Helios: photo and RAW editor in your browser

Helios is a photo editor that you open in your browser like any other web page. There’s nothing to install, no account to create and nothing to pay when you save. Your original file stays untouched, because saving always creates a new file.

In Helios you can brighten a photo that came out too dark and tone down a sky that’s too bright, remove a yellow or blue tint, crop the photo and level a crooked horizon, and sharpen it and reduce noise. There are 100 ready-made filters, and you can save your own. You can copy the settings from one photo to a whole set, for example all the photos from a wedding, and then save them all at once, sized for email, a website or social media.

The editor opens with the Open Helios button at the top of this page and fills the whole screen. The Arteon icon in the top left corner of the editor closes it and brings you back to this page. If you opened the editor with that button, your browser’s Back button does the same. Ads only appear in a separate column along the right edge of the editor, or in a narrow strip at the very bottom on phones and other small screens, so they never cover the photo or the buttons.

A RAW file holds the unprocessed data from the camera’s sensor rather than a finished picture like a JPG or TIFF. Cameras usually record this data with 12 or 14 bits per channel, while a JPG has 8, so a RAW file holds a much wider range of brightness[1]. Turning the raw data into a photo is called developing[1]. You can develop the same file as many times as you like, with a different white balance each time, for example. A JPG can’t be turned back into RAW, because some of the data was thrown away when it was compressed.

Every manufacturer has its own format: Canon saves CR2 and CR3 files, Nikon NEF, Sony ARW, Fujifilm RAF, Panasonic RW2 and Olympus ORF[1]. So a NEF or CR3 file is simply a RAW file with its maker’s extension. DNG is an open RAW format created by Adobe[2], and phones such as the Google Pixel and Samsung Galaxy save their RAW photos as DNG. Most RAW files also contain a ready-made JPG preview, which the camera shows on its screen[1]. Helios uses it too: the photo appears after about 0.2–0.3 s, and editing starts once the editor has developed the whole file.

HEIC is the format that iPhone 7 and later, iPad (6th generation) and later and newer iPad Air, mini and Pro models use for photos when they run iOS 11 or later. It replaces JPG on these devices because it compresses better, so a photo takes up less space[3], but like a JPG it holds a finished picture rather than raw sensor data. If you’d rather your iPhone saved photos as JPG, open the Settings app, tap Camera, then Formats, and choose Most Compatible[3].

After clicking Open photos, select several photos in the file picker, or drag a whole set onto the editor. The empty editor says Drop photos here, and while you drag it shows Drop to add photos. You can add more files later with the plus tile (Add photos) at the end of the thumbnail strip at the bottom of the editor.

All the photos you choose appear in the thumbnail strip straight away, in the order you picked them, including those still opening, and the progress shows next to the strip, for example Opening photos: 3 of 10. The editor opens up to three photos at a time, depending on your processor cores and memory. Clicking a photo that’s still waiting opens it next, and closing a waiting photo stops it from opening. Thumbnails of RAW files come from the previews saved by the camera, so the strip fills up within a few seconds, before the whole set has opened. In our test, the editor opened a set of 200 photos of 800 × 600 px in 35 s, and the page responded to clicks the whole time.

An animated GIF, WebP or PNG and a multi-page TIFF open on their first frame or page. A row such as Frame 1 of 12 or Page 1 of 5 then appears under the histogram, with a Choose a frame or Choose a page button that shows all frames as thumbnails. You edit and save one frame or page at a time, as a regular photo without animation, and the frame or page number goes into the file name, for example scan-page-2-helios.png.

The Light section on the right is open as soon as the photo loads. The easiest place to start is the Auto button: the editor sets the light for this photo, and you can then adjust any slider. The button brightens a dark photo, but it won’t darken a bright one that isn’t overexposed. It also makes sure the bright areas don’t blow out.

• Exposure brightens or darkens the whole photo at once, from −5 to +5. It’s the first slider to reach for when a photo is simply too dark or too bright.
• Contrast increases or reduces the difference between the light and dark parts of the photo.
• The Highlights slider only affects the bright parts. Moved to the left, it darkens a bright sky or window without darkening the rest of the photo.
• The Shadows slider only affects the dark parts. Moved to the right, it brightens a face or a building in a photo taken against the light.
• Whites and Blacks set the brightest and darkest points of the photo. They help when a photo looks grey and flat after your other changes.

The other sliders in this section run from −100 to +100, and they all start at zero. Next to each slider there’s a number field where you can type an exact value. Double-clicking a slider sets it back to zero, the Reset button resets the whole section, and Restore original undoes every change to the photo.

Helios opens RAW files at 16 bits per channel. The brightest parts of the photo, which a normal development would turn pure white, then stay in the data as extra headroom, and the Exposure, Highlights and Whites sliders can use it without clipping. That’s why moving the Highlights slider to the left brings back detail in the brightest areas, which at 8 bits per channel would stay a flat grey patch. This applies to areas that only went past white during development. If the camera sensor itself clipped the light, there’s no detail in the file, so the editor can’t bring it back, but it does remove the purple tinge from those areas. A very large photo on a device with little memory opens at 8 bits per channel, and the editor tells you so once. Helios edits JPG, PNG, TIFF and other formats at 8 bits per channel.

