Dp3 Merrill Macro Focus Issues: Am I a dingus?

Started 7 months ago | Questions
16GreenBeans
OP 16GreenBeans Forum Member • Posts: 70
Re: Dp3 Merrill Macro Focus Issues: Am I a dingus?

D Cox wrote:

Stop down more. I generally use f/11, f/13 or f/16 for macro on the DP3M.

Check your alignment more carefully. A copy stand is easier to level than a tripod. I use a spirit level that's about 3 inches (75mm) long.

Is your subject really flat ? Are you using a close-up lens ?

Don Cox

Hey Don,

For clarification, I am not using any macro/close up lens filters and am only using a tripod with a built in spirit level. The test shots below were done with each book flat against a wall.

This photo was taken at f16. To my eyes, there does still appear to be some hazy corners, which might be normal (I'm fairly new to macro work).

f16 Test

Here at the righthand corners and bottom left corner.

f8

And here at each corner as well.

f8

At this point, I'm starting to believe the overall lack of corner sharpness is either due to my own inexperience or just a normal part of macro work.

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xpatUSA
xpatUSA Forum Pro • Posts: 21,414
Re: This is not a good test image

brendanpaxton wrote:

xpatUSA wrote:

brendanpaxton wrote:

DavidWright2010 wrote:

brendanpaxton wrote:

DavidWright2010 wrote:

exposure of 0.6 seconds? Anything could go wrong. And it looks blurred all over.

David

Nothing wrong with 0.6 sec, We were told the camera is on a tripod (and there is clearly no motion blur in the image).

Here's a 400% crop from the center .It certainly looks blurry to me:

David

Anything will look blurry at 400% crop.

I disagree.

David's zoom above is not smoothed; therefore the blur is in the capture and was not caused by the 400% zoom.

Creating pixels out of thin air where there were none (zooming to 4x the data's resolution, i.e. upscaling by 4x) requires extrapolation of data.

David's zoom was not smoothed. It was upscaled Nearest Neighbor.

The result will always appear blurred.

Nope.

Blurring (i.e. averaging of neighboring points) is inherent to any interpolation or extrapolation process.

When up-scaling Nearest Neighbor by integer values 1x, 2x, 3x ... etc, there is no interpolation. At 400%, each original pixel just becomes a 4x4 pixel.

For example, a one-pixel cross-hatch (see middle):

Becomes a pure cross-hatch even at very high zoom:

No blur at all ... agreed?

The OP's image is sharp in the bottom of the frame. And there is no >>motion<< blur in the image.

I did not comment about the OP's image, only David's blur due to zooming 400%, i.e. none.

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jande9
jande9 Senior Member • Posts: 1,663
Re: Dp3 Merrill Macro Focus Issues: Am I a dingus?
1

I would assume that the lens on the DP3M is a curved field lens, suitable for general photography.

For edge to edge sharpness shooting flat surfaces you need to use a flat field lens.  Apparently most true macro lenses are flat field which makes them suitable for shooting documents and art.  I don't own a macro lens so I don't have any personal experience with this.

Jan

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xpatUSA
xpatUSA Forum Pro • Posts: 21,414
Re: Dp3 Merrill Macro Focus Issues: Am I a dingus?

jande9 wrote:

I would assume that the lens on the DP3M is a curved field lens, suitable for general photography.

For edge to edge sharpness shooting flat surfaces you need to use a flat field lens. Apparently most true macro lenses are flat field which makes them suitable for shooting documents and art.

Good news for GB though, because his DP3M becomes no different than anyone else's.

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16GreenBeans
OP 16GreenBeans Forum Member • Posts: 70
Re: Dp3 Merrill Macro Focus Issues: Am I a dingus?

jande9 wrote:

I would assume that the lens on the DP3M is a curved field lens, suitable for general photography.

For edge to edge sharpness shooting flat surfaces you need to use a flat field lens. Apparently most true macro lenses are flat field which makes them suitable for shooting documents and art. I don't own a macro lens so I don't have any personal experience with this.

Jan

Hey Jan,

That's a really interesting observation and one I had no idea existed! Most likely, that's the reason behind my focusing issues.

Now I just have to see if there's some kind of tool or filter to try and compensate for the curved lens.

Thanks for your help!

GB.

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D Cox Forum Pro • Posts: 31,072
Re: Dp3 Merrill Macro Focus Issues: Am I a dingus?

16GreenBeans wrote:

jande9 wrote:

I would assume that the lens on the DP3M is a curved field lens, suitable for general photography.

For edge to edge sharpness shooting flat surfaces you need to use a flat field lens. Apparently most true macro lenses are flat field which makes them suitable for shooting documents and art. I don't own a macro lens so I don't have any personal experience with this.

Jan

Hey Jan,

That's a really interesting observation and one I had no idea existed! Most likely, that's the reason behind my focusing issues.

Now I just have to see if there's some kind of tool or filter to try and compensate for the curved lens.

Thanks for your help!

GB.

Just stop down more. My DP3M images taken at f/13 or f/16 are sharp all over.

You could also try manual focus with focus stacking, but that's rather laborious.

Don

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D Cox Forum Pro • Posts: 31,072
Re: Dp3 Merrill Macro Focus Issues: Am I a dingus?
1

jande9 wrote:

I would assume that the lens on the DP3M is a curved field lens, suitable for general photography.

