1200mm: Digital Teleconverter

Started 9 months ago | Discussions
Eric Nepean
Eric Nepean Veteran Member • Posts: 5,660
Not Interpolation Re: 1200mm: Digital Teleconverter

Note that the Digital Teleconverter function is only for JPEG files, it is not available for RAW files.

There is a reason for that.

Typical JPEG processing discards well over half the image detail.

Building a really good interpolater is an expensive and tricky job. Hard to do and hard to maintain.

It would be downright crazy to throw out much of the image data, and then develop an expensive and tricky interpolation function to bring it back.

IMO what Panasonic and Olympus have done is selected the center portion of the image, and tweaked the JPEG engine to keep much more of the detail.

JPEG typically averages color values are typically average over at least 4 adjacent pixels, simply not averaging will provide the required detail.

In the Luma channel, much of the detailed information is discarded by normalising  the DFT results with the quantisation matrix and rounding. Changing the quantization matrix is a straightforward way to keep a lot more detail.

This explains why the DTC is not available in RAW.

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Cheers
Eric
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boxerman Senior Member • Posts: 1,808
Downsizing?
1

Henry Richardson wrote:

... I have found that if I then downsize the 20mp photo to 10-12mp on my computer it usually looks pretty darn good. For some images even the full 20mp looks good.

Why does the downsize look better, even sometimes? If there are no artifacts to average out, I don't know why the downsize would look better. (Except that sometimes you can/should sharpen higher res images more. People say that often enough for High Res mode on Olympus.)

I use DTC without fear in "emergencies," i.e., when the lens just doesn't have the reach. It's pretty much this, or lose the shot. Yes, you can crop in post, but it's much easier in-camera with other perks you get (more accurate metering and better view in the viewfinder.) I also suspect since the camera might do a little better than after-the-fact crop, but I can't offhand say why.

Here's a shot I got with my E-M5 (before pro-capture!), 75-300, DTC. Not suitable for large prints (as we often do), but nice enough to capture the moment I'll always remember.

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The BoxerMan

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OP Henry Richardson Forum Pro • Posts: 19,135
downsizing
3

stevevp wrote:

Probably daft question. How do you downsize the 20mp photo to 10-12mp?

The way I do it is I import all my photos into Lightroom and then if I want a 10mp or 12mp or thereabouts file I export it to that size.  Also, can do it in Photoshop, Paint Shop Pro, Gimp, Irfanview, or any other software.

If you want to do it in camera though then you can set the jpeg size to 10mp on the PEN-F, etc.

Note, that you don't have to downsize.  I have the 20mp (or 16mp) jpegs imported into Lightroom.  I am just saying that the camera (in the case of a 20mp sensor) takes the central 5mp and interpolates it up to 20mp.  Interpolating it up to 10-12mp is a smaller lift and looks better, naturally.  For prints it probably doesn't matter anyway though because the printer driver will do its own interpolation.  I haven't printed any of the DTC shots, but for onscreen viewing 10-12mp instead of 20mp is noticeable.

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Henry Richardson
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JimH123 Senior Member • Posts: 2,805
Re: Is The Digital Tele-Converter Feature In Your OMD Camera Worth Your While?
1

stevevp wrote:

Probably daft question. How do you downsize the 20mp photo to 10-12mp?

Thanks.

Please understand that downsizing is a technique that can be used to reduce noise in an image.  The act of compressing is likely to cause some certain amount of noise to be averaged out so that it is not noticeable.  The downside is that you have reduced the resolution of the image.

If your image does not have much noise, there is likely no need to downsize.

Or, a product such as Topaz's Denoise AI is superb at removing noise while preserving detail.

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OP Henry Richardson Forum Pro • Posts: 19,135
Re: Downsizing?

boxerman wrote:

Henry Richardson wrote:

... I have found that if I then downsize the 20mp photo to 10-12mp on my computer it usually looks pretty darn good. For some images even the full 20mp looks good.

