Testing the Sony SAL75300 and Sony SAL18250 lenses

a57 with 75-300. f/8 @ 1/320th, ISO 800

I have continued to persevere with bird photography now that I have the Sony a57 and SAL75300 lens. On an APS-C sensor that equates to a 450mm equivalent fov (field of view), so I can get reasonably close to the wildlife.

But I can't say that I have been blown away by the performance of the Sony 75-300mm f/4.5-5.6 lens. It's certainly not 'tack' sharp (or even close) at the 300mm end - which is exactly where you want to be if you buy a telephoto lens. 

Case-in-point - the other evening I went back down to my local lagoon and followed a Grey Heron around for about an hour. He slowly became used to my presence, and so I got reasonably close. I managed to get some decent poses, fairly close up, but the light was low, so I had to crank the ISO up (again). I've had to do this on both occasions now and I'm beginning to think that the high ISO's are contributing to the overall 'softness' I'm experiencing with this lens?

Of the 250-ish images I shot of the grey heron, I kept just four. All the rest were just too soft. And the four I kept only just snuck through.

So I decided that on the next sunny day, I was going to go out in the middle of the afternoon, in bright conditions, and test the lens at ISO 100. On a tripod. With a 2 second delay on the shutter. At all focal lengths and apertures. Just to see what this lens is really capable of in a 'best case' scenario. So that's what I did this weekend.

And while I was at it, I thought I'd test the SAL18250 at the same time. Just - ya know - because. So sit back, relax, get a beverage, and lets find out how good(?) these two lenses are...

Greymouth Wharf from Cobden. Sony a57 with SAL75300. f/8 @ 1/250th, ISO 100 (at 135mm)

Looking across to the Greymouth Wharf area from Cobden Lagoon is a great place to do these kinds of telephoto lens tests. First because there's plenty of space to set up your tripod, second because it provides lots of details and contrast to lock in on, and third because it's only five minutes from my house 😆

I set up as outlined above; on a tripod, with 2 second timer, central focus point (yes, I auto-focused because that's what I do 99% of the time in real-world shooting conditions), steady shot off (because I'm on a tripod) and aperture priority mode so I could speed up the process, since I would be working through all the apertures at every focal point marked on the lens barrel. Easy...

After I had all the images, I opened them in Lightroom, looked through each set of f/stops for each focal length I shot at, and chose the sharpest of the set. The lenses 'sweet spot' at that focal length, if you will. Below, are the results.

The selections above are all central crops at 100%, made in Photoshop, with my 'normal' sharpening applied (Unsharp Mask Filter applied at 125%, Raduis 1, Threshold 0). It might be difficult to make out what's happening from a low-res internet image, so I'll just tell you what I found....

The Sony SAL75300 lens (at least my copy of it), is soft at 75mm across the aperture range - with f/16 being somewhat presentable. But this isn't a lens I will be shooting at the 75mm end. Period 

From 100mm through to about 250mm, the lens is what I would call 'acceptably' sharp from f/5.6 to f/11 - with f/8 more than likely being the sweet spot. Images within this aperture and focal range are sharp, without being 'tack' sharp. This lens never really manages tack sharp.

At 300mm there is a fall-off in overall sharpness again, although not as bad as at the 75mm end (where it really is horrendous). At the 300mm focal length, f/5.6 to f/8 is 'reasonably' sharp, but I would stick to the 100 - 250mm range for better performance if I could. The lens has other issues at 300mm as well, exhibiting high levels of purple fringing. This is very evident at f/5.6, becoming better (although not completely gone) at f/8. Even with 'Remove Chromatic Aberrations' ticked in Lightroom's lens correction tab.

I thought that maybe the 16MP sensor of the a57 wasn't doing the SAL75300 any favours, and it may perform better on the full-frame 24MP sensor of the a99? So, of course, I tested this theory as well.

Once again, I'll decipher the low-res findings for you...

Basically, nothing changes. Apart for the fact that the a57 crop sensor is producing a slightly bigger fov for equivalent focal lengths - the actual sharpness remains relatively the same. Yes, the a99 is ever so slightly 'cleaner' (ISO 50 compared to ISO 100), and maybe a hair sharper? Maybe. But nothing that makes it shockingly different.