A yellow, orange or blue tint over the whole photo, which photographers call a colour cast, comes from the colour of the light the photo was taken in. A photo taken indoors under ordinary light bulbs comes out yellowish orange, and one taken in the shade on a sunny day comes out blue[5]. White balance corrects for the colour of the light so that neutral colours, such as white and grey, look right[6]. In the Color section there are three ways to do it:

• the Auto button sets the white balance for this photo, and when one strong colour dominates it, such as the brown of wood or the orange of a sunset, it keeps most of that colour;
• Eyedropper: click it, then click something in the photo that is actually white or grey, such as a sheet of paper, a wall or a cloud. The editor removes the cast, and the Esc key turns the eyedropper off. If the spot you click is too dark or the white is blown out, the editor asks you to pick another light grey spot;
• the Temperature and Tint sliders: Temperature shifts the colours between blue and yellow, and Tint between green and magenta.

The Vibrance and Saturation sliders change how strong the colours are. Saturation boosts every colour equally. Vibrance boosts muted colours more than ones that are already intense, and skin tones less, so faces stay natural.

The Color mixer section changes only the colour you pick and leaves the rest of the photo alone. At the top of the section you choose what to change: Hue shifts the shade of a colour, Saturation changes its strength, and Luminance makes it lighter or darker. Below that are eight sliders, one per colour band: Red, Orange, Yellow, Green, Aqua, Blue, Purple and Magenta. For a deeper blue sky, choose Luminance and move the Blue slider to the left. To make grass less vivid, choose Saturation and move the Green slider to the left.

The Black & white switch in the same section turns the photo black and white. The luminance sliders then decide how light each colour comes out: darkening the Blue band gives a darker sky, and lightening the Orange band gives lighter skin in a portrait.

The Detail section has four sliders. Sharpening brings out edges, and Noise reduction smooths the fine grain you see in photos taken in low light; both run from 0 to 100. Texture strengthens or softens fine detail, such as the texture of skin, fabric or bark. Clarity changes the contrast of larger shapes in the midtones, which makes the photo look crisper or softer.

Sharpening and noise reduction work on the original’s pixels, so on the scaled-down preview of the whole photo they look different from the saved file. You’ll judge them best at 100% zoom, which shows one photo pixel per screen pixel.

The zoom buttons are in the bottom right corner of the photo. Fit shows the whole photo on screen, and 100% shows the real pixels from the full resolution. The Z key switches between these two views. The Zoom in and Zoom out buttons and the + and - keys change the zoom by one step: 25%, 50%, 100%, 200%, 400% or 800%. The preview at 100% matches the saved file: our automated test compares them pixel by pixel at different settings, including RAW files opened at 16 bits, and finds no difference greater than 2 brightness levels out of 255. After a photo is rotated, the difference on sharp edges goes up to 3 levels.

A vignette is a darkening of the edges of the frame. In a lens it’s usually a flaw, but photographers sometimes add it on purpose to draw attention to the centre of the picture[7]. In the Effects section, the Vignette slider darkens the edges when you move it to the left and lightens them when you move it to the right. Once the vignette is on, the Size, Feather, Roundness, Horizontal position and Vertical position sliders appear. You can also move the vignette by dragging the Vignette center point on the photo or with the arrow keys. The Grain slider in the same section adds fine grain, like a photo shot on film.

The Color grading section gives the shadows and highlights a tint without changing the photo’s brightness. You pick the tint with the Shadows hue and Highlights hue sliders, set its strength with Shadows saturation and Highlights saturation, and the Balance slider moves the boundary between shadows and highlights. By default the shadows hue is set to a cool blue and the highlights hue to a warm orange, so raising both saturation sliders is enough for the film look of cool shadows and warm highlights. The shadows hue tints skin tones less, so a face in the shade changes colour less than the background.

Above the sections on the right is the Histogram, a chart of how many pixels there are at each brightness, from the darkest on the left to the brightest on the right. It updates live as you move any slider. When at least 0.1% of the photo is blown out, meaning at least one colour has hit its maximum and the detail is gone, a note appears under the histogram, for example Blown out: 2.4%.

The Show clipping button, the icon next to the Histogram label (J key), marks blown-out areas on the photo in red and completely black ones in blue. That way you can see straight away whether brightening the photo has wiped out detail in the clouds or on a white shirt. To compare the result with the original, hold down the Original button on the top bar or the \ key. Let go to see your version again.

Click Before and after on the top bar, next to the Original button, or press Y. A vertical line appears on the preview: to its left you see the unedited photo, and to its right the photo with your changes. The labels Before and After sit in the top corners.

