Sony a series: My depth of field is TOO shallow…

Quote:

---

Originally Posted by Manfred M

Carefully said, there are a number of underlying assumptions here that impact that rule of thumb. That rule was based on shooting a 35mm camera and making an A4 / 8" x 10" print held 30 cm / 1 foot away.

Change those variables, and that rule of thumb goes right out the window. What variables? Image stabilization, sensor size, final image size and viewing distance.

---

Of course, that's why it's a rule of thumb... ;).

You didn't even mention the physical condition of the user... I know that with at least of my lenses I have no chance to get a sharp image at the "rule of thumb" speed.
And I noticed that the minimum speeds mentioned by OP were at about that shutter speed, makign me think that that could have played a role in th elack of sharpness he sees.

Gosh, thanks everybody for all of this information, and for taking the time to interrogate the images for potential reasons they're not sharp. It's a lot to take on board, and I can't reply to every comment. It seems the biggest things I need to work on are shooting with faster shutter speeds, perhaps ditching the doubler, really drilling down into the Sony AF system (thanks Richard for the link to Mark Galer's YouTube channel), and yes, closing the aperture a bit (or lot) more. Scrutinizing the setting of other nature photographers is definitely something I should be doing more of.

A few notes on those points:
Shutter speed. This is another little frustration I have with my Sony cameras. If I'm shooting in Auto or Av, that camera's AI does a terrible job of picking the shutter speed. It always goes for a slow option, in preference to increasing the ISO. That's partly why a lot of the photos I put up as examples have inappropriately slow shutters. I do try to shoot in Manual as much as possible, it's the only way to avoid the camera defaulting to a slow shutter, or an inappropriately wide aperture. And if I'm feeling lazy put the ISO onto Auto.

The Doubler. The damned doubler. It's disappointing that it does cause such a lost of sharpness, and make attaining a sharp focus harder (see below). It was designed specifically to work with the the 70-200, and does only work with three Sony lenses (the other two were developed after the 70-200). The 70-200 in turn was designed specifically for the alpha series cameras, at which time the a7s ii and a7r ii were the flagships (pre a9 days!). The general consensus is that the Sony 1.4x does give better imagery than the 2x. Video can hide a multitude of sins that you just can't get away with in photos, so I guess that's why I've put up with it for so long. When filming with it, I can only shoot on a heavy, locked-off filming tripod (no centre column here!). Trying to pan with it introduces far too much wobble.

I spent today photographing a diagonal line of AAA batteries, as Grahame and Dan suggested. I tried to standardize things as much as possible. The batteries were on a measured 45 degree angle to the camera, at 2cm intervals. 9 batteries in total, so I could measure the DOF to some extent. I concentrated on the 70-200, as that's the lens that's giving me the most grief, at 70mm and 200mm, with and without the doubler. On the a7s ii and on the a6700. With the camera's sensor 1.5 metres from the center battery, and 3 metres from the center battery. Manually focused on the center battery. On a very heavy tripod, using a 2-second timer delay to fire the shutter. At a selection of apertures, the same selection for every combination. And it did confirm a few things, and teach me a few other things I hadn't really suspected. Here's just one photo as an example: a6400, 3 metres, 400mm, f/10
https://live.staticflickr.com/65535/...e491ebeab1.jpga6400 3metres 400mm F10 by Braydon Moloney, on Flickr

I initially tried to make comparison pages, like the example below. But it was very time consuming, and not giving good results. So I gave up on that, and decided on a table format (keep scrolling down)
https://live.staticflickr.com/65535/...39e34fe3_c.jpgpowerpoint 70mm @ 1.5 metres by Braydon Moloney, on Flickr

Admittedly, this is where things get subjective, as to what's acceptably in focus or not. For the most part, I looked at black line around the 800mAh to determine sharpness. And knowing the distance between batteries, I could roughly say the distance from the front-most battery in focus to the rear-most battery in focus. To me, that's a measurement of the Depth of Field. (I apologize if I'm still not using the term appropriately, but what I measured is what I wanted to measure, and for the sake of simplicity I'm calling it DoF). So, here are my findings, for every combination of lens, camera, focal length, and distance from the focal plane.
https://live.staticflickr.com/65535/...461ec75f_b.jpgDepth of Field table 2 by Braydon Moloney, on Flickr