Why does the downsize look better, even sometimes? If there are no artifacts to average out, I don't know why the downsize would look better.

DTC interpolates 5mp to 20mp. In other words, 1 pixel becomes 4 pixels. If you downsize to 10mp then 1 pixel becomes 2 pixels. In your photo editing software on your computer I suggest you uprez a photo:

  1. 2 times the pixels
  2. 4 times the pixels
  3. 8 times the pixels

Take a look at each of them at 100%.  Also, see this:

https://www.dpreview.com/forums/post/64241372

I use DTC without fear in "emergencies," i.e., when the lens just doesn't have the reach. It's pretty much this, or lose the shot. Yes, you can crop in post, but it's much easier in-camera with other perks you get (more accurate metering and better view in the viewfinder.) I also suspect since the camera might do a little better than after-the-fact crop, but I can't offhand say why.

Yeah, and it is fun too. Especially for out of this world focal lengths like 1200mm-efl!

Here's a shot I got with my E-M5 (before pro-capture!), 75-300, DTC. Not suitable for large prints (as we often do), but nice enough to capture the moment I'll always remember.

Nice.

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Henry Richardson
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Ken Croft Senior Member • Posts: 1,741
Re: 1200mm: Digital Teleconverter

Henry Richardson wrote:

Those look pretty good. Yeah, I think 4x which uses 1/8 of the pixels and then interpolates is too much. 2x uses 1/4 the pixels and that is as far as you can go, I think. Although for subjects that have very little detail, I suppose, the 4x could work sometimes.

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Henry Richardson
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Actually if 2x uses 1/4 of the pixels then 4x uses 1/16 of the pixels.
Ken C

OldGuy-Yuri Regular Member • Posts: 241
Re: Downsizing?
4

Thank You Henry and all who have contributed to this thread!
I'll admit to having completely ignored the DTC function - ignorance and assumption are terrible things. And we all have hidden pockets of both.
DTC seems to have landed in my hidden pockets. 
But it does look as if DTC can have some fun and interesting results.
so... a thread which shows the true worth of forums like this.
Thanks!
Yuri

stevevp Regular Member • Posts: 423
Re: downsizing

Henry Richardson wrote:

stevevp wrote:

Probably daft question. How do you downsize the 20mp photo to 10-12mp?

The way I do it is I import all my photos into Lightroom and then if I want a 10mp or 12mp or thereabouts file I export it to that size. Also, can do it in Photoshop, Paint Shop Pro, Gimp, Irfanview, or any other software.

If you want to do it in camera though then you can set the jpeg size to 10mp on the PEN-F, etc.

Note, that you don't have to downsize. I have the 20mp (or 16mp) jpegs imported into Lightroom. I am just saying that the camera (in the case of a 20mp sensor) takes the central 5mp and interpolates it up to 20mp. Interpolating it up to 10-12mp is a smaller lift and looks better, naturally. For prints it probably doesn't matter anyway though because the printer driver will do its own interpolation. I haven't printed any of the DTC shots, but for onscreen viewing 10-12mp instead of 20mp is noticeable.

Many thanks to you and JimH123 for your replies. I'll give it a try with Lightroom.

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boxerman Senior Member • Posts: 1,808
Re: Downsizing?

Thanks for responding and also cultivating this thread.

But, I'm still puzzled, if you're inordinately patient:

Henry Richardson wrote:

boxerman wrote:

Why does the downsize look better, even sometimes? If there are no artifacts to average out, I don't know why the downsize would look better.

DTC interpolates 5mp to 20mp. In other words, 1 pixel becomes 4 pixels. If you downsize to 10mp then 1 pixel becomes 2 pixels. In your photo editing software on your computer I suggest you uprez a photo:

  1. 2 times the pixels
  2. 4 times the pixels
  3. 8 times the pixels

Take a look at each of them at 100%.

