Pixel Peeping Pros: Lens Sharpness?

Started 4 months ago | Discussions
Tilt Fishy New Member • Posts: 2
Pixel Peeping Pros: Lens Sharpness?

Hi fellow photographers,

I have recently upgraded to Sony Alpha ILCE-7 IV + Tamron 28-75mm f2,8 G2, and I'm still learning to master it. Many of my initial photos appears soft and out of focus and I'm in doubt if it is due to the shallow depth of field, and lack of skills, wrong settings etc. - or if the lens is misaligned.

To understand if the lens has issues I looked up a two test in regards to "decentering" and "corner sharpness".

1: For decentering i printed a Zeiss circle chart and manually put the image out of focus to see if the center dot would shift to the sides.

2: For corner sharpness I put the camera on a tripod in uniform lightning and shot jpegs at 4 focal lengths (28mm, 35mm, 50mm and 75mm). All focus lengths at full open aperture (f2.8). I used countdown triggering to avoid bumping the camera.

I did this exercise twice. In the first run i was at 86 centimer distance from the wall. In the second run I was at 25 cm distance from the wall. The images appears softer when I'm closer to the wall, so I tried to lookup the DOF.

To my understanding when I'm at 25 cm distance at 75mm f2.8 the DOP appears to be less than 1mm to each side of the plane. Hence I am a bit in doubt if the longer distance shot (86 cm from the wall) are more representative of corner sharpness than the shorter distance (25 cm from the wall)?

3: For corner sharpness I also tried a sharpness chart printed out in A4, but I had to step very close to cover the full frame at 28mm (approx 15 cm distance from the wall) and I got very bad results. For that reason I didn't' complete this test. Should I have done that instead?

4: Can any of you pixel peeping pros out there help determine if my lens is sharp or not? Any help would be much appreciated, so I can learn if it's me or my gear that needs a fix

Straight out of camera jpegs below - Thank you so much!:

https://drive.google.com/drive/folders/1-Y2lRxQe6A024XgpZmnB75HOcfygsKmu?usp=sharing

Sony a7 IV
If you believe there are incorrect tags, please send us this post using our feedback form.
QuietOC
QuietOC Veteran Member • Posts: 6,690
Re: Pixel Peeping Pros: Lens Sharpness?

I am not seeing problems, but there is not much to judge.

Watch the edges of the chart. It looks like you have the camera tilted to your test surfaces.

Note that JPEG compression throws out high frequency detail. Also it looks like you have sharpness enabled. Turn it down to -3 to disable it.

Using the HDMI output to a big monitor helps getting the camera parallel and combined with magnifier to hit the manual focus.

 QuietOC's gear list:QuietOC's gear list
Pentax Q7 Sony a7R IV NEX-5T Sony a77 II Sony DT 16-50mm F2.8 SSM +107 more
neilt3
neilt3 Senior Member • Posts: 2,874
Need samples and details .
  • 25cm from a wall and less ?

Sounds like the tests your doing are for a macro lens . A macro lens is designed for optimal image quality when used for close up and macro photography.

At 25cm and 15cm distance you can expect the central portion to be reasonable if pixel peeping , but probably not the outer region.

The zoom lens your using is designed for general use of taking photos of things at a distance , it's not a macro lens .

If your going to test for sharpness etc , test under the circumstances the lens was designed to be used on .

Probably set your camera up on a tripod , turn off I/S , and use a remote release , to exclude camera shake from degrading your images for testing .

Holding hand held can endure camera shake and result in blurred images , you need to remove all these issues so your testing your lens and not your ability to hold a camera .

Take shots of a building for eg .

Be aware that at a wide angle setting the lens might be focussed at 20 metres away in the centre of the frame , but the outer edge of the frame might 45metres away from the same wall .

So at a large aperture with thin DOF , the sides of the image will be out of focus , don't confuse this with being blurred due to a fault .

Same goes with your tests at 25cm away from a target .

The image isn't un-sharp , it's just not at the same focus distance as the centre if the frame .

.

What adapter are you using ?

An LA-EA4 or LA-EA5 ?

I assume your adapting an A mount lens on an E mount body , otherwise your posting this question on the wrong forum .

If your using the LA-EA4, then if all the image is not focussed well ( have you tried manually focussing it , again , on a tripod ? ) Then the camera might need the micro focus adjustment looking at in the cameras menu .

Lastly, if your going to post questions on a forum asking what the problem is with the photos your taking , unless you include some sample shots so they can be assessed, how do you expect to get an informed response ?

Make sure it's a large resolution file and EXIF data is included .

I can see you have provided a link to an external drive/site , but I don't click on links from unknown sources . You can post directly on here , and it will include the EXIF needed .

Without knowing how you took the images and the exposure information, we're all just guessing what the problem is .

 neilt3's gear list:neilt3's gear list
Konica Minolta DiMAGE A200 Konica Minolta DiMAGE A2 Minolta DiMAGE 7 Konica Minolta DiMAGE Z5 Minolta DiMAGE 7Hi +66 more
ActionPhotoPassion Senior Member • Posts: 2,691
Re: Pixel Peeping Pros: Lens Sharpness?

It seems to be that you did the test exercise correctly except probably for the distance.

You have to do those test at a distance like if you would normally use the lens.

I can only suggest you to run the very same test with different lenses to be sure.

Question though:

You did took the same shots with AF and in MF to compare the results? It shouldn't have any impact with a mirrorless camera.

-- hide signature --
 ActionPhotoPassion's gear list:ActionPhotoPassion's gear list
Konica Minolta Maxxum 7D Sony SLT-A58 Sony a77 II Sony a99 II Sony a7 +20 more
tbcass
tbcass Forum Pro • Posts: 56,522
Re: Pixel Peeping Pros: Lens Sharpness?

Tilt Fishy wrote:

I did this exercise twice. In the first run i was at 86 centimer distance from the wall. In the second run I was at 25 cm distance from the wall. The images appears softer when I'm closer to the wall, so I tried to lookup the DOF.

To my understanding when I'm at 25 cm distance at 75mm f2.8 the DOP appears to be less than 1mm to each side of the plane.

Something to consider is DOF charts tell you the depth of acceptable focus and not perfect focus. Many of these charts come from the film days and use an 8x10 print. With today's high-resolution sensors and the ease of 100% zoom examination, the visible depth of perfect focus has become extremely small.

I have found this DOF calculator most useful if you click on "show advanced". Since the chart doesn't take 100% zoom of high res sensors into account you have to choose a print size appropriate.

A Flexible Depth of Field Calculator (cambridgeincolour.com)

I find this one pretty good as well.

DOF simulator - Camera depth of field calculator with visual background blur and bokeh simulation.

-- hide signature --

Tom

 tbcass's gear list:tbcass's gear list
Sony RX100 Sony RX10 IV Sony a99 II Tamron SP AF 90mm F/2.8 Di Macro Tamron SP 70-300mm F/4-5.6 Di USD +7 more
Keyboard shortcuts:
FForum MMy threads