A few key points:
- the a6400 failed to attain sharp focus at f/2.8 at every combination of variables.
- even the a7s struggled a bit at f/2.8. A number of you have said it's less than ideal to shoot wide open on a long lens; a lesson now learned.
- depth of field increased as I moved away from the subject (which I've read about often, but cool to finally see it in practice)
- depth of field was much reduced when the double was added to the mix.
- at the further distance (3m), the DoF was marginally shallower on the a6400 than the a7s ii - this was more pronounced at wider apertures. This is notable in that it's the smaller sensor, and confirms what was a gut-feeling in my original post.
- while focus can be attained with the a6400 / 70-200 / 2x combo in a controlled testing environment, it's just not capable in the field (refer to the out of focus cockatoo photo). I won't be wasting time with this particular combo in the future.

Thanks everybody for your input and coaching. I will definitely spend some investigating Daniel Parent's Flickr page, thanks Manfred, and attempting to master Sony's AF system. Also, it was interesting to learn that mirrorless cameras aren't ideal for wildlife and sports shooting.

Quote:

---

3. However considering the TYPE of light hitting the head of the bird and assuming the EXIF date and time recorded is accurate (0721.03.03.2020) and (assumed) the shot was pulled somewhere south of the Murray River and that sunrise in Melbourne, 03.03.2020 was 0707hrs – then:

---

William, I'm blown away by the level of sleuthing you've managed to achieve from that photo. You've almost pinpointed my current location... but that's not where the photo was taken. It was in the middle of the Drake Passage, around 3pm. I don't think I'd remembered to change the time settings on the camera. This may influence your calculations somewhat, but I dare say your appraisal of the shutter speed not being fast enough to freeze the motion is probably spot on. I was also on a little boat, rolling in sloppy seas, which undoubtedly added another element of motion. I'd considered going faster, but the light was very dim and the ISO already quite high, and the a6400 does not handle high ISO as elegantly as the a7s.

Quote:

---

Originally Posted by Bray

William, I'm blown away by the level of sleuthing you've managed to achieve from that photo.

---

You're welcome. Forensic Interrogation is one part of how I earn money. Info is in my Bio.

***

Quote:

---

Originally Posted by Bray

. . . but that's not where the photo was taken. It was in the middle of the Drake Passage, around 3pm. I don't think I'd remembered to change the time settings on the camera. This may influence your calculations somewhat, . . .

---

Understood. Thank you.

I assumed/guessed the image was taken in the southern area of AUS, probably near the Victorian seaboard because of the light TYPE combined with the assumed correct EXIF date & time AND the seagull type and the not extremely choppy water. (well you probably were lucky if it was actually was not very choppy)

If the date is correct then no, my conclusions stand: rationale - being further south than the Victorian seaboard and at about 1500hrs the EV range would be similar, i.e. EV 9~13.

***

Quote:

---

Originally Posted by Bray

. . . I was also on a little boat, rolling in sloppy seas, which undoubtedly added another element of motion. I'd considered going faster, but the light was very dim and the ISO already quite high, and the a6400 does not handle high ISO as elegantly as the a7s.

---

Understood. Thank you.

No matter how poorly any digital camera manages High ISO, its good to remember that any under-exposure at the taking of the shot will almost certainly result in a substantially poorer Final Image after the Post Production.

When using High ISO it is critical to nail the exposure, even push the exposure to the camera's limit: this is why I tend to make such a fuss about how critical it is for Photographers to understand exactly what the TTL Meter is reporting.

***

Quote:

---

Originally Posted by Bray

. . . - even the a7s struggled a bit at f/2.8.

---

As I understand this comment, it is about the camer's AF not attaining focus?

A thought, you were testing at SD = 1.5m and 3m. I believe your lens is equipped with a Focus Limiter, was it switched ON to Focus Limiting?

***

Quote:

---

Originally Posted by Bray

. . . A number of you have said it's less than ideal to shoot wide open on a long lens; a lesson now learned.

---

I am not sure that was exactly the advice.

I think there was two bits of advice about using a Telephoto lens wide open: one set of comments centred around the DoF may be quite shallow, if you're close to the Subject.

I think the other advice was to avoid shooting with the lens wide open when using a tele extender. This (in simple terms) is because nearly every lens made has poorer general IQ when wide open. The Tele-extender is another link in the optics chain, with its own (minute) IQ issues and therefore will usually always exacerbate any inferior quality in the lens.