I don't need to do this experiment as the outcome is obvious. At 100% you see each pixel, so of course you'll see smearing from spreading out one pixel to N. Artifacts also get bigger, so more noticeable.

The fairer experiment is to view uprezes all at the same largish size, near your intended output medium (possibly corrected for the viewing distance--people want very large prints to resolve what they'd see from a foot away; silly. Who inspects a 1-2 meter print from that close?).

In short, viewing at 100% is unfair to higher-resolution images, which get MORE enlargement by the process than lower resolution. In the end, I will display or print at the same size as I want for each image.

I think people make the same mistake about noise. Panic with individual pixel noise. But, if you have a high-resolution image, your eye will effectively average noise across AREAS, not pixels.

But, even if this were a demonstration, I'm still after the "why."  In my comment above, I understand small pixel clusters being effectively averaged by your eye, with it's limited resolution. I understand that PIXEL noise will get reduced by averaging in down-rezing, but again, that might not be perceived noise, at some standard output size and distance.

Also, see this:

https://www.dpreview.com/forums/post/64241372

I did, thanks.

I use DTC without fear in "emergencies," i.e., when the lens just doesn't have the reach. It's pretty much this, or lose the shot. Yes, you can crop in post, but it's much easier in-camera with other perks you get (more accurate metering and better view in the viewfinder.) I also suspect since the camera might do a little better than after-the-fact crop, but I can't offhand say why.

Yeah, and it is fun too. Especially for out of this world focal lengths like 1200mm-efl!

Oh, I forgot to mention before: I put DTC on a button. I put it on my video (orange) button, since I rarely use video and, when I do, can trouble to twirl the knob. That way, it's basically instant to use.

Here's a shot I got with my E-M5 (before pro-capture!), 75-300, DTC. Not suitable for large prints (as we often do), but nice enough to capture the moment I'll always remember.

Nice.

Thanks!

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The BoxerMan

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Eric Nepean
Eric Nepean Veteran Member • Posts: 5,660
Re: Downsizing?
2

boxerman wrote:

Henry Richardson wrote:

... I have found that if I then downsize the 20mp photo to 10-12mp on my computer it usually looks pretty darn good. For some images even the full 20mp looks good.

Why does the downsize look better, even sometimes? If there are no artifacts to average out, I don't know why the downsize would look better. (Except that sometimes you can/should sharpen higher res images more. People say that often enough for High Res mode on Olympus.)

I use DTC without fear in "emergencies," i.e., when the lens just doesn't have the reach. It's pretty much this, or lose the shot. Yes, you can crop in post, but it's much easier in-camera with other perks you get (more accurate metering and better view in the viewfinder.) I also suspect since the camera might do a little better than after-the-fact crop, but I can't offhand say why.

In JPEG  conversion, quite a lot of image fine detail is discarded. If you try to crop after JPEG conversion, the discarded information limits the acheivable resolution.

Noise reduction and sharpening also remove detail.

The camera can do its cropping anywhere the designer wants, and the most logical place for the designer to place a 2X or 4X crop is at the beginning of the image "pipeline" before any detail is discarded or obscured. The JPEG process also offers obvious tweaks or controls to discard less detail.

Many people speeculate that DTC involves interpolation after JPEG conversion and cropping (which is what the photographer is faced with). No system designer in their right mind would build something like this, its far more effective to crop first and not throw out as much image detail.

Here's a shot I got with my E-M5 (before pro-capture!), 75-300, DTC. Not suitable for large prints (as we often do), but nice enough to capture the moment I'll always remember.

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Cheers
Eric
(Any image that I post in a DPR forum may be editted and posted in a DPR forum)

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OP Henry Richardson Forum Pro • Posts: 19,135
Re: 1200mm: Digital Teleconverter

Ken Croft wrote:

Henry Richardson wrote:

Those look pretty good. Yeah, I think 4x which uses 1/8 of the pixels and then interpolates is too much. 2x uses 1/4 the pixels and that is as far as you can go, I think. Although for subjects that have very little detail, I suppose, the 4x could work sometimes.

