stangro
New member
Discounting saving file space and camera internal memory writing speed, is there any reason to use Nikon's DX mode over slapping on a teleconverter on current mirrorless cameras? Particularly any autofocus and/or IQ benefits?
Teleconverter versus DX mode for mirrorless camera
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Krish
Active member
You're assuming that a "slapping on a teleconverter" and DX mode are an either/or usage. They aren't.
I sometimes use both together - that is the teleconverter + DX mode - to get a bigger picture in the frame when I'm not physically close enough
When you pixel-peep there will be an image quality reduction with the teleconverter attached. DX mode gives you a smaller (megapixel) image size.
Those are the disadvantages.
That said, in real world practical useage of the Z8 and Z9 cameras, those disadvantage are so small that you would hardly notice any difference in image quality.
For autofocus, if your light is good and if/when the subject is too small in the frame it is better to switch to DX mode to get a faster/surer focus lock. Or use a teleconverter. Or both.
In low light its usually better to have the teleconverter off. With or without the DX mode.
SCoombs
Well-known member
The key factor here is that DX mode doesn't actually give more zoom - it just crops an image in camera in a way that could be accomplished exactly the same by cropping it on the computer later on. I do have a button programmed to swap into DX mode so I do think it's very useful, but I know it isn't giving me more detail or a sharper image than I would have if I'd just left it in FX mode and cropped later.
On the other hand, teleconverters do reduce the quality of image that a lens can produce, but in exchange for this tradeoff they do give you an actual advantage in more magnification, meaning you can get that larger image with more pixels. If the reduction in image quality is not too much, you'll get a more detailed image than you would from simply cropping with DX mode. If the reduction in image quality is too much, you'll get a more detailed image that is of lower quality, so it may be worse than just cropping. The key is that a teleconverter can yield a more detailed image over the bare lens in FX mode even if sometimes it doesn't, while DX mode can never yield a more detailed image.
On the other hand, teleconverters do reduce the quality of image that a lens can produce, but in exchange for this tradeoff they do give you an actual advantage in more magnification, meaning you can get that larger image with more pixels. If the reduction in image quality is not too much, you'll get a more detailed image than you would from simply cropping with DX mode. If the reduction in image quality is too much, you'll get a more detailed image that is of lower quality, so it may be worse than just cropping. The key is that a teleconverter can yield a more detailed image over the bare lens in FX mode even if sometimes it doesn't, while DX mode can never yield a more detailed image.
Many claim that DX allows the AF to work better on things the camera is programmed to recognize like birds.
There are endless discussions here and elsewhere on line as to which produces better IQ. As @Nimi mentioned on Z8/9 DX mode does benefit AF challenging conditions. Not sure about any of the other bodies. I've tested this a good bit and the AF will often find an animal's eye in DX mode when it unable to do so in FX mode.
It took me time as well to wrap my brain around TC’s and DX.
Looking at a TC, It’s easy to see what it does. Its cutting out the inner circle of the image, then magnifying it optically to become bigger to fill the sensor.
It’s losing light, because it has just cut away the outer circle. The inner cut out circle have gathered light and resolve details which is now being spread out to fill up the frame.
The image gets softer, the loss of light is real.
DX does the same cut out, but its not upscaling it to fill the frame like a TC, it’s leaving it as is, a cut out. And a reduced resolution file.
The camera however, does spread out the cut out to fill the frame in the EVF, otherwise the EVF/Back screen, would have black stripes around the frame.
Then there is the topic about cropping or use a TC, which is a different discussion.
Looking at a TC, It’s easy to see what it does. Its cutting out the inner circle of the image, then magnifying it optically to become bigger to fill the sensor.
It’s losing light, because it has just cut away the outer circle. The inner cut out circle have gathered light and resolve details which is now being spread out to fill up the frame.
The image gets softer, the loss of light is real.
DX does the same cut out, but its not upscaling it to fill the frame like a TC, it’s leaving it as is, a cut out. And a reduced resolution file.
