10 replies to this topic

[OTRTexan]

I'm curious to hear your opinions on the subject of buying a DX body for the supposed extra reach with lenses. This has been a curiosity for me for awhile now and really fail to understand people's reasoning. Perhaps I'm missing something.

In any photography group, people ask advice about which body to buy. Heck when I was deciding between the 750 and 810, I was here asking opinions. Inevitably you'll see the comment made that they should buy a DX body for extra reach. Now in my eyes, and from my experience with my DX to FX move, this magical extra reach is an illusion, and only has any effect on shutter speed requirements at the long end of a super tele. I can take the same shot, at the same actual focal length, on a DX and FX body. Using the FX file, I can crop to the same image and get the same "reach". However... You can not take the DX image and back it out to replicate the FX image.

Now bear in mind I'm strictly talking about the "reach factor" here and comparing models as close to each other as possible. I fully understand why a sports shooter would choose the D500 over the 750 or 810 as there are other factors involved. I don't however understand people suggesting a 7200 over the 750 or 810, when cost is not an issue, to get extra reach.

Am I missing something?




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[dcbear78]

As much as you can crop I find you do lose quality doing so. Also not everyone has a 36mp file to crop. Cropping a 20mp or 24mp file is going to have severe detrimental affects.

Additionally the image fills the viewfinder which aids composition.

This is much like saying why would anyone bother with an expensive 300mm or 400mm f2.8 lens when you can crop a 200mm image.

[Merco_61]

This depends on if you need more than 15 MP or not. It also depends on if your lens outresolves the D810 or not. 24 MP on DX is a challenge for any lens as most non-pro and some of the pro zooms are perceptibly softer on the D810 than the D750. This turns the "DX reach" into empty magnification.

Some pro zooms like the 70-200/2.8 and the 200-400/4 have resolution enough for the virtual 57 MP on FX the 7200 sensor would provide if one cut a FX wafer from the same matrix. These lenses gain from the use of a DX body instead of cropping from a high resolution FX sensor. I can't think of any tele prime that don't benefit from a DX body rather than cropping from FX.

[dem]

Interesting. Say we compare a D300 (12 Mpx APS-C) to a D810 (36 Mpx full frame) with the same lens attached. As the D810 gives a 36/1.5/1.5 = 16 Mpx DX-sized image, I would expect it to outperform the D300 with any lens. Is this not the case?

[Merco_61]

Not with any lens. The old 70-300 non-ED for example was barely adequate on the D300 and is mushy on the D810. It is still a matter of empty magnification vs optical resolution that outperforms the sensor's, only the other way around and much fewer problematic lenses.

[Jerry_]

James you are correct in saying that there is no extra reach - a 100mm focal length will be a 100mm focal length both on FX and DX.

However, as mentioned both by Peter and dem, if I compare a capture taken on a 24MP FX sensor (let's say a D750 or D610) and the same capture taken from the same distance (and obviously a lens set to the same focal length) on a DX body, you have a cropping factor of 1,5 due to the smaller size of the sensor.

Considering that a capture is a surface, this 1,5 crop factor applies to both dimensions (large and length), thus becoming it exponential by 2. [for those who like a bit of math the crop factor of 1.5 times smaller can be expressed as having it a size of 2/3 (the inverse of 3/2=1.5). Applying an exponential factor of 2 turns the 2/3 into 2^2/3^2 or 2*2/3*3 = 4/9 = 0,44]
So the resulting sensor SURFACE of a DX sensor is about 44% of an FX sensor.

Still, in our example D750 vs D7200, both have the same number of megapixels (24MP).

Thus, if I take the capture on an FX body I will have initially 24MP and when I crop it to the same FIELD OF VIEW then I would get on a DX sensor, there would be merely (24*0,44=)10,6MP left in the cropped zone; whereas the DX sensor would provide the same (now uncropped) zone with a detail of 24MP.

An interesting article to read on the angle of view, which also considers the crop factor, without being to technical:
http://lovedigitalph.../angle-of-view/

But this is just about "reach", there will be number of other factors to take into account when deciding about FX vs DX.

[Brian]

If you are going to crop the image anyway, using a crop-sensor saves work and is housed in a small, lighter, less expensive camera.

 

I put the 300/4.5 on the Df today to shoot pictures of fox pups in the backyard, could get to 50ft of them. I thought about putting it on the Olympus u43 and shooting from the Deck on a tripod, about twice the distance. Went with the Df for it's improved High-ISO, meaning I could shoot hand-held. Big pixels on the Df gets much better high-ISO performance compared with the Olympus.

[TBonz]

Always nice to be able to fill the frame and do little if any cropping, but you would be surprised at how nice some of those cropped images - even on low megapixel bodies.  But, it also depends on what your are shooting and the lighting conditions...I know I've gotten some "great" images at high ISO that I've had to crop quite a bit...they look good and will print fine, but I wouldn't want them enlarged to 11x14 or bigger as the grain would be too obvious...

 

That happens in football on a long play sometimes...or an outfielder in baseball...I'll try it anyway - sometimes it works and sometimes it doesn't make the cut but I'd rather try and fail but at least have the chance at a nice image...At some point - maybe football season next fall - I think I might rent a D500 and throw it on my 200-400 to give me a good comparison...My goal is to eventually add a 3rd body and the D500 is what I'm leaning towards right now...

 

Of course, I may hate it if, as I expect, it gives me less grain than my D4 bodies!

[Merco_61]

Tom, you definitely have glass that is good enough to make the D500 sing. With good enough glass, the DX reach advantage is very real.

[TBonz]

Peter - I agree completely...and that is one of the reasons I chose the 200-400 rather than the primes...still want to get one of the primes at some point - probably the 300 and a used one at that - since the fields here don't appear to be as nicely lit as the fields where I used to shoot.  The fields at the high school my boys attended probably had the best lighting of any of the schools I've ever been to!  

 

Folks in the US would assume National Football League when hearing the initials NFL...I was shooting next to a sports photographer for the Washington Post.  I'd shot with him before and we had chatted a few times...we were shooting a high school football game on a very poorly lit field and between plays, he pointed at the lights, looked at me and said "NFL Quality".  I laughed and he said, "No, I'm serious, there is No Flipping Light quality!"

 

The 200-400 would be nice to try with the crop body as a 300 or 400 with the crop would just be too much reach at times!  I shot a few games with my D600 and rented 300 and 400 lenses - football, lacrosse and baseball.  They are amazing lenses but I had to be sure I was in the right place to shoot - especially with the 400 and be sure I had the 70-200 on the other body for when they got too close...I can imagine that a crop body would make that all the more difficult!

[Kenafein]

I think the D810 was the best, affordable, birding camera Nikon has made until the D500 came out.  I have never even touched a D4 or 5 and those are in a completely different class. The advantages for DX cameras, for birds, are the faster shutter speed and the greater pixel density.  On most birding shots you're going to crop anyways.  The D810 can be shot in crop mode, but in a DX you know what you're shooting will be in the frame, and the D810 can't shoot at 7-10 FPS.  Still, the D810 blows the D7200 out of the water.  The buffer and AF alone are worth the loss in pixel density.  Nikon crippled their recent DX offerings until the D500, especially with the buffer.  As for the reach aspect, it's mostly angle of view.  It only provides benefit with a very dense sensor, which DX cameras have, but the D810 is a good middle ground.