Actually if 2x uses 1/4 of the pixels then 4x uses 1/16 of the pixels.

Yes, you are correct.  Thanks.

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Henry Richardson
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OP Henry Richardson Forum Pro • Posts: 19,135
Re: Is The Digital Tele-Converter Feature In Your OMD Camera Worth Your While?
1

JimH123 wrote:

Please understand that downsizing is a technique that can be used to reduce noise in an image. The act of compressing is likely to cause some certain amount of noise to be averaged out so that it is not noticeable.

Thanks for that additional info. The reduced perceived noise by downsizing has been my understanding also going back for many years.

The downside is that you have reduced the resolution of the image.

In the case of DTC images a 20mp image doesn't really have 20mp of resolution anyway so reducing it to 10mp is not really throwing any resolution away. It is just making it look less like it has been upsized from 5mp to 20mp.   5mp to 10mp is a much smaller lift so the results can usually look quite good.

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Henry Richardson
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OP Henry Richardson Forum Pro • Posts: 19,135
Used Canon 1200mm for $180,000
4

You could instead buy a used Canon 1200mm f5.6 for $180,000 and a Canon DSLR since that is also an option:

https://petapixel.com/2015/04/28/bh-is-selling-a-used-canon-1200mm-f5-6l-lens-for-just-180000/

Up Close with the Canon EF 1200mm f/5.6 L USM Lens

https://www.bhphotovideo.com/c/find/newsLetter/Canon-EF-1200mm.jsp

https://en.wikipedia.org/wiki/Canon_EF_1200mm_lens

With extreme care and perfect conditions you will be able to get great results with that lens. Or for about $400 (that is how much I paid for my new Olympus 75-300mm II) and DTC you can often get pretty close since atmosphere, heat waves, haze, etc. often degrades long distance photos anyway. For closer photos then the Canon has the edge. But not too close because the Canon's minimum focus distance is 49.5 feet (15 meters)!!!  The Olympus focuses to less than 3 feet (90 centimeters).

By the way, even when I occasionally shoot at pseudo 1200mm-efl I do it handheld in a small, light kit. Try that with the Canon 1200mm + 1D level DSLR.

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Henry Richardson
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OutsideTheMatrix
OutsideTheMatrix Veteran Member • Posts: 7,851
Re: 1200mm: Digital Teleconverter

I love these!  I see more detail in my moon shots with this than I do without using DTC.

Sometimes I also shoot at M size 5 MP and then get a non interpolated camera cropped result which is also good for birding since it gives me a faster rate of burst shooting (especially with the fully electronic shutter)

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In the councils of government, we must guard against the acquisition of unwarranted influence, whether sought or unsought, by the military industrial complex. The potential for the disastrous rise of misplaced power exists and will persist. We must never let the weight of this combination endanger our liberties or democratic processes. We should take nothing for granted. Only an alert and knowledgeable citizenry can compel the proper meshing of the huge industrial and military machinery of defense with our peaceful methods and goals, so that security and liberty may prosper together.
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OP Henry Richardson Forum Pro • Posts: 19,135
IQ vs. QI
7

OldGuy-Yuri wrote:

Thank You Henry and all who have contributed to this thread!
I'll admit to having completely ignored the DTC function - ignorance and assumption are terrible things. And we all have hidden pockets of both.
DTC seems to have landed in my hidden pockets.
But it does look as if DTC can have some fun and interesting results.
so... a thread which shows the true worth of forums like this.
Thanks!
Yuri

Thank you, Yuri. IMO, the obsession on these forums with anal retentive efforts to get the highest technical quality (often for no real purpose) while in so many cases not caring about actually getting interesting photos goes too far. In other words, too much emphasis on IQ (image quality) and not nearly enough on QI (quality image). And I don't mean that IQ is never important, far from it, and in some situations it is very important. It just seems to me that a lot of people have no balance. But that is just my opinion.