As I alluded - I have done exhaustive testing with the x1.4MkII and MkIII and x2.0MkII and MkIII Canon Tele-extenders on the three EF 70 to 200 F/2.8 L Zooms. Very good results are possible, but very good results necessitate stopping the lens down (a bit).

Please see the two examples below. From memory they’re both pulled at an Effective Aperture = F/7.1, which is only ⅔stop down from the lens being wide open. Those two are made with a 5D Series Camera (probably the original 5D) and the EF 70 to 200 F/2.8L USM and the Extender EF 2.0MkII.

As mentioned, I haven’t used the Sony 70 to 200/2.8 and the Sony extender, so I have no idea what the limits are for that combination, I suspect (guess) that 1 stop down from the Maximum Aperture will show improvement – that’s another test you might like to do.

***

Quote:

---

Originally Posted by Bray

. . . - at the further distance (3m), the DoF was marginally shallower on the a6400 than the a7s ii - this was more pronounced at wider apertures. This is notable in that it's the smaller sensor, and confirms what was a gut-feeling in my original post.

---

This observation follows the Mathematics.

However this observation is only so, if you keep a fixed camera position and therefore the FRAMING of the two shots will be different for any given Focal Length you test.

IF you kept the same FRAMING for each photo (one using the 6400 and the other using the a7s ii) that would necessitate moving the Camera farther away from the Subject when you shot with the 6400.

If you do that test, then you will find that for any given Aperture and given Focal Length and the same Framing of the shot, the smaller format camera will provide a larger DoF.

WW

Footnote -

Two samples of 70~200 and x2.0 extender – please view them full size, in the lightbox.

https://d6d2h4gfvy8t8.cloudfront.net/10291553-orig.jpg

***

https://d6d2h4gfvy8t8.cloudfront.net/10291550-orig.jpg

All Images © AJ Group Pty Ltd Aust 1996~2020 WMW 1965~1996

Quote:

---

Originally Posted by revi

Of course, that's why it's a rule of thumb... ;).

You didn't even mention the physical condition of the user... I know that with at least of my lenses I have no chance to get a sharp image at the "rule of thumb" speed.
And I noticed that the minimum speeds mentioned by OP were at about that shutter speed, makign me think that that could have played a role in th elack of sharpness he sees.

---

It's possible, but you are primarily writing about camera movement here. Ignoring the other variables, when I look at some of the images, I suspect that we are looking at subject movement.

Digging back into the archives, this is a shot I took with a full-frame camera using a 500mm focal length, stabilized lens on a full frame body at 1/500th sec shutter speed. The osprey itself is sharp, but the wing tips are blurred. If I recall correctly, I did a bit of a crop here, so the problem is exaggerated a bit. So clearly the rule of thumb worked to get the bird sharp, but the wing tips were moving so quickly that they blurred.

https://live.staticflickr.com/5339/7...d9fc3520_k.jpg

Quote:

---

Originally Posted by Bray

I spent today photographing a diagonal line of AAA batteries, as Grahame and Dan suggested.

---

For the purpose of clarity my earlier suggestion to undertake testing using the batteries as targets was to confirm AF operation and confirm the field of focus (near/rear) was correct.

Quote:

---

Originally Posted by Bray

- while focus can be attained with the a6400 / 70-200 / 2x combo in a controlled testing environment, it's just not capable in the field (refer to the out of focus cockatoo photo). I won't be wasting time with this particular combo in the future.

---

To me there is something that does not add up here.

I often shoot with a 1.4 TC on a 400m, this combination giving a max aperture of f/8 and in very low light obtain accurate AF. But of course this is a different camera/lens and AF system.

Your reference suggesting that your "out of focus cockatoo photo" is an example of your rig not being able to attain focus in the field I believe is not correct. That photo is simply soft all over, a very significant crop of the original and there is nothing in it that confirms it's IQ is caused by a focusing error.

Quote:

---

Your reference suggesting that your "out of focus cockatoo photo" is an example of your rig not being able to attain focus in the field I believe is not correct. That photo is simply soft all over, a very significant crop of the original and there is nothing in it that confirms it's IQ is caused by a focusing error.

---

A critically important point that again brings me back to my earlier point: you are mixing together AF, DOF, and overall sharpness.

If there were a problem with the focus point, there would be some portion of the image that is crisply in focus. If there is a problem of insufficient DOF, there would still be a portion of the image that is crisply in focus, but it would be too narrow for your purposes.

