Re: XT5 using Digital Teleconverter and further crop to get Canon 1D - like files
fjablo wrote: AleDiSciascio wrote: fjablo wrote:
Had the same impression of someone not really looking for feedback..
For what it’s worth:
Cropping a 75mm lens to 200mm (300mm FF equivalent) on the X-T5 leaves you with a file that’s 2.905x1.937. Any upscaling is hit and miss so I wouldn’t count on that.
If set to f/1.4 the DOF would be equivalent to f3.7 (f5.6 FF equivalent)
Imo a much better option would be getting a MFT camera with the 40-150mm f2.8, or even the 35-100mm f2.8 and cropping in.
But if you only want to crop in in a pinch and usually stay closer to the original 75mm, then I guess yes you can do smaller prints with those 5.6mp files
I guess the reality is that:
A. I DID want feedback on things like "your math is wrong" or "I've tried something like this and cropped in the Viltrox 75 1.2 is SHIT" or for instance "keep in mind that while the viltrox is awesome shot normally even at 1.2 ... if you were to use that lens with the Digital Converter and then applied an additional crop to the resulting file, the DOF performance of that gorgeous 1.2 lens at say a distance of 20 meters from the subject would be complete ASS..." <--- that is feedback I got and when I went looking with a DOF calculator unless I'm doing the math wrong it's even FAR WORSE than I was told... if I'm calculating correctly... shot at F1.4 the 75mm viltrox then cropped in to be a 337 equivalent would have the same DOF as a full frame lens shot from the same position at something insane like F19. I also welcomed feedback about using upsampling software and being careful about high iso
B. I DID NOT want feedback on things like "not enough pixels for a good print" since I've run into pixel-peepers who obsess over 300+ppi for prints for almost two decades and while I respect their right to their opinion I disagree with their conclusions IN MOST normal circumstances.
Either way... the feedback I've received has in fact changed my mind from "this could be a useful trick to use whenever I want" to "this might end up being just an emergency solution and definitely not something I want to use with any frequency" ... so regardless of how I came across, the feedback was useful and it impacted me.
Pretty sure that DOF calculation is incorrect. A 75mm lens at f/1.4 has an aperture opening of 53.6mm, exactly the same as a 300mm lens at f/5.6. For your 337mm example it's more like f/6.3. Shot from the same position, they should give the same DOF.
I suspect the DOF calculators fall short here because they're always based on viewing the full image, not at pixel-level. So they put out a higher DOF number for the 75mm image on the Fuji because that's what might look "acceptably sharp" at a normal viewing distance. Cropping in essentially magnifies part of the image and reveals that a smaller area is "acceptably sharp".
Ultimately, the appearance of background blur and subject isolation (to avoid the term DOF as it's a fuzzy concept with lots of assumptions) only depend on the aperture size (so focal lengths / aperture value) and subject distance. Sensor size or cropping are only relevant for the FOV.
Nothing to do with pixels, it's a matter of magnification, the DoF calculation includes consideration of magnification to produce the print, if you crop, magnification increases and less DoF is evident. Doesn't matter how many pixels you have. Unless you crop so much you can see the pixels, as with grain in film.
Gerry
Jul 10, 2025 at 03:41 PM
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