The camera however, does spread out the cut out to fill the frame in the EVF, otherwise the EVF/Back screen, would have black stripes around the frame.
Then there is the topic about cropping or use a TC, which is a different discussion.
arbitrage
Well-known member
On Nikon and Canon cameras using DX improves BEAF. But so would adding a TC. Anything to enlarge the subject presented to the CPU.
The head scratcher is that on Sony the BEAF actually seems to get worse in DX mode. I still can’t figure out why.
The head scratcher is that on Sony the BEAF actually seems to get worse in DX mode. I still can’t figure out why.
Different viewpoint…there might be a difference at pixel peeping in Lr…but in a most cases (at least with Nikon and not including the $$$ exotic lenses) it will be slight and at least in my testing is usually more ‘different’ than ‘better/worse’ when looking at sharpness. Bokeh differs but that’s focal length and aperture related. However…when downsampled for screen output most of whatever differences exist at 1:1 disappear at least in my testing. There is more difference with the 2.0 than the 1.4 but again it isn’t bad, just not quite as good but still more than good enough for most people. The TC is IMo a better choice than just DX because it puts more pixels on target and thus more small detail…i tend to shoot in FX and crop in post if i still need more subject size in the frame. Bottom line for me is I will use the 1.4 without hesitation and will use the 2.0 with a little but the 2 stop loss means in weak light it’s less likely to be used and I would use the 1.4 and crop a bit or just have environmental instead or portrait shots. Comments about better AF lock are correct as well…especially if the shot is going to be cropped anyway…but at least for me FX for BIF increases the ‘whole bird in the frame and not clipped’ rate.
Being skeptical by nature, I tested this with my R5 and it does indeed work there too. It can be a simple test. I used a person since they would stay still. I walked back keeping the eye af locked until I got far enough away that it would no longer acquire the eye. Then switching to crop mode I could keep walking back with the eye locked in. I forget the exact numbers, but it was like a 25-30% improvement in subject distance.
stangro
New member
Thanks for all the replies. I'm still confused, however. So, let me rephrase my question.
I'm shooting my Nikon Z9 with my 500mm PF lens. To get the best image quality with subjects that do not fill the FF sensor, is it better to switch to the camera's DX mode, attach my 1.4 TC (in FF mode), or just crop the original FF pic via computer?
Note 1: I am not too concerned with subject AF detection since the Z9 does a fine job of subject detection (especially with its latest firmware update).
Note 2: SCoombs states you get more pixels using a TC. I don't see how this can be since the DX mode and a TC do the exact same thing (cut off the outer portions of the frame).
I'm shooting my Nikon Z9 with my 500mm PF lens. To get the best image quality with subjects that do not fill the FF sensor, is it better to switch to the camera's DX mode, attach my 1.4 TC (in FF mode), or just crop the original FF pic via computer?
Note 1: I am not too concerned with subject AF detection since the Z9 does a fine job of subject detection (especially with its latest firmware update).
Note 2: SCoombs states you get more pixels using a TC. I don't see how this can be since the DX mode and a TC do the exact same thing (cut off the outer portions of the frame).
A tc magnifies, giving you a 700mm full frame lens for all intents. Cropping or crop mode just uses the center pixels and discards the rest. More noise with cropping and the IQ starts to degrade a bit. Still, you can get good results with the crop mode especially if you don't crop the crop mode. It it is how good is the TC and how good is the lens you put it on.
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SCoombs
Well-known member
A TC doesn't cut off the outer portion of the frame: it adds additional lens elements which magnify the the center portion of the image from the lens and project it on the entire sensor. The difference between a lens with a TC attached vs. a lens without one is not exactly the same, but is sort of similar, to the difference between a 200mm lens and a 300mm lens: the 300mm lens has elements in it which magnify the image to a greater degree than the 200mm lens does, just as a TC introduces additional elements in which magnify the image over what the bare lens would do.
