There is a new sheriff in town and its name is Nitro from Gentlemen Coders, the software developer behind RAW Power I wrote about recently. This new application, written from the ground up, is able to take advantage of more of the Apple Core Imaging pipeline and newer technologies in ways that RAW Power (written in 2016) cannot since many of Apple’s technologies and coding language did not exist then. It was easier to start from scratch and code a new RAW processing application. I had the opportunity in the summer of 2024 to beta test a version of the app for iPadOS and iOS and was very impressed with the new, more powerful tools and features available in Nitro. 
With new updates and fixes being rolled out on a regular basis since its release on MacOS, iOS, and iPadOS (one price gives you access to all three versions), Nik Bhatt, the sole designer and coder of Nitro is working hard to make it the best RAW image application on the market. That said, Nitro has features and capabilities not available in any other app. My Number 1 tool/feature request I wanted in RAW Power (if you read my post on RP) was a Brush tool. And not just any Brush tool for local editing, but a Brush tool as powerful and capable and beautifully designed as the one we had in Aperture. 
Aperture Adjustment Brush Tools As Nik was one of the original members of the Aperture team at Apple and had worked on the Aperture Brush tool among other things, I knew he would create a tool worthy of the new capabilities Apple was now using. I did have to get over my love for the Aqua-based 3-D GUI (graphic user interface) that made Aperture so beautiful to work with, since Apple and every other app designer long ago abandoned it for a flatter, more pragmatic interface. One aspect I loved the most about the Aperture Brush was the ability to paint in a mask and choose to have the adjustment only affect the highlights, midtones, or shadows within the mask. I thought that was a brilliant feature I’ve never seen in any other Brush tool. 
Working on the iPadOS version of Nitro brings up this little Note when you click the Brush tool. I like that added reminder, as the Apple Pencil is a much more subtle tool to precisely paint masks than my stubby finger! 
You’re given a choice in the type of mask you want to create, and the A.I. versions are very fast and accurate from my experience. But let’s take a look at Brush Masking first.

Once you choose a Brush Mask (or any New Mask) you are asked to name it, which is a good thing if you are creating several masks per image. You can of course be as descriptive with you naming as you like, or keep it simple like here. I like to keep the mask type in the name for clarity’s sake.

 Once a Brush Mask type is set and named, you have a select number of powerful tools which can utilize the masking feature. Not every editing tool in Nitro can use masks (understandabley), but there is a lot that can, and this already makes it far more powerful and useful than the tool in Aperture. One interesting aspect to Nitro’s Brushes is that the adjustment tools available are independent from the same tools in the main edit stack. That is, the Brushes adjustments are tied specifically to the mask. When you go to the main editing tools, they all start at their base point. Think of the main editing tools as “globally applied” adjustments, and some of the same tools as “locally applied” adjustments based on your mask selection, and those same tools work independently from each other. 
You have three selection tabs within Nitro Brushes, the first being the Luma tab which gives you control over the brush Size, Strength, and Softness adjustable with the slider as well as a Detect Edges toggle. By clicking in each box above the slider will adjust the setting. What’s nice here is as you move the slider, the brush size and softness are indicated by a circle within a circle. When you select the Softness box and move the slider left or right you see the inner circle change accordingly. Moving the slider all the way left shows the size of the brush with no inner circle, indicating the brush is a “hard brush.” I like seeing this visual indicator. Very helpful! 
The Colors tab lets you select a color range for your mak to apply to, and using the slider allows for complete adjusting of the affected area even after the mask is drawn. 
By tapping the little box next to the word Color gives you the choice to select a specific color in the image that your mask will apply to. I think Nik designed it this way to give a broader range of use where Aperture allowed the applying of a mask/adjustment to only the Highlights, Midtones, or Shadows of a given masked area. While I always thought Aperture had a brilliant and unique approach to this, I see where Nick’s approach here in Nitro is much better. You can also adjust the Color Range affected with the slider, and again this is adjustable after the mask is applied, and even after closing Nitro, you can re-open the same image and continue editing where you left off. This is why naming and saving the brushes/masks is important as all editing is non-destructive and can be changed later. Well done Nik! 