I posted this on 2007-9-14:

IQ = Image Quality (strictly on the technical aspects of the sensor, etc. -- noise, noise reduction artifacts, sharpness, and so on) and it should not be confused with the much more important QI = Quality Image. To have high QI you need to be a good photographer.

https://www.dpreview.com/forums/post/24828803

Worry more about QI (quality image) than IQ (image quality) and your photography will be much better. And this applies to lenses too.

I wrote this several years ago:

Ramblings about Travel and Photography

http://www.bakubo.com/ramblings.html

Here is one bit:

In my opinion, a whole lot of people get way too obsessed about technical image quality (extreme sharpness, minimal distortion, minimal chromatic aberration, etc.) and almost totally ignore making quality images. Personally, I also chuckle when I hear someone repeat the old saw about it being "all about the glass" or "all about the lenses." Spend time looking at photos over the past 50-100 years. Notice how many of those that are so wonderful are wonderful almost always because of subject, composition, timing, lighting, etc. and almost never because of the particular lens and whether it was marginally sharper, had slightly less distortion, and so on than another lens. Let the gearheads who do not actually take many photos worry themselves to death about that stuff. Take photos and you will get better. Obsess over gear and you will just end up being a gear fanatic. You just can't buy your way to good photos, but getting out there with the gear you have and taking photos, looking at other people's photos, and thinking will improve your vision and skills so that you can start taking good photos.

I do understand the attraction of quality gear, the aesthetics, the tactile feel, the perceived status conferred, and so on though. I just also understand that a lot of people get sidetracked in their hope to take photos they really like by getting on the gear track. Also, there are people who love cameras and gear as a hobby and are not all that interested in photography. Nothing wrong with that. It's your money and you can do with it what you want -- after you have paid all of your taxes to various government entities that demand the first cut, that is. All just my opinion, of course.

"I'm always amused by the idea that certain people have about technique, which translate into an immoderate taste for the sharpness of the image. It is a passion for detail, for perfection, or do they hope to get closer to reality with this trompe I’oeil? They are, by the way, as far away from the real issues as other generations of photographers were when they obscured their subject in soft-focus effects." -- Henri Cartier-Bresson

And also, let's have some fun with our cameras. Almost everyone could use a bit of fun, particularly in 2020. I, for one, think that having a pseudo 1200mm-efl is totally wild. Years ago I would never have even dreamed of that. Sure, 1200mm-efl is not the most useful focal length, but it certainly gives a view that most of us are not accustomed to. And I can usually even handhold it! Crazy, man! With the 100-400mm lenses you could even get a pseudo 1600mm-efl. Who wudda thunk not so long ago?

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Henry Richardson
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OutsideTheMatrix
OutsideTheMatrix Veteran Member • Posts: 7,851
Re: That Google DTC is pretty cool

JakeJY wrote:

Henry Richardson wrote:

JakeJY wrote:

A real TC will almost always result in a better image, but the problem with a real TC is you have to first have one and you also have to attach it. Digital teleconverter (or Digital Zoom in Panasonic cameras) comes free with the camera and is a button away.

Kind of off topic, but I wish camera manufacturers can try some of the super resolution modes like Google Pixel does. It's similar to but not quite as demanding as HHHR. By using this only tied to digital zoom, it allows the camera to ignore the unused parts of the sensor area and get a faster burst of images.

https://ai.googleblog.com/2018/10/see-better-and-further-with-super-res.html

I had not heard of that. Pretty cool. Do you think the processors in our cameras can handle it? They can do handheld HDR where they merge several photos while aligning them and many other things. This looks like another area that the camera companies should learn from what is being done in smartphones.

For a 2x zoom, it would only be processing 1/4 of the data that something like HHHR does, so it should help a ton on reducing the processing demands. Might make the feature viable in a lot more cameras. The other thing camera makers need to do is much better AI to reduce motion artifacts. That's something current in-camera HDR mode and HHHR generally does a poor job of doing.

