Lens Experts - - Can you tell the difference ?

Sigma 24-70mm f/2.8 EX DG Macro for Nikon

07/02/2006 10:08:01 PM · #1

Folks
I need a bit of advice and assistance from people who have done some of their own analysise of lenses.

After much deliberation (and postings on various forums) I purchased a Tamron SP f2.8 28-75mm lens. I took it out for a test run on Saturday and when I looked at the shots I thought they seemed to lose a bit of detail. I have never had a "good" lens before - so I don't know whether my expectations are unrealistic.

I decided to do a comparison test with the Canon kit lens (18-55). To try to sort out sharpness I set up a shot of newspaper, so I could zoom in on the detail of the print. I don't really know what I'm doing but this seemed a reasonable approach.
I set it up on a tripod and took 5 shots with each lens (f5.6, f7.1, f8, f10, f16) on AV with fill in flash (hopfully making the lighting equal).
When I examined the shots in Photoshop (magnifying to 200%) - it looked to my untrained eye that the kit lens was sharper !!
Could anyone who is a little more knowledgable than myself have a look at these shots and give their opinion. If this is the case then I assume I have a faulty lens and will need to exchange it. I assume that the Tamron being an SP lens should be far superior to the Kit lens.

I have given 4 shots below - but the others are in my Work Folder in my Portfolio. If someone could take the time to examine these and give their opinion I would greatly appreciate it.

cryan

Nikon D700

07/02/2006 10:12:16 PM · #2

after looking at the text on the lens box it looks like the Tamaron is sharper, but not by much.

Canon EF 100-400mm f/4.5-5.6L IS

07/02/2006 10:22:08 PM · #3

I forgot to mention - the canon kit lens was at 35mm and the Tamron at 33mm ( I couldn't get them exactly the same).

awpollard

Canon EOS-5D Mark II

07/02/2006 10:31:21 PM · #4

Tajhad, just curious but what focus mode are you using on your 350? Is it Center AF only or AIAF (Auto Focus Point). The reason I ask is all the shots seem to be sharp on the left, almost like the left zone focal point is the one that is locking.

Edit: Note the Candle holder (sorry can't remember the offical name) on the left in each shot... It seems to be very sharp in every picture.

Message edited by author 2006-07-02 22:54:20.

dwterry

Canon EOS-1D Mark III

Canon EF 24-70mm f/2.8L USM

07/02/2006 10:32:46 PM · #5

One thing to note... your camera will begin to lose definition beyond about f/11 or so. So the f/16 images, although theoretically more in focus, will be softer than your f/8 images (which I think is noticeable in the images you posted).

For more information about diffraction and aperture sizes, click here.

Canon EF 100-400mm f/4.5-5.6L IS

07/02/2006 10:54:11 PM · #6

Andy
The metering mode is Evaluative metering (the default for the 350D) and the Auto focus is to the centre point (automatic setting I assume - it suits me to focus from the centre - I can always lock the focus to reframe)

The red focus point was taken on the womans face on the newspaper.
I noticed you have a Tamron. Does this seem right to you ?

awpollard

Canon EOS-5D Mark II

07/02/2006 11:03:08 PM · #7

Originally posted by Tajhad:

Yes, I was going say that AIAF can produce varying results in all kinds of situations. I tried AIAF once in the year and half I have had my 20D and did not like it. It can produce images that look similar to backfocus, and is real easy to focus in the wrong place.

From what I see in your examples, No it does not seem right for Tammy 28-75mm... I would believe my copy would produce sharper results... I will shoot a similar test.

fotomann_forever

07/02/2006 11:07:59 PM · #8

if you can show a 100% crop of the most focused part of the image it would be more accurate.

DrAchoo

Panasonic Lumix DMC-LX5

Canon EF 24-105mm f/4.0L IS

07/02/2006 11:22:15 PM · #9

Ya, I'm not sure you can tell a ton from a resize sample...

Canon EF 100-400mm f/4.5-5.6L IS

07/02/2006 11:38:12 PM · #10

So what do you need ? A section of the shot, at 100% zoom. Save as a JPEG and resize to 640 ? Or is there another way I can show you ?

fotomann_forever

07/02/2006 11:42:19 PM · #11

yeah, just a section at 100% zoom.

awpollard

Canon EOS-5D Mark II

07/02/2006 11:43:07 PM · #12

Originally posted by Tajhad:

So what do you need ? A section of the shot, at 100% zoom. Save as a JPEG and resize to 640 ? Or is there another way I can show you ?

