Nikon 50mm F1.8 vs Nikon 18-55mm F3.5-5.6

[stylam]

I've been using a D90 with a 18-55mm F3.5-5.6 lens for the last year. I recently inherited a Nikon 50mm F1.8 lens and was looking forward to using it, expecting better image quality than the 18-55mm.

I did a trial tonight - see photos below. Both photos were taken with the camera on a tripod, on a timer so I didn't shake the camera by pressing the button. Both were taken at F5.6 (which was wide open on the 18-55mm at 50mm focal length, but stepped down a fair bit on the 50mm F1.8).

Photo below: 18-55mm F3.5-5.6. Taken at 50mm, F5.6





Photo below: 50mm F1.8. Taken at F5.6





I was expecting the image quality to be better from the 50mm F1.8 lens, but was really disappointed. You can clearly see the image from the 50mm is much softer, especially in the centre (very obvious with the text on the boxes). I had to step down to F11 on the 50mm F1.8 before the text is as sharp as the photo taken at F5.6 with the 18-55mm.

Is there something wrong with the 50mm F1.8 lens? Does age of a lens affect the image quality? (I believe the 50mm lens is around 10 years old).

I don't know if it is the F1.8D or not (it doesn't say "D" on the lens) - see photo below, but it hasn't got the push and turn pin either of the predecessor of the "D" lens.





Would appreciate comments please. Was I right in expecting better image quality from the 50mm vs the 18-55mm ?

 

[IPOP]

The 18-55 kit lens is actually a pretty good lens. That would be my only conclusion.

 

[ssh33]

Was I right in expecting better image quality from the 50mm vs the 18-55mm ?

Shoot both at f/2-f2.5 and you will see the difference
--
Serge

 

[nkarasev]

The problem is that you expected the 50mm to deliver the image quality just like this, out of the box, without knowing how to put it to work to use its advantages. Also the camera with this lens may need to have focus adjusted.

First thing - find if it is in fact focusing right, or if it needs focus adjustment.

Second, when focus is checked (and fixed if necessary), do the real scene shooting, not the painted box in the dark room.

The main strength of 50mm against 18-55 would be expected:

• when shooting with fast apertures (which 18-55 does not have)
• image sharpness in the corners wide open
• all of the above when pixel peeping

Remember, the 18-55 is a tough competitor for any lens!

Nik

 

[xsimplyjosh]

How can you SHOOT BOTH at f/2-f/2.5 when the Kit lens's max aperture is f/3.5 at 18mm and f/5.6 at 50-55mm? Think about it ...'

Was I right in expecting better image quality from the 50mm vs the 18-55mm ?

Shoot both at f/2-f2.5 and you will see the difference
--
Serge

--
Josh - D7000 ; Nikon 24-70mm f/2.8G ; SB-900

 

[IPOP]

How can you SHOOT BOTH at f/2-f/2.5 when the Kit lens's max aperture is f/3.5 at 18mm and f/5.6 at 50-55mm? Think about it ...'

Was I right in expecting better image quality from the 50mm vs the 18-55mm ?

Shoot both at f/2-f2.5 and you will see the difference
--
Serge

--
Josh - D7000 ; Nikon 24-70mm f/2.8G ; SB-900

umm...I think that was his point. Things you can do with the 50 that make it stand out against the 18-55.

 

[PHXAZCRAIG]

A couple of things.

1. You might have a bit of front focus on the 50F1.8 in that shot. (Hard to tell, but I'm looking at the shiny area in front of the boxes).

Might be nice to try again, with one box angled (to see focus plane), and the other one 'flat' and used as an autofocus target. Also test using careful manual focus.

Also test using F1.8, simply to see very shallow depth of field, which helps to determine if you have the focus accuracy you expect.

2. You might google 'T-stops'. It's not going to make a practical difference most of the time, but the prime is letting more light through at the same f-stop than the zoom. (As would be expected). Notice how the shot with the prime is a little lighter?

--
Craig
http://www.cjcphoto.net

 

[Neocon]

Yes, the results are surprising. I would do another set-up using the 50mm. This time shoot from f2 through f8. You can check how the lens improvees as you stop down.

 

[Digetydog]

I think you inadvertently change the tilt of the shot. If you look at the top of the box, the space over it is different in each shot.

In addition to changing how the lighting of the subjects, I suspect it threw off the focus on the fixed lens.

Having said that, you are dealing with two kit lenses. By giving up the faster glass, the newer lens offers zoom and VR. In it's sweet spot, the new lens is very good.

 

[Chris De Schepper]

had a look at photozone and the 50mm1.8 should be sharper, so this is surprising.
I would give it another try from a tripod and focus manually.
By the way the Heinz can in the corner is clearly sharper with the 50mm1.8.
I suspect it has to do something with focusing

 

[Leonard Shepherd]

Was I right in expecting better image quality from the 50mm vs the 18-55mm ?

Short answer - the way you tested - no

The reproduction size is too small to show subtle quality differences, at this reproduction size the compact zoom is more than good enough The AF target may prevent less than 100% AF focus accuracy with either lens.

By f8-11 there is unlikely to be a difference in sharpness or resolution - because all lenses are pretty much equal in these respects at these apertures.

With much more demanding technique there is a reasonable chance of seeing a prime advantage at f5.6 - at a bigger enlargement.

The zoom cannot shoot faster than f5.6 at 55mm, and the viewfinder is brighter with the prime attached.

--
Leonard Shepherd

Photography could be easier - if cameras and lenses came with an increase in skill button.

 

[Mannypr]

The lens you present is not the 1.8 D . I have the Nikon 50mm f1.8 D and its totally different from what you are presenting . I believe the lens you have is the non D version which doesn't do distance info to the camera body for proper flash lighting.