Absent of this, having a continuously variable digital zoom would be useful. My Panasonic only comes with 2x or 4x. 4x is a bit too much, 2x works ok, but it would be much nicer to be able to get other values (even less than 2x). For example, if I want something between 140-280mm (on my 14-140mm), the current digital zoom implementation means I'm unnecessarily throwing away 3/4 of my sensor area to achieve that.

I think Olympus just has 2x, but maybe I have missed something. I have the Panasonic GX7II (GX85) and I have not explored this function yet.

I have GX85 and it has 2x and 4x. It's under MENU > [Rec] > [Digital Zoom]. For quick access, this can be assigned to a function button.

Ummm I have just started doing this (did you read my OP on the topic and my post earlier in this thread about it?) Basically I programmed M size 5 MP into my camera into the 2nd and 3rd slots (1st and 4th slots are both L size.) So what happens when I activate x2 DTC through one of the Fn buttons, I can also use another Fn button to switch from L size to M size and then get a non interpolated result using x2 DTC (well close enough, since it is 5 mp instead of 4 mp). This results in faster burst shooting especially with the fully electronic shutter on my EM10Mk2.

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In the councils of government, we must guard against the acquisition of unwarranted influence, whether sought or unsought, by the military industrial complex. The potential for the disastrous rise of misplaced power exists and will persist. We must never let the weight of this combination endanger our liberties or democratic processes. We should take nothing for granted. Only an alert and knowledgeable citizenry can compel the proper meshing of the huge industrial and military machinery of defense with our peaceful methods and goals, so that security and liberty may prosper together.
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OutsideTheMatrix
OutsideTheMatrix Veteran Member • Posts: 7,851
Re: 3000mm or 4000mm

Henry Richardson wrote:

Max Iso wrote:

It's definitely an interesting feature but i think more so for video. I don't know what the exact crop increase is but since video "rez" output doesn't change from full sensor to ETC, it turns into a pretty neat feature.

Turning on ETC and digital IS on a 4k body is pretty amazing, in the near future im going to try it out on my 1250mm C90 scope. Not sure what the final FL will be but im guessing 3000mm+, maybe even 4000mm.

I think Nikon has a small sensor camera with a very, very long zoom. 3000mm or so. With your scope you could play around and get some interesting photos, I think. Use your imagination. Probably not great for boring bird photos, but be creative is my suggestion.

I have the Nikon P900 and I believe the camera you are referring to is the Nikon P1000.  The Nikon P950 is the camera that supports 4K30 video.  What I dont know and want to find out is if any camera supports in camera cropping of 2K (for 1080P) videos or in camera cropping of 4K videos.  I dont think any M43 cameras do or any camera of the Nikon P series for that matter?

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In the councils of government, we must guard against the acquisition of unwarranted influence, whether sought or unsought, by the military industrial complex. The potential for the disastrous rise of misplaced power exists and will persist. We must never let the weight of this combination endanger our liberties or democratic processes. We should take nothing for granted. Only an alert and knowledgeable citizenry can compel the proper meshing of the huge industrial and military machinery of defense with our peaceful methods and goals, so that security and liberty may prosper together.
-Dwight D. Eisenhower, 1961

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OutsideTheMatrix
OutsideTheMatrix Veteran Member • Posts: 7,851
Re: Not Interpolation Re: 1200mm: Digital Teleconverter

Eric Nepean wrote:

Note that the Digital Teleconverter function is only for JPEG files, it is not available for RAW files.

There is a reason for that.

Typical JPEG processing discards well over half the image detail.

Building a really good interpolater is an expensive and tricky job. Hard to do and hard to maintain.

It would be downright crazy to throw out much of the image data, and then develop an expensive and tricky interpolation function to bring it back.