DOF has nothing to do with the brand or choice of lenses. If you are having problems specific to your Sony rig, it isn't going to be DOF. The math is the same, regardless of brand.

Your table listed "no sharp focus" for a number of combinations. That cannot be a matter of DOF. As I mentioned, I do a lot of macro work, and in macro work, the DOF is so small that a crisp shot of a flower can require a composite of anywhere from 3 to 20 images, each with a different focal point. Everyone of those 3 to 20 images has a region that is crisply in focus.

If you are getting images with no sharp focus even with manual focus, then there are only two possibilities: other problems with the gear or technique. Several of these have been suggested: severe cropping, use of a 2X converter, and motion blur.

Here's a simple technique for evaluating problems with the lens/extender, e.g., elements out of alignment. Set up the camera on a tripod facing a plain brick wall, without the extender. Brick walls have fine detail and clear edges throughout. Use a remote release if you have one. If not, do it in bright light (to keep the shutter speed up) and trip the shutter gently. Set the camera to aperture priority. Then:

1. Focus manually, using live view and an enlarged view.
2. Take a series of shots, starting wide open and closing down one stop at a time.
3. Set the camera to AF, open the lens all the way, and take one more shot.

Then carefully examine the photos from #2 in order on screen, enlarging them. Start with the center and then examine all four corners. What you can expect to find is reasonable crispness in the center at all apertures but softer corners. This should improve as aperture is narrowed. The comparison between the first shot in #2 and the shot in #3 is a basic test of static AF.

Then repeat this with the extender added.

When I bought my first long lens (70-200mm f/4 Canon) I had some focusing problems. These were due to selection the wrong area of focus - letting the camera decide which area was in focus.

That was opeator error.

However, when Canon brought out the 70-300mm f.4.5-5.6 IS lens, it did have a mechanical/optical problem that caused unsharp images when it was extended to full zoom and shot with the camera in the vertical format. This was quite unusual and comments about it were all over the Internet which caused Canon to recall the lens and remedy the problem.

This was gear error...

However, this was a unique situation. Most often the problem with soft images are due to operator error rather than gear error...

One of the better definitions of DOF that I've read is this:

"Panotools sez:

A photographic image is only sharp in the focus plane. The farther an object is located in front of or behind the focus plane, the more it is blurred.

However, this blur is not recognizable if it stays below a certain amount. In classical photography which has a printed image as a goal (no matter whether digital or analog) the perception of the human eye is the limiting factor.

The human eye commonly accepts an edge as sharp, if the angle of view of the blur is smaller than 1 arc minute. Hence a point blurred to that amount has the diameter of 2 arc minutes, which is the same as 1/1700 of the viewing distance.

This is the allowed diameter of the so called Circle of Confusion (CoC). The normal viewing distance in classical photography is assumed to be equivalent to the printed image diagonal. The circle of confusion is the basis for most Depth of Field calculators or tables."

See more here: https://wiki.panotools.org/Depth_of_Field

Each paragraph follows based firmly on the previous one and there's no beating about the bush!

I hardly ever use published calculators because I am a) myopic and b) I only view on my monitor, not an 8x10" print held at 25cm from my nose.

Off-topic but I also use a CoC of one pixel-pitch to get a focusing distance for "virtual infinity" for a lens/camera combination ... Can be quite surprising for 5um and an 8mm lens! :eek:

Thanks for all these teachings. A few days of reading and practice shooting have revealed a few things:

- I tried Dan’s brick wall test with the 70-200mm lens (at 200mm only) and found focus at f/2.8 and even f/5 to be soft. The focus wasn’t pin sharp until f/8 (although I didn’t test the apertures between 5 and 8). Both AF and MF were soft at f/2.8. Adding the 2x teleconverter, both AF and MF were soft at maximum aperture f/5.6. Acceptable sharpness was attained at f/8. This suggests to me that there may be a problem with the internal workings of the lens rather than the autofocus.
- Practise photos revealed that the Auto and Tv exposure modes always try to set aperture to f/2.8 – which is too shallow for telephotos, and as discovered, my lens simply isn’t sharp at this aperture.
- Auto and Av exposure modes invariably select a shutter speed that’s too slow for handheld long-lens (ie. slower than the 1/focal length rule of thumb), which may be adding motion blur from either subject or photographer or both.
- The a6400 doesn’t have In Body Image Stabilisation (IBIS). I’d forgotten about this. It’s not an issue at wide focal lengths, but it almost certainly contributes to my inability to attain sharp handheld MF at telephoto focal lengths, and allows for camera movement motion blur to creep in.
- The a7s ii lacks Phase Detection Auto Focus, which is a big reason why the AF system on that model is so poor.

