7D Experiment

Please would anyone who is having issues with IQ on their 7D try something for me.

Try taking similar pictures in large, medium and small RAW.

I have had issues with mine and I just happened to notice that the smaller the fike, the sharper the picture tends to be.

can you post some shots showing this?

Oggy1 wrote in post #13360379
I have had issues with mine and I just happened to notice that the smaller the fike, the sharper the picture tends to be.

It looks sharper based on viewing how?

In equal sized prints?

At 1:1 views on the monitor?

At full image views on the monitor?

Realize that sharpening is fundamentally an output size specific action, and so you may get an image that is sharpened more appropriately for monitor display if you generate a smaller jpeg in the camera.

Also make sure to understand that 1:1 views of different pixel count images will fundamentally be views of very different sizes. It's like comparing a 4x6 print to a poster.

Sorry - I should have said. I was viewing both as full screen in DPP and at 100%.

Of course a downsampled image will appear sharper at 100%. no tests need to be done on this.

Look at the logic of what you're saying. It equates to this - "When I enlarge the picture it becomes softer." Is this a surprise? Viewing a smaller file at 100% is viewing the picture smaller - 100% is not an absolute measure.

I weston I wrote in post #13360549
Of course a downsampled image will appear sharper at 100%. no tests need to be done on this.

Yes, but it is the extent that surprises me. There is no way I can get an acceptably sharp picture in large RAW, whereas pictures in medium and small are quite acceptable.

Madweasel wrote in post #13361463
Look at the logic of what you're saying. It equates to this - "When I enlarge the picture it becomes softer." Is this a surprise? Viewing a smaller file at 100% is viewing the picture smaller - 100% is not an absolute measure.

Er - back to front. You have to enlarge a small image with less pixels to make it the same size as a large picture, but in my case I am still getting better results from the small picture.

Oggy1 wrote in post #13362115
Yes, but it is the extent that surprises me. There is no way I can get an acceptably sharp picture in large RAW, whereas pictures in medium and small are quite acceptable.

Huh?

It's probably my ESL at work here, but how does the above make any sense?

You have a lens. You have an image circle that passes through the lens and hits the same sensor. Whatever photons hit the sensor will be captured by that same sensor.

Given the same output (at the smallest resolution since you don't want to introduce any fake pixels by upsizing), the photos should look identical.

Whatever sharpness you think you've gained is because DPP is applying the sharpness from you picture style setting to a smaller photo. Sharpening a smaller resolution photo will always make the results more pronounced than sharpening a higher resolution photo.

I'd suggest you take a look at this thread https://photography-on-the.net/forum/showthre​ad.php?t=799284 and see how your RAW images compare at 100%. If they are significantly softer after appropriate post processing, including sharpening, then let us know.

If you print a 8x10 of a small raw and a full sized raw they will both have the same sharpness. If you print a poster size small raw vs a large raw, your small raw will look like ****....

A full size RAW image appropriately downsized to M or S-RAW will be sharper.

Oggy1 wrote in post #13362115
There is no way I can get an acceptably sharp picture in large RAW, whereas pictures in medium and small are quite acceptable.

Sounds like you have technique issues.

My wife likes to show me her awesome pictures on her little point and shoot all the time... they look great on that tiny little monitor and when we look at them at home on my computer, they suffer. You're missing the point about how downsizing affects apparent sharpness.

svarley wrote in post #13362384
Sounds like you have technique issues.

+1

Getting a tack sharp pixel level shot out of a 7D isnt easy and requires good technique and good optics.

100%crops are a great tool to use; but you have to learn how to read them in order to understand them.

First up if you have shots with different MP values, but with the same sensor size, and then view them at 100% the larger MP shots will be shown far larger than the lower MP ones. That is because each pixel has the same unit of space on the screen, but a higher MP shot has more pixels on each axis - therefore an 8mp and 18mp photo will show up very differently, with the 18mp appearing far far larger on the screen at 100% view than the 8mp.

This means that when you compare them the larger MP shot is effectively being seen at an enlarged scale to the smaller MP photo; therefore sharpness may well appear less because you're viewing the details at a much higher magnification. In addition shake is also more critical and you might well find that (for 100% crop views) you'd need a faster than normal shot to eliminate handshake from the shot (because magnifcation increases how much of the shake you can see).

HOWever - 100% crops are not the end of the world and its in resizing for proper output use that you really see the differences in performance. Remembering that resizing requires sharpening both before and after the process and that different outputs have different demands on sharpening to give the best appearance.
Therefore whilst your 18MP shots might look softer at 100% compared to the medium and small scaled ones; once you resize and sharpen your 18MP shot it should be as good (if no better). Try it yourself by resizing your LRAW shots down to the same dimensions as your M and S (remembering to include corrective sharpening).