Open the Originals and do a 640x640 crop of the same place (newspaper) in each one, that would be a Hundred Percent Crop... that way we could compare as it cam out of the camera and has not been resized.

Message edited by author 2006-07-02 23:43:35.

Brad

Olympus OM-D E-M1

Olympus 40-150mm f/2.8 PRO M.Zuiko

07/02/2006 11:43:13 PM · #13

I have both of those lenses and did some comparisons of my own, and can say without a doubt, the Tamron is better overall.
The kit lens is far better than most give it credit for though.

Message edited by author 2006-07-02 23:43:23.

Olympus 40-150mm f/2.8 PRO M.Zuiko

07/03/2006 12:36:41 AM · #14

Andy
I assume you mean a 640 pixels by 640 pixels crop. How do I do this ? When I get the crop tool up - it shows me height and width in cm. I can get 640cm by 640cm but not pixel size. How do I do this (PS CS2)

Brad
I've heard lots of good reports on the Tamron. What I'm trying to work out - is this lens I have faulty or are my expectations wrong. From the shots I posted - do they compare to your results or are they way- different?

Brad

Olympus OM-D E-M1

07/03/2006 12:52:56 AM · #15

Most any lens will yield similar in quality at 640 px and compressed.
What you need to do is to look at a section, 100% and compare, looking in the corners of the image as well as the center. The Tamron will look sharper and have less chromatic aberration (CA) and vignetting, or at least that is what I have found. Landscapes taken with both lenses set to about 30mm, again the Tamron will have sharper details, as the 18-55mm Canon loses a significant amount of detail at very far away/infinity distances.

jmsetzler

Sony Alpha a6000

Sony 16-50mm f/3.5-5.6 E-mount

07/03/2006 12:59:17 AM · #16

What you really need to do to compare lenses is setup the same shot (as you have) and make sure the exposure and lighting are the same (which you haven't). I would take the flash out of the equation, shoot in manual exposure mode and adjsut the shutter speed to compensate for your aperture changes to guarantee that your exposure is the same on each photo. I would also shoot at something 'flat' rather than in 3 dimensional space.

Sony 16-50mm f/3.5-5.6 E-mount

07/03/2006 01:21:39 AM · #17

The exposure was the same for each lens. F16 / 2 sec (f10/0.8; f8/0.5)for both lenses. The flash was used to eliminate any changes in natural light. The only difference was the slight 33mm on the Tamron and 35mm on the Canon.

jmsetzler

Sony Alpha a6000

07/03/2006 02:07:07 AM · #18

Originally posted by Tajhad:

Was your flash in manual mode where you are sure that it was firing at the same power for each photo?

hsteg

Fujifilm X-T20

Canon EF 70-200mm f/2.8L USM

07/03/2006 02:10:34 AM · #19

tammys warmer.

Carl Zeiss 35mm f2.4 Jena/Flektogon MC

07/03/2006 09:31:30 AM · #20

jmsetzler
The flash was used as fill in - using the exposure the light reading gave me. I thought this would make it fairly consistent for both lenses.
I thought this might effect the colour caste or exposure but not the sharpness. Am I looking at the wrong thing ?
The sharpness was the thing I was concerned about - but as I said earlier I have never really had a "good " lens or how to really compare it.
Maybe the lens is fine and I'm barking up the wrong tree. I just thought that you guys who have good lenses would know what to look for and have a comment.
I'll try and shot something flat (would newsprint be the best to judge sharpness ?) and with natural light and post them in the next few days.

Uusilehto

Canon EOS-1D

07/03/2006 10:09:36 AM · #21

Tajhad. Please read this:
//www.kolumbus.fi/uusilehto/websizepics/

EDIT: link'd.

Message edited by author 2006-07-03 10:09:54.

Prof_Fate

07/03/2006 10:52:31 AM · #22

Some things to know BEFORE you do testing...

//www.night-ray.com/comments.php?id=82_0_5_0_C
//visual-vacations.com/Photography/focus-recompose_sucks.htm

So you need to use a tripod and manual focus. The flash will just light things up or affect the color cast, should have no effect on the sharpness issue.

I tried tests like you did and I got mixed results - in other words, the same results you got - as in 'i can't tell the difference'.

SO i did some 'real world' tests - not as scientific and precised, but you know, when i'm out shooting I'm not scientific and precise. I've also found that from the camera you may not see much difference - hit the pics wihta USM of 300% .3 and 0 and then compare at 100% - the center and corners.

Sigma 18-50 at F2.8

At F4

and a 5.6