In addition, I’ve watched several hours of Mark Galer tutorials (huge thanks, Richard!) and have a much better understanding of the AF system in current generation models. It’s complex, to say the least. And little wonder I wasn’t winning, given the scant information Sony provides. But thanks to these tutorials and several days of practise, I can happily say that the AF system in the a6400 does work incredibly well, once you understand how all the settings should be used. No longer will I battle with manual focus for long-lens photography!

All this leads me back to my original post: my belief that my depth of field was too shallow for manual focus at long distances.
For the long end of the 24-105 lens, I think I can put the unsharp images down to inappropriately wide apertures or slow shutters or both, whether selected by me or by the semi auto modes.
But when I switch to the 70-200 lens, the focus becomes much harder to attain. I had put this down to the DoF decreasing as the focal length increased – which has been pointed out isn’t a thing, just an illusion. Illusion or otherwise, I believed the shallow DoF at long focal lengths to be the reason I couldn’t get the plane of focus to settle on the subject (or in some instances, couldn’t even achieve a plane of focus). It now seems my long lens issues are caused by a number of factors, all compounding each other:
- the 70-200mm lens probably has some form of internal damage that’s hampering its ability to achieve sharp focus at wide apertures
- the auto and semi-auto exposure modes select apertures that are too wide or shutters that are too slow for long-lens photography
- a lack of IBIS in the a6400
- attempting to manual focus whilst hand-holding because I didn’t understand how to use the AF system
- using a 2x teleconverter that reduces sharpness and might not be optically suitable for the a6400/70-200 combo, and
- my own inexperience at hand-held long-lens photography

Some are these are things I can fix. Getting more experience. Learning how best to use the Sony AF system, instead of manual focusing. Staying in manual exposure mode and dictating the aperture and shutter myself. And avoiding the doubler. I might also need to get the 70-200 lens examined and repaired, if necessary.

Keeping these things in mind is already paying off. Over the last few days, I’ve seen huge improvements in my ability to get sharp long-lens photos. Here’s one example (unprocessed). It’s shot at 200mm, f/6.3, 1/1000 sec, ISO 1600. I know the shutter needn’t be so fast and the ISO could therefore be lower, but the point is, a week ago there is no way I’d have been able to get a moving subject this sharp!!! Thanks for all your help and advice.

[IMG]https://live.staticflickr.com/65535/...e491a2a5_b.jpgDSC03054 by Braydon Moloney, on Flickr[/IMG]

Well done for persevering Braydon.

I looked at this image on your site where it can be viewed at a larger size. Sharpness is fine, and I base that on the hair which demonstrates what the gear is capable of. This is a far better test than 'brick walls' which we don't normally photograph so we are not sure what we should expect or hope for.

With respect to the softer results at wider apertures this can often be compensated for in post, and is normal.

With respect to your previous concerns regarding DoF you may find the below chart useful for showing what it would be with this image framing (assuming it's not cropped) at different apertures.

https://photos.smugmug.com/photos/i-.../i-Vg3zGfX.jpg

Glad to see that you are doing better Bray...

It is entirely frustrating not to get decently sharp images from a new camera.

I would contact Sony regarding your 70-200mm f/2.8 lens performance.

I should do a test to see what kind of sharpness I can get with my 70-200mm f/4 lens at varying apertures and varying shutter speeds, with and without OSS and IBIS...

Second thought: Have you done a micro adjustment with this lens?

https://www.sony.com/electronics/sup...icles/00020785

I have never seemed to have needed a micro adjustment on any of my lenses but, I have heard that many people have screwed up the AF of their lens trying to micro adjust while there are a number of folks who have improved the AF with micro adjustment...

With me - problems I have had with gear have usually been traced to operator error rather than a failing of the gear. However, I have had a 17-40mm Canon lens that was soft and was corrected by Canon under warranty. That is only one lens out of the many I have owned and used over the years...

A quote that haunts the Internet and is purported to be from a Nikon executive (although I have not ascertained if there ever was such an announcement from any Nikon exec) is paraphrased; "If you are not getting very good to excellent images from your modern digital camera of any brand, he fault most likely is your technique..."