You can drag the line with your mouse or finger. With the keyboard, press Tab to reach its handle, the Before and after divider slider, and then move the line with the arrow keys. The arrow keys don’t switch photos while the handle is selected. The line stays in the same place on screen when you zoom in, move the photo or go to the next one, even from a landscape photo to a portrait one. Both sides of the line have the same crop and straightening.

The comparison is off in Crop mode: the button is greyed out, and the Y key does nothing. When you go back to editing, the line comes back. Holding the Original button shows the whole unedited photo even while the comparison is on, and you turn the comparison off by clicking Before and after again or pressing Y. The comparison doesn’t change anything in the photo, so the saved file and the histogram ignore it. For the same reason, it also works in a tab that’s only viewing work opened in another tab.

On screens narrower than 640 px, the Original, Before and after and Save buttons show icons only, so the bar fits without scrolling from a width of 360 px. Screen readers still read out their names.

The Undo button on the top bar or Ctrl+Z undoes your last change, and Redo or Ctrl+Shift+Z (or Ctrl+Y) brings it back.

The History panel on the left lists every step under a clear name, such as Exposure +0.50, Crop or Filter: Summer. Clicking any step takes the photo back to how it was at that moment. Several moves of the same slider within 1.5 s count as one step, so small tweaks don’t flood the history. The history keeps 200 steps, and after you close the tab at most 100 of them remain: the first step, Opened, and the last 99.

The Filters panel on the left has 100 filters in twelve categories: Basic (6), Color (10), Portrait (7), Landscape (7), Black & white (11), Film (10), Vintage & retro (11), Cinematic (10), Night & city (5), Neon & futuristic (10), Artistic (8) and Dreamy (5). Each category has a tile with a thumbnail of your photo in one of its filters. Clicking a tile opens the category, and the All categories button or the Esc key takes you back to the list. The filter thumbnails are rendered from your own photo, and hovering over a filter shows it on the large preview before anything changes. A click applies the filter. Each filter first sets the light and white balance the same way as the Auto buttons in the Light and Color sections, and then adds its own look. If a ready-made filter would blow out part of the photo, the editor moves the Whites slider to the left, and the Exposure slider too if needed, only as far as necessary. The Filter strength slider weakens or strengthens the filter, from 0 to 150%.

The filters in the Neon & futuristic and Artistic categories change the look of a photo dramatically. Some filters in these and a few other categories add an effect you can’t set with the sliders, for example colours like those of a thermal camera, a glow around bright areas, red and blue fringes along edges, or horizontal lines like on an old TV screen. The Color grading section then shows a reminder about the effect, and that section’s Reset button removes it together with the colour grading.

You can save your own look with the Save the current look as a filter button. The filter remembers the light, colour, the Texture and Clarity sliders, colour grading, effects and colour mixer, while sharpening, noise reduction and the crop stay with each photo. Your own filters appear in the My filters category, where you can delete any of them. The Download my filters button saves them to a file, and Load filters from a file brings them back on another computer or in another browser. In a private window, the browser doesn’t let you save a filter permanently: it works until you close the tab, and the editor suggests downloading your filters to a file.

Your photos never leave your browser. Helios opens, edits and saves them on your device, so no file is sent to a server, not even for a moment.

Cameras and phones store Exif data in each photo: the camera model, shooting settings such as shutter speed, aperture and ISO, the date the photo was taken and often the GPS coordinates of where it was taken[8]. The Keep camera data (without location) option in the save window is on by default. It copies the camera model, lens, date and shooting settings to the new file, and it always removes the GPS location, the camera and lens serial numbers and the manufacturer’s own data (MakerNote). With this option turned off, the saved file contains no camera data or GPS location.

If you only want to remove the location from a photo before sending it on, open it in Helios and save it without changing anything. The new file keeps the date and camera settings but has no GPS coordinates. A JPG is re-saved in the process, at 95% quality with the Full quality purpose, so if every detail matters, choose PNG or TIFF as the format.

Every change is saved automatically in your browser, along with a copy of the original. When you come back to Helios in the same browser, the editor shows Pick up where you left off with the number of photos and the date of the last change. Continue editing brings your work back, and Start over deletes the saved work and opens an empty editor.

This copy only lives in the website data in your browser, so it disappears when you clear your browsing data. Safari deletes a website’s data after 7 days of browser use without a visit to that website[9], so with your first photo in Safari the editor warns you about this once. In a private window, the browser doesn’t let your work be saved, so the editor works but your changes are lost when you close the tab. If the browser runs out of space for a copy of a large original, your settings are still saved, and after you close the tab you only need to open that file again to get your edit back.

To keep your settings longer or move them to another computer, save them to a file. The Download settings button on the top bar saves the settings of all open photos, and Load settings restores them to photos with the same name and file size. The message after loading tells you how many photos the settings applied to and which photos from the file are missing.

If you open Helios in two tabs, only one of them edits. The other shows a message that the editor is open in another tab and you can only view it there, with a Work in this tab button. That button takes over editing, along with the latest change from the other tab. When the tab that’s editing is closed, the next one takes over.