Field curvature will vary with distance. It's quite likely that the DP3M lens has its flattest field at a distance such as 10 metres.

A macro lens or enlarger lens may have its flattest field at around 1/10 life size -- that is, where a 10 inch high subject comes out at one inch high on the sensor -- or conversely, a one inch high negative makes a print ten inches high. An ordinary lens will be flattest at a greater distance. For astronomy, you want a flat field at infinity, but this is too far for everyday photography.

Some macro lenses have internal floating elements which move slightly to adjust the field curvature at various distances, I don't think the DP3M lens has this.

The cure for field curvature is to stop the lens down. Then experiment with various settings of Sharpness in SPP to see if you can get the best balance between the slight blur from diffraction and the halos caused by sharpening. For instance, instead of -2.0 one might prefer -1.6.

Another thing to try is setting the focus point about half way between the centre and the corner. (Page 50 in the manual.) Don't forget to set it back to centre when you've finished doing flat field macro.

For edge to edge sharpness shooting flat surfaces you need to use a flat field lens. Apparently most true macro lenses are flat field which makes them suitable for shooting documents and art. I don't own a macro lens so I don't have any personal experience with this.

Jan

Don Cox

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D Cox Forum Pro • Posts: 31,072
Re: Dp3 Merrill Macro Focus Issues: Am I a dingus?
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xpatUSA
xpatUSA Forum Pro • Posts: 21,414
Re: Dp3 Merrill Macro Focus Issues: Am I a dingus?

D Cox wrote:

See also here:

https://photographylife.com/what-is-field-curvature

Thanks for that. I hadn't related the standard lens MTF chart to field curvature ... we live and learn!

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D Cox Forum Pro • Posts: 31,072
Re: Dp3 Merrill Macro Focus Issues: Am I a dingus?
2

xpatUSA wrote:

D Cox wrote:

See also here:

https://photographylife.com/what-is-field-curvature

Thanks for that. I hadn't related the standard lens MTF chart to field curvature ... we live and learn!

As with the Red Queen, it takes all the learning one can do to stay at the same position of ignorance.  

Don

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Sigma fp
DavidWright2010 Veteran Member • Posts: 3,255
Re: Dp3 Merrill Macro Focus Issues: Am I a dingus?

This has been mentioned before, but a handy way to quickly find the focal plane is with the PS tool Filter | Stylize | find edges:

So I shot a bit of house siding with my DP3M, at a distance of about a foot:

The red circle is roughly where I focused, and you can clearly see the ring of best focus. (It looks like I wasn't exactly  parallel to the surface, since the ring is lighter at the bottom.)

David

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DavidWright2010 Veteran Member • Posts: 3,255
Re: Dp3 Merrill Macro Focus Issues: Am I a dingus?
1

D Cox wrote:

You could also try manual focus with focus stacking, but that's rather laborious.

Don

I was going to mention that. I've done dozens of focus stacked images, and yes it can be tedious, esp. when your technique is not quite right. I usually shoot them at f/5 or so, and take maybe 20 images using a rail. The benefit is that everything you want to be in focus is in focus, and everything  else is OOF:

David

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D Cox Forum Pro • Posts: 31,072
Re: Dp3 Merrill Macro Focus Issues: Am I a dingus?

Good point about Find Edges. I'd forgotten that trick.

Here it is applied to the original post:

I think it would be clearer if Mr GreenBeans applied it to the original TIF from SPP. Some sharpness will have been lost by conversion to JPG and then to DPR-JPG.

Don

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xpatUSA
xpatUSA Forum Pro • Posts: 21,414
Re: Dp3 Merrill Macro Focus Issues: Am I a dingus?

DavidWright2010 wrote:

This has been mentioned before, but a handy way to quickly find the focal plane is with the PS tool Filter | Stylize | find edges:

So I shot a bit of house siding with my DP3M, at a distance of about a foot:

The red circle is roughly where I focused, and you can clearly see the ring of best focus. (It looks like I wasn't exactly parallel to the surface, since the ring is lighter at the bottom.)

David

Excellent job, David.

The GIMP has the same function with several methods to choose from.

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rick decker
MOD rick decker Forum Pro • Posts: 18,446
Re: Dp3 Merrill Macro Focus Issues: Am I a dingus?

I think the 2nd one looks very good and a little better than the first. The focus may be a hair off on the first. How close to minimum focus were you. There is consisency across the flelds. Here is a shot of a 12 inch subject. I will do a minimum-focus sample later today when I get some time. I don't think you have a problem with your camera at this point although I have not read the rest of the repsonses yet. ONe thing about DPR is that I feel the image loses a little when displayed by them although I can't explain why.

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xpatUSA
xpatUSA Forum Pro • Posts: 21,414
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16GreenBeans
OP 16GreenBeans Forum Member • Posts: 70
Re: Dp3 Merrill Macro Focus Issues: Am I a dingus?

DavidWright2010 wrote:

This has been mentioned before, but a handy way to quickly find the focal plane is with the PS tool Filter | Stylize | find edges:

So I shot a bit of house siding with my DP3M, at a distance of about a foot:

The red circle is roughly where I focused, and you can clearly see the ring of best focus. (It looks like I wasn't exactly parallel to the surface, since the ring is lighter at the bottom.)

David

Hey David,

That's a really neat trick there. It looks like GIMP has a similar feature so I will definitely test it out.

GB.

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xpatUSA
xpatUSA Forum Pro • Posts: 21,414
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