I don't know the settings on your computer monitor, but if I view a full size RAW file from one of my 7Ds on my monitor at 100% it's equivalent to looking at the image printed 4 and 1/2 feet wide (54") from a distance of approx. 18 inches.

Viewing distance remains the same in all cases, but with M-RAW it's same as if the image were printed 3 and 1/3 feet wide (40.5"). And at S-RAW resolution, it's as if the image were printed 2 and 1/4 feet wide (27").

So it's to be expected, that the highest resolution image will be the least sharp. Viewing each of them at 100% you are actually being 33% more critical of the RAW file, compared to the M-RAW... and fully twice as critical of the RAW comparing it to the S-RAW file.

Do a test yourself... Take three shots of the exact same subject... Preferably something with lots of fine detail. Make one at full RAW, the next as M-RAW, and the third at S-RAW. Now mnimally process each of the files exactly the same way, crop them all 50% (or so, just be sure to do the exact same crop on each) and print the resulting iamges all the same size on smooth matte paper. Compare those side by side. Prints made at the same size give you a much better idea of what the camera is capturing, than trying to compare on screen. And prints will give you much better evaluation, of actual image sharpness and detail.

7D does use a fairly strong Anti-Alias filter. I find I need to apply significantly more sharpening to bring out fine detail with the files from 18MP 7D, than I do with 50D (15MP) or 5DII (21MP) images. Both the latter appear to have much weaker AA filters.

The reason an AA filter is needed over a digital camera's sensor is to prevent en effect called "moire". That occurs when a pattern in the image sort of syncs with the pattern of the pixel array on the sensor, and causes whacky artifacts and effects. Google for "moire" and you'll see some examples.

7D needs a stronger AA filter than earlier cameras, because it uses one of the densest or most crowded sensors of any DSLR. It's got close to 54,000 pixels per square millimeter. For comparison, 50D has just over 45,000 (about 16% less), 40D has a little less than 31,000 (about 42% less) and the full frame 5DII has just over 24,000 (nearly 65% less crowded).

Exactly how much additional sharpening is necessary varies depending upon the final output or use of the image... But I'd estimate I use 50% to 70% more pretty regularly. (Less for small, low resolution images on the Internet... more for large prints, for example.)

The fine detail, and all the apparent "sharpness" that comes with fine detail and micro-contrast, is there... You just have to sharpen the files from the 18MP cameras more to bring it out.

To some degree, too, the very high density of the 7D's sensor can show up any flaws in lenses. You might say it demands better glass. This is true of any higher resolution camera. At some point as they become more and more dense with pixels, a sensor might be able to resolve more than a lens. Better lenses resolve more detail and will be a better match with higher resolution cameras. All three of your lenses are pretty highly regarded though... especially the 300/4 and 15-85.

You might want to do Micro Focus adjust for each of them on your particular camera. This dials in the focus of the lens to be as accurate as possible.

After doing that, shoot some more test shots with each of your lenses. Shoot a series of shots at different apertures and focal lengths, to learn each lens' optimal performance. Most zooms have better and worse focal lengths... For example you will likely find your 100-400mm is not as sharp at focal lengths out near 400mm. 7D at full RAW will show up any lens weaknesses more than a lower resolution RAW file, whether from another lower resolution camera or with 7D M-RAW or S-RAW.

And, most lenses are better stopped down a bit, to a middle aperture. They can be soft at their largest apertures.... and at their smallest smaller.

Diffraction is another factor, that occurs with smaller apertures. The size of the sensor and it's density are key factors here... For example diffraction starts to set in on the APS-C and 18MP 7D at f7.1... that's the camera's "Diffraction Limited Aperture" (DLA). Stop down more than that and smaller apertures will increasingly rob fine detail from the image, making it appear "soft" at high magnification. You probably won't notice it at f8, but will start to see a little if you look closely at f11, and it will be more obvious at f16 and probably pretty bad at f22. You have to balance the need for increased depth of field against any loss caused by diffraction.

For comparison, the DLA for full frame, 21MP 5DII is about f10. It's also about f10 for an APS-C 10MP 40D.

Once again, it might be useful to run some test shots with your camera at different appertures, to see and learn how diffraction effects the images. Just run a series of shots of a highly detailed subject (a weathered wood fence is a good target) from around f5.6 through the full stops down to f22, then inspect the images at higher magnification to see what happens.

Our job as photographers is to be aware of all these factors, and the specific idiosyncracies of each piece of gear we use, then work to optimize it, get the best results possible for any particular image we want to make. There's always compromise, balancing depth of field against diffraction, high ISO noise against adequate shutter speed, etc., etc. We have to adjust how we use our gear and even how we post-process our images, for different situation.

Sharpness alone isn't the only factor with images. In fact, it's not always desirable for an image to be "so sharp it makes your eyes bleed". Most older women do not appreciate portraits that show every little fine detail, for example.

But sharpness is often what people focus on (pun intended) and fret about, because it's one of the easiest nits to pick in your images.