Finally there is an Intensity tab which lets you adjust the intensity of the mask and the applied adjustments. While I think it would be more helpful for each Adjustment tools to have their own independent Intensity slider so you could apply several adjustments to a single mask and have differing Intensities, rather than a single mask Intensity slider which changes all the adjustments the same way. 
Just as in Aperture, you have a choice in how you see your brush/mask applied as you’re drawing it (or how it is drawn for you if it’s one of the gradients or A.I. assisted masks.) You can access the choices of how to view your mask by clicking the small half-circle icon to the right of the Brush and Erase tools (if you’ve chosen No Overlay, this will appear as a closed circle until you choose an overlay mode.) It’s helpful at least at the beginning to see where the mask is being applied to, but after that, I choose No Mask as I make my adjustments to see what is actually changing as I go. 
While there may be advantages to seeing a mask applied with each of the overlay modes… 

I prefer the Transparen Rubylith one so I can see the image underneath as I go for guidance. Now as to the tools available in mask mode, I’ll touch on one, White Balance: 
The idea that you can take an image and create a mask (brush, gradient, or otherwise)…

Set your overlay to give you good visual clue on the affected are and…

Changing the White Balance on a specific local level blows my mind! We usually think of things like White Balance as a global adjustment. This feature in Nitro lets photographers such as architectural specialists have the ability to custom balance scenes with mixed lighting, or fine art photographers another creative tool for unique looks to an image. 

Choosing the A.I. Subject mask is both fast and accurate from my brief testing. If your entire subject by chance is not fully selected, you can add to it with the brush.

You can also easily invert the A.I. Subject mask to select the background area to be adjusted. You can also add or delete some of the mask using the brush or eraser tool. 
Now while I’ve covered most of the Brush Tool, remember being able to do local adjustments was the single biggest block I had in naming RAW Power my Aperture replacement of choice. But there are so much more powerful features in Nitro that for me push it ahead of Aperture. 
Playing with some extreme adjustments such as the HSL Color adjustment lets you see the parameters built into the tool sets, and how subtle the changes are, and even pushing some to their artistic limits can bring out surprising results. 
A favorite tool for me is what Nitro calls Split Toning, and Aperture called simply Tint (wheels). While Aperture’s version had three tint wheels divided between Black, Gray and White, Nitro has Highlight, Shadow, and Overall, which tones the whole image. I do prefer how Aperture addressed this tool, and even though it’s available as a local brush adjustment, it’s not the same. Minor quibble I’m hoping to get Nik to change 😉. 
I played with the Lens tool, designed for the practical  purpose of correcting lens distortions to intentionally “un-correct” this image and create a warped version, which I have come to quite like! Goes to show, in many programs, you can use tools in ways they were not originally designed for. 
The LUT tool, a feature Nik included in the Beta version from the beginning is another of my favorite and most used tools in Nitro. It is robust and well designed, and allows for user created LUTs to be added to it. I have imported quite a number of my custom LUTs already, and will add more as I create them. I love this particular tool has its own Intensity slider so you can control the level of color grading applied. On some images like the one above, going full on with an already over the top image seems appropriate. 
Nitro comes pre-loaded with a robust set of presets to get you started, as well as built-in LUTs if you don’t have your own. No worries, you are well covered here to get you up and running from the first time you open the app.
The Black & White adjustment tool (which is also available in the Presets tab) has some nice preset filters, and of course I was pleased to see Nik had kept to the Apple Core Image parameters for rendering “proper Black & White settings.” 
Having a Negative<->Positive preset is also a nice nod to those wanting to quickly convert scanned negatives into a positive image for further editing. It’s also fun for creating negative color images from a positive for creative purposes. 
  And lastly in the category of using a tool in unplanned for ways, I experimented with the Channel Mixer, a tool I have never used in any program that has it, either “properly” or here to see what effects it could render. I like the idea of taking a brightly lit color scene and transforming it into a nighttime like image. The possibilities intrigue me. 
With editing choices being nearly limitless depending on your creative imagination, I already have decided that Nitro is my Aperture replacement of choice. That the same program is available on MacOS, iPadOS, and iOS on the iPhone, for one single price for lifetime purchase is fantastic! I will keep my legacy desktop 🖥️ Mac for Aperture use and do one final side-by-side comparison post between Nitro and Aperture once I have upgraded to a new desktop that can take advantage of Nitro’s capabilities. As an early release app, it’s not without its flaws, but as such it is already packed with features (too many to cover in a blog post - go watch the many YouTube videos from Nik), and unique, robust tools that many more mature photo editing softwares either don’t have or implement features in clumsy, crude ways by comparison. Plus I know Nik is working really hard to make it even better, and is listening to customers. That goes a long way towards satisfied customers.