As already been said , the Nikon 18-55mm is one tought little zoom lens . I have a copy and the first time I went out with it to see how it performed I was surprise at its color rendition and contrast .

The 1.8 is a very versatile lens which can be used under circumstances where the 18-55 just will not work without a flash. Apart from that it's better for bokeh , gives better visibility threw the viewfinder . Sharpness is important but there are other things in a lens performance which might even be more important then sharpness.

 

[Laslo Varadi]

The first problem I see is that your shutter speed is too low and causes camera shake resulting in blurry image. You need to shoot at 1/50 without VR.

Laslo
http://www.digitalexpressionsphotography.com

 

[wasserball]

Did you manually focus both lens? Then, compare the 100% cropped of some of the details of the boxes. I did a similar comparison with the 18-70mm f3.5-4.5 vs 50mm f1.8D on a D90 and I found the prime was sharper. I also found the 18-70 mm lens is sharper at all focal except 18mm where the 18-55mm f3.5-5.6 VR was the better lens.

 

[wasserball]

BTW, the 18-70mm looks more like a pro lens than the 18-55mm lens.

 

[Leon Obers]

Do use LiveView contrast AF to avoid wrong focus by phase detection AF (back- or front focus issues).
----> LiveView contrast AF is the better focus system.
Do use flash to avoid camera shake.

--
Leon Obers

 

[stylam]

Thanks to everyone for your comments.

I’ve done more trials and can confirm that the AF seems to be out for the 50mm 1.8 lens, as most of you suggested.

Below are some photos - taken outdoors this time to rule out slow shutter speeds as a cause of the problem (by the way, the 18-55 kit lens I have is the non-VR version, so any camera shake is likely to affect both lenses equally).

I repeated the same set up as before – camera on tripod, set on timer to avoid shaking the camera when pressing the button, AF was set on spot mode, aimed at the centre of the box along the bottom edge.

Got the same result as the previous trial – the 18-55 seemed to be sharper at F5.6, while the 50mm was soft and fuzzy at F5.6 (obvious around where the spot AF was aimed at - bottom rows of text on the box).

I then followed Leon Obers’ advice and tried it on LiveView, and the 50mm at F5.6 was very sharp where I had aimed the spot mode AF, even sharper than the 18-55mm lens at F5.6 - this was the result which I had expected.

Below photo taken with 18-55mm F3.5-5.6 lens at 50mm focal length, F5.6:





Below photo taken with 50mm F1.8 lens at F5.6 (AF spot mode):





Below photo taken with 50mm F1.8 lens at F5.6 (LiveView mode):





What I described above is probably not very obvious when looking at these photos from this forum page, but it is quite obvious when looking at the images on a large monitor.

I repeated the test on my 85mm F1.8 prime and there was no problem with the AF – got the same result whether it was in LiveView or not (focussed exactly where I aimed with AF spot mode)

A friend of mine has an old Nikon 24-50mm F3.3-4.5 which is approx 10 years old.. I borrowed it and found the AF to be out as well – but was OK when taken in Live View.

So I have some obvious questions:

1) I really don’t want to be limited to taking photos in LiveView whenever I have the 50mm lens on. I believe the more professional Nikon DSLRs have an “AF fine tune” function, but the D90 doesn’t have this. Does this mean I have to take the 50mm lens to a shop to be adjusted? Or should I get a new 50mm F1.8D instead? (mine is the version before the D)

2) Are older lenses such as my pre-D 50mm F1.8 and my friend’s 24-50mm F3.3-4.5 more prone to this problem? My newer lenses (18-55mm & 85mm F1.8) are both OK.

 

[stylam]

Thought I might upload some cropped photos - should show the difference better. As mentioned in the previous post, AF spot mode was aimed at the centre of the bottom edge of the box. Can see the difference in the bottom rows of the text, as well as the texture of the wall.

Below photo was taken with 50mm lens at F5.6, using AF spot mode. Seems to have focussed at a point further away





Below photo was taken with 50mm lens at F5.6, using LiveView. Seems to have focussed at the exact spot where it was aimed

 

[Leon Obers]

I then followed Leon Obers’ advice and tried it on LiveView, and the 50mm at F5.6 was very sharp where I had aimed the spot mode AF, even sharper than the 18-55mm lens at F5.6 - this was the result which I had expected.

...........

So I have some obvious questions:

1) I really don’t want to be limited to taking photos in LiveView whenever I have the 50mm lens on. I believe the more professional Nikon DSLRs have an “AF fine tune” function, but the D90 doesn’t have this. Does this mean I have to take the 50mm lens to a shop to be adjusted? Or should I get a new 50mm F1.8D instead? (mine is the version before the D)

Calibration of a lens if it can be done, maybe depends to the kind of lens. E.g. some lenses do have a separate group of lenses for focusing. But a 50mm lens is a fixed group of lenses that moves as a complete group to front or back for focus. I doubt it can be fixed. Call Nikon Service if you want to know for sure.

2) Are older lenses such as my pre-D 50mm F1.8 and my friend’s 24-50mm F3.3-4.5 more prone to this problem? My newer lenses (18-55mm & 85mm F1.8) are both OK.

Old lens models are not more prone to these errors as new lenses. It just depends to some optical characteristics / errors as e.g. spherical aberration in combination to the limitations of a phase detection based AF system by working by mirrors and open aperture usage.

The AF fine tune on more professional camera bodies has there function for that. If you have a camera-body including these functions, you don't want to have without anymore. Specially for those occasions that you hit these errors.

--
Leon Obers

 

[milz819]

why do people keep saying "fast aperture"..... the aperture is represented by f stops indicating how much light the lens let's in. if you refer to speed its the shutter speed. not the same thing.