Author Topic: RAW, JPG or TIFF  (Read 1958 times)


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« on: March 09, 2020, 06:56:31 PM »
Hi and thanks to welcome me in the community (I'm a new Metashape user).
I've got plenty of questions but won't bother you with all at the same time ;)
My most urgent one concerns the format of the images.
I capture the images with a DJI Mavic 2 Pro drone (1 inch Hasselblade) and can use jpg or dng (raw).
The jpg are good quality (more than 10 Mo 5472x3648).

1- Do you think it can be a real improvement if I use RAW in Metashape ?

If yes, I've read in the manual that the best is to convert to uncompressed TIFF.

2- As Metashape can read and work with my DNG, why is it important to convert and why shouldn't I use DNG ?

3- In the change log of the 1.6.2, I read : "• Updated DNG loader to apply BaselineExposure scaling.". I really don't understand what that means.... Couldn't it be that "Yes ! Now you can use DNG directly and get the best results!" ?

Thanks to all for your help.

Cyril from France


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« Reply #1 on: May 16, 2020, 03:37:58 AM »
I want to share some relevant info to heat this topic up. The zinger - I seem to get better (aerial mapping) results with JPEG than DNG. For all you fancy HDR EXR 32-bit float color wizards out there this probably isn't relevant, but thanks for your posts, and especially the xkcd link. It gave me a sanity check.

TLDR - With optimal post-processing, I can get ~5-10% "better" results (so far) with JPG/TIFF compared to DNG. --Alexey or someone at Agisoft - Why?!-- Colorblind-friendly screenshot attached showing a tantalizingly blurry draft table of results from tests with one of two datasets. cool blues are "better", warm reds are "worse" and white is 50th percentile.

I define "Better" as higher initial tie-point count and count after gradual selection optimization, while not worse error/RMSE. Camera position error is generally within 1-2 mm (xyz), RMS reprojection error is within ~0.002 pix, and mean keypoint size is slightly smaller. Exactly what makes things better is elusive, but the raw conversion software is a primary factor. So far I get the best results with Affinity Photo (beta) raw converter. Capture One (Express for Sony) comes in second, followed by DNG which doesn't give me any options and is my "baseline" raw. JPG seems barely worse than TIFF with a significant size advantage, but possibly slower processing (next phase of testing if I bother).

--longer version below with more detail--
I am intrigued by initial results comparing dng vs tiff vs jpg. Mostly I've focused on dng vs JPG since at ~95-100% quality (no chroma subsampling, floating-point discrete cosine transform) there is not a lot of visual difference between the two, while JPGs are ~25%-75% smaller within that range. This will be more relevant to aerial mapping than HDR 3D modeling since our focus is on 3D mapping with orthos as a complementary but usually not primary product.  Our focus is on optimizing processing speed, accuracy, and project size.

I just spent an æon [time is blurry in this strange pandemic world] generating and processing JPGs, TIFs and DNGs with a variety of settings and colorspaces in more than a hundred iterations with two sets of .ARW files from a Sony A7R; one with 120 images and one with 1000 images. I'm wrapping up a few things on the 1000 image set, but it seems to generally prove out the best results from the 120 image set. All of my post-processing tried to work primarily with raw processors, colorspaces, levels, exposure, tones, and base curves. I didn't do any denoising, sharpening, lens correction, chromatic aberration correction, etc. One of the most frustrating aspects was the way that different raw converters honor (or don't) the sensor crop values, which I don't even understand.

From what I HAVE been able to understand about metashape processing (thanks for your posts Alexey), Metashape uses the raw image values for each pixel. I don't know if there's any "auto-leveling" step in the image-matching algorithms, but I don't think so, since adding auto-leveling seems to improve results for a given dataset, provided that the auto-scaling doesn't make images too different. I would dearly love some insight into what the image-matching algorithms are most sensitive to. I am curious about the DNG baseline exposure scaling, and I wonder if some kind of "auto-leveling" preprocessing step algorithm would make a difference - I'm guessing that an image-by-image auto-leveling wouldn't be quite as good as a running average for adjacent images (maybe a refinement step?). In general in my peeks at image characteristics it seemed like processing workflows that generated fewer unique colors might produce slightly better results but a lot of those details are fuzzy to me (I'm a geologist, Jim, not a colorspace wizard!).

The imagery has PPK GNSS trigger-event-based camera positions with lever arms to GNSS antenna. I am processing with only camera positions, and evaluating error between photosets after processing.


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« Reply #2 on: May 17, 2020, 10:49:10 AM »
With RAW files it really does depend on the converter used. Compare a Jpeg/Tiff saved out from ACR with some other converter. There are often large quality differences.


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« Reply #3 on: May 17, 2020, 06:27:44 PM »
That is sort of what the point of my post was, with the exception that I didn't try Adobe. See below.

My real surprise wasn't with the JPEGs relative to each other, it was with the JPEGs relative to the DNG, which is the closest thing to raw that Metashape can process. I thought that since Metashape supports DNG, which is effectively the camera raw (I know a lot of professional photographers disagree with this) and has the highest bit depth, DNG would give me the best results. Based on processing recommendations from Metashape, I expected JPEG to be a compromise, not an improvement.

Adobe Camera Raw is the only software that required a credit card number to sign up for a subscription in order to even test, and their customer service attitude doesn't impress me. I used their software extensively until they started the subscription model, but I don't really have much interest in using it now. I'm a little curious if it would produce better results than Affinity and Capture One, but I haven't jumped through their hoops with a personal credit card since this is for work, and my employer requires Adobe to be purchased through a contract and a vendor. I thought about trying their software with the old pre-subscription version that I have, but that wouldn't really be fair to them.

I will update my results with Adobe products if I figure out a way to try the current version. I already spent 2 hours in a chat with people that kept repeating the same thing to me and asking for my credit card number, so I'm not particularly motivated to do anything else with them at this point.