms as well, a 12meg crop body and a 24meg full frame sounds like double the resolution but it really means a 20% better resolution which may not be very noticeable when contrast, colour, exposure and other factors are taken into account.

skieur

MBasile · May 21, 2009

Alright, thanks for the replies guys!

Garbz · May 21, 2009

benhasajeep said:
Maybe its an advertising gimmic or not. But it is specifically mentioned for reflection off sensors!

There is definitely more truth to the marketing gimmic side of things. But there are a few points to note:

a) I mean reflections off the sensors ARE there. But the whole point of the low pass filter if you ever look at one close up is that they only reflect infra-red light. Much the same as the goggles I had to wear in the lab they reflect so little visible light that even in extreme circumstances it's hard do see your own reflection.

b) These coatings would make a difference for infrared photos only, where the the reflection is visible as a hot spot, roughly in the middle third of the frame.

c) When I look into all of my lenses, most of which are designed for film bodies of the 90s because I am cheap, they all already have coatings on the back elements to reduce this kind of reflection and incidentally I do not get hotspots on any of them, unlike a friend of mine who's Canon 350D kit lens (not sure which one) makes infrared photography unusable.

The sad reality is that the word digital sells cameras these days. Just look at Hoya's website. Their fancy pro level filters are "Digital Multi Coat", which as far as I can see seem to work slightly WORSE than their "Super Hoya Multi Coat" but have a $50 markup.