IMO what Panasonic and Olympus have done is selected the center portion of the image, and tweaked the JPEG engine to keep much more of the detail.

JPEG typically averages color values are typically average over at least 4 adjacent pixels, simply not averaging will provide the required detail.

In the Luma channel, much of the detailed information is discarded by normalising the DFT results with the quantisation matrix and rounding. Changing the quantization matrix is a straightforward way to keep a lot more detail.

This explains why the DTC is not available in RAW.

But it is only throwing away data that is outside the area of interest and which may not be of any interest to the photographer. I shoot RAW+JPG now (only the JPG file part shows the DTC), why doesn't Oly make the x2 DTC filter available in Work Space so people can apply it to their RAWs? It should work the same way! Also, I sometimes use M size 5 MP for x2 DTC to get a nearly non interpolated result (5 MP vs 4 MP not much different) to get a much faster burst shooting rate, especially with the fully electronic shutter on my EM10Mk2.

But when using x2 DTC at the full 16 MP I do see more crater detail on the moon than I see without the DTC.

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In the councils of government, we must guard against the acquisition of unwarranted influence, whether sought or unsought, by the military industrial complex. The potential for the disastrous rise of misplaced power exists and will persist. We must never let the weight of this combination endanger our liberties or democratic processes. We should take nothing for granted. Only an alert and knowledgeable citizenry can compel the proper meshing of the huge industrial and military machinery of defense with our peaceful methods and goals, so that security and liberty may prosper together.
-Dwight D. Eisenhower, 1961

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OutsideTheMatrix
OutsideTheMatrix Veteran Member • Posts: 7,851
Re: Downsizing?

You're not wrong....I recently made a thread about this..... JPG processed from RAW are half the file size (even in super fine mode) vs JPG straight out of the camera.

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In the councils of government, we must guard against the acquisition of unwarranted influence, whether sought or unsought, by the military industrial complex. The potential for the disastrous rise of misplaced power exists and will persist. We must never let the weight of this combination endanger our liberties or democratic processes. We should take nothing for granted. Only an alert and knowledgeable citizenry can compel the proper meshing of the huge industrial and military machinery of defense with our peaceful methods and goals, so that security and liberty may prosper together.
-Dwight D. Eisenhower, 1961

 OutsideTheMatrix's gear list:OutsideTheMatrix's gear list
Nikon Coolpix P900 Olympus PEN E-PL6 Olympus OM-D E-M10 II Olympus M.Zuiko Digital 14-42mm 1:3.5-5.6 II R Olympus M.Zuiko ED 75-300mm 1:4.8-6.7 II +9 more
OP Henry Richardson Forum Pro • Posts: 19,135
Pseudo 1200mm-efl with 75-300mm f4.8-6.7 II
5

All the photos I have posted in this thread were taken at 300mm f6.7 (wide open) and that is supposed to be the worst focal length and the worst aperture at 300mm.  Personally, I find that as long as I take care about camera shake (IBIS helps a lot, but at such a long focal length you need to take great care to keep the camera steady), atmospheric haze, etc. that it is still quite sharp.  Using the DTC you are getting the central 25% of the image, which is the sharpest part, to interpolate from.

I should note that in all my shots I sort of screwed up because I had left my camera set to JPEG Normal rather than Fine or Super Fine.  The results would have been slightly better using Super Fine or Fine instead of Normal.  Having said that, even at Normal I was satisfied, particularly if the 20mp (or 16mp) file was downsized some.

I haven't used the DTC since 2017 when my 75-300mm was new.  I was having a ball with it for awhile taking very long telephoto shots at 300mm with DTC (pseudo 1200mm-efl) and without DTC (600mm-efl).  Now I feel like taking it out for a spin again.

On these forums one often gets the impression that long telephotos are just for birds or the moon.  And one often gets the impression on these forums that wide angles are just for landscapes.  I suggest that you use your imagination.

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Henry Richardson
http://www.bakubo.com

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