So bottom line with the Sony 75-300mm f/4.5-5.6 (SAL75300); don't shoot at 75mm (at all), stick between 100-250mm and between f/5.6 to f/11 (let's just call it f/8 shall we?), and you should get 'acceptably' sharp results. Depending, of course, on your idea of 'sharpness'.

Cobden Lagoon. Sony a57 with SAL18250. f/8 @ 1/400th, ISO 100 (at 18mm)

Ok. So having established that the SAL75300 is really a 100-250mm, lets tackle the 18-250mm super zoom shall we!?

The SAL18250 is another one of those lenses that gets a bad rap from some reviewers. Actual users, on the other hand, often have some good things to say about this lens. Let's find out for ourselves.

Same process as above for the 75-300mm lens, although I changed position slightly so that there would be some interesting foreground in the image. Going through the apertures and focal lengths on this lens, what did I find?

Deciphering the above from what I see full-screen on my desktop computer at home, there's some good news if you want to use this lens as a pseudo landscape lens (as I do).

From 18mm up to 70mm, the lens performs very well in terms of sharpness - from f/5.6 to f/11. I wouldn't hesitate to use any combinations of the above. 18mm up to 35mm is even sharp through to f/16, which is a great result for us landscape photographers. Lens correction at the extreme 18mm end works well in Lightroom, and the corners are also nice and sharp. So at the 'wide' end of the lens, I'm very happy.

From 100mm up things change slightly. At 100mm sharpness is good from f/5.6 to f/8, and at 200mm from f/6.3 to f/8. At the extreme telephoto end of 250mm, only f/8 is what I would call 'acceptably' sharp.

So again, the good news for this lens, as a walk-around/travel/do-it-all superzoom, is that if you lock the aperture down at f/8, then practically all your images will be sharp. And if you want to use it as a landscape lens at the wider ends, then you have a great range of f/stops and focal lengths to choose from (up to about 100mm).

All-in-all I think this is a great result, and I'm well pleased with the SAL18250. 

I'm less pleased with the SAL75300, due to the less than impressive performance at 300mm (and 75mm). So does that mean I should just use the SAL18250 for everything and leave the 75-300mm at home?

Actually - no. Because again, based on my testing, the SAL75300 is a decent performer from 100mm to about 250mm. And the SAL18250 is an excellent performer from 18mm to about 100mm. Can you see the synergy here? The 75-300mm picks up where the 18-250mm leaves off. So effectively, with both lenses, I have decent (to sometimes excellent) performance from 18 to 250mm using both lenses. I did, of course test this theory out as well...

Hopefully you can clearly see that the SAL75300 is sharper from 100mm to 250mm than the SAL18250. Which means that it is still worth keeping both lenses, and taking both with me when I go out. If the 75-300mm lens was a big, heavy beast, then I'd think twice about bringing it. But it's not (it's only 460grams).

Am I disappointed with the lenses performance at 300mm? Yes, I am. And if I had the money, I would be changing it for either the Tamron SP 70-300mm f/4-5.6 or the Sony 70-300mm f/4.5-5.6 G SSM lens - both of which would, I believe, be infinitely better.

But I don't (have the money), so the Sony SAL75300, confined to shooting between 100 to 250mm, and from f/5.6 to f/8, will have to do during the meanwhile...

Sorry for the long post - and thanks for sticking with me this far (if you have). But it's a good, and important, exercise to do for yourself if you want to get the best out of your lenses. No matter what they might be. Lens testing doesn't have to be about boring test charts and brick walls. Get out in your natural environment and do some 'real-world' testing. I find this is always the best kind of testing. And the results may surprise, delight, or upset you!? 😄

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UPDATE: 15/04/22

Take all of the above with a grain of salt... 

I have recently discovered that my a57 isn't focusing properly - the sensor is probably out of alignment. So my overall impression of 'softness' is not surprising - and therefore all of the above is probably somewhat invalid!