For instance, your Z9 sensor is 45.7MP. If you hit DX mode, it cuts off the outer edge so you wind up with an image that only is 19.1 MP. If, on the other hand, you attach a TC, the TC magnifies approximately the same image that would have covered 19.1 MP in DX mode so that that same image covers the full 45.7 MP. Think of it like putting on eyeglasses or using a magnifying glass: you really are making what you see clearer and more detailed by putting the light rays through a real lens.
Generally speaking…you will get better image sharpness with the TC…you have more pixels on subject but slightly less sharpness because of the TC but the pixels on subject wins most of the time. Crop a little more in post if needed. The Z lens accept the TCs better than the F lenses do…so when/if you get Z lens then using the TC has practically no effect on I Q and pixels on subject wins. Short answer…choose the TC first and then crop.
stangro
New member
Understood - thanks!
While using a Nikon 1.4 looses some image resolution I found with the D850 the resolution loss was a little less than the inevitable resolution loss reducing MP by over 50% choosing DX mode.
I find the Nikon S 1.4 converter looses less resolution with a compatible Z lens than the F mount 1.4 converter with a compatible F lens - putting it a little further ahead of cropping to DX mode.
It matters little that a 1.4 converter is equivalent to a 1.42 crop and choosing DX mode is equivalent to a 1.5 crop - other than the result is not identical.
Using DX mode is distinctly less expensive than buying a Z mount TC converter.
I find the Nikon S 1.4 converter looses less resolution with a compatible Z lens than the F mount 1.4 converter with a compatible F lens - putting it a little further ahead of cropping to DX mode.
It matters little that a 1.4 converter is equivalent to a 1.42 crop and choosing DX mode is equivalent to a 1.5 crop - other than the result is not identical.
Using DX mode is distinctly less expensive than buying a Z mount TC converter.
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@Steve covered this nicely with blog posts and videos a while back. From the image quality standpoint this info still holds up in the mirrorless world with perhaps the IQ resulting from TC use being a bit better these days only because the newest mirrorless TCs are a bit better than some of the older TCs. This doesn't get into focus acquisition differences but IQ, DoF impacts, effective ISO impacts are still impacted the way those things were in DSLRs.
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stangro
New member
Thanks DRwyoming
MikeInMI
Active member
One leaves you with a smaller image size in terms of number of pixels. The other slightly impacts IQ, but IMHO and experience, not enough that I can see.
apakett
Member
Both cropping and a TC magnifies the center portion of the lens and all imperfections that it contains. The TC has additional elements to accomplish that along with any degradation that it produces. Cropping causes a loss of pixels. I tested the Z100-400, both with and without a TC. Pixel peeping both showed slightly better results by cropping.
For wildlife shooting ISO noise will likely be your main image quality limitation. Therefore, either a TC or DX mode will produce the same results.
For wildlife shooting ISO noise will likely be your main image quality limitation. Therefore, either a TC or DX mode will produce the same results.
apakett
Member
A TC magnifies the entire image, producing a larger image circle. The sensor cuts off the center portion. Cropping or DX mode does the same thing digitally and causes a loss of pixels. A well designed longer lens, like the example you presented, does not do that.
If your printing images, at what size of print do you see differences in DX vs tc. I’ve printed many prints up to 20x30 with both crops and TCs from lower resolution cameras. Generally I don’t have a need to print anything bigger than that. I have done a landscape print from a d500 that was 42x70in. It would have looked better when looking with say a full frame camera but most observers wouldn’t have noticed.
It does- especially eye detection on distant small birds improves with DX. I have both (on a F mount 600 f4E adopted to Z9) which gets me from 600 to 840 w/TC and to 1344 with TC+DX. hard to argue against...
don't forget you lose one stop of light with a 1.4 tc and 2 stops with a 2.0.
apakett
Member
You also loose one stop of effective ISO with a 1.4x crop or two stops with a 2x crop.