Both devices will be available on a total of five plans each, all over 24 months. Plans range from the entry level $35 Optus My Plan to the top $100 My Plan.
Only the most expensive $100 My Plan does not attract a monthly handset repayment for both the Xperia Z1 and the Xperia Z Ultra.
Optus appears to be heavily pushing the $80 My Plan for both devices. It comes with a $3 per month handset repayment when paired with the Xperia Z1 ($83 per month), and a $5 per month repayment with the Xperia Z Ultra ($85 per month).
The plan includes 800 minutes of standard national voice calls, unlimited standard SMS and MMS messages to Australian mobiles, and 2GB of data per month.
The Optus plans follow the telcos new charging model, which it announced back in June. Under the new model, customers have the option to change plans on a monthly basis if they exceed their data or voice allowance.
Optus also quotes voice inclusions by minutes rather than a traditional dollar value.
Optus says pre-orders for both the Xperia Z1 and the Xperia Z Ultra will be delivered from Tuesday, 1 October, provided the order is placed by Saturday, 28 September.
The waterproof and dust-resistant Xperia Z1 has a huge emphasis on photography, boasting a 20-megapixel camera and a "G Lens" that claims to work better in low light conditions. The camera includes a 27mm wide angle, an f2.0 aperture, and a 1/2.3-type CMOS image sensor.
The Xperia Z Ultra is a 6.4in smartphone that will compete with Samsung's upcoming Galaxy Note 3. Sony claims the device is the world's slimmest smartphone with a full HD display, measuring just 6.5mm thick.
Both the Xperia Z1 and the Xperia Z Ultra are available in black, white, and purple colour variants, but Optus will only offer the black model.
Optus' full pricing for both the Xperia Z1 and the Xperia Z Ultra can be seen below.