As an example - early on, I had difficulties using the focus and recompose technique. I learned that I had the camera AF in continuous AF and the focus was shifting as I recomposed... My Sony cameras, especially with continuous AF combined with Eye-AF have solved that problem...

Quote:

---

Originally Posted by Bray

Thanks for all these teachings. A few days of reading and practice shooting have revealed a few things:

- I tried Dan’s brick wall test with the 70-200mm lens (at 200mm only) and found focus at f/2.8 and even f/5 to be soft. The focus wasn’t pin sharp until f/8 (although I didn’t test the apertures between 5 and 8). Both AF and MF were soft at f/2.8. Adding the 2x teleconverter, both AF and MF were soft at maximum aperture f/5.6. Acceptable sharpness was attained at f/8. This suggests to me that there may be a problem with the internal workings of the lens rather than the autofocus.

Quote:

---

Richard wrote: I would contact Sony regarding your 70-200mm f/2.8 lens performance.

---

---

Braydon, there may not be a problem with your particular example of that model lens. It is well known that the great majority of lenses can be a little soft wide open and that they do sharpen up when stopped down to an oft-quoted f/4 to f/8.

An example:

https://www.wrotniak.net/photo/tech/...tozone-mtf.gif

https://www.wrotniak.net/photo/tech/mtf.html

That one looks pretty good. This one is more typical:

https://www.lenstip.com/upload2/239693_roz1.png

Click on the image to see the numbers better, or go here:

https://www.lenstip.com/574.4-Lens_r...esolution.html

A test:

http://bobatkins.com/photography/tec...tion/macro.jpg

http://bobatkins.com/photography/tec...ffraction.html

"You can see here that sharpness increases as you stop down (an indication that aberrations are present at wider apertures)."

HTH

Braydon,

I'm impressed by your perseverance and delighted that you are making progress.

I'm having a little trouble tracking what you are doing because you are posting about 4 things (I earlier said 3) that contribute to sharp focus: the AF system, technique (manual focusing, camera movement), the quality of the lens at different apertures, and DOF. These are all different.

Re the brick wall technique: what this offers that examining a shot of a person's hair doesn't is a very clear way to see how much sharpness falls off from the center of the image to the corners. I also find it a reasonably good way to examine focus at any one point, although not as good as a focus chart. For example, mortar has sand mixed in, and you can enlarge the image to see whether that is clear.

As Ted and Grahame have pointed out, it is normal for lenses to be less sharp when wide open, and that lack of sharpness is likely to be exacerbated by the use of an extender. It varies from lens to lens, but the sharpest point is usually between f/5.6 and f/8.0, often toward the higher (narrower) end of that range.

Re microadjustment: I may be wrong, but I believe that if your camera uses contrast-detection AF, microadjustment isn't relevant. It's used to adjust for differences in the light path to the sensor and to the AF detection sensors in phase detection AF systems.

You wrote:

Quote:

---

All this leads me back to my original post: my belief that my depth of field was too shallow for manual focus at long distances.

---

Not possible. For example, DOF on your camera using a 200mm lens at 20m and f/2.8 is well over a meter. That's more than ample for obtaining sharp focus manually. I think here again you are mixing some combination of the four issues I listed above. Which camera you use is relevant only because of the sensor. In other respects, DOF has nothing to do with the brand of camera or lens.

Quote:

---

- Practise photos revealed that the Auto and Tv exposure modes always try to set aperture to f/2.8 – which is too shallow for telephotos, and as discovered, my lens simply isn’t sharp at this aperture.
- Auto and Av exposure modes invariably select a shutter speed that’s too slow for handheld long-lens (ie. slower than the 1/focal length rule of thumb), which may be adding motion blur from either subject or photographer or both.

---

If you use auto-ISO, this could happen, depending on the program coded for that camera. However, I almost never do use auto-ISO, and with a fixed ISO, this doesn't happen. If you fix ISO and pick a given shutter speed in Tv mode, the camera will pick whatever aperture gives you the right exposure, and vice-versa with Av mode. I strongly suggest fixing ISO because doing so will give you back some of the control you need to deal with the issues you are having.

Sorry if I sound repetitive, but I strongly suggest you try to isolate these four issues. The reason I suggested manually focused images using a tripod is that this removes 3 issues (AF, technique, and DOF) and will allow you to test the quality of the lens, with and without the extender. It will also show you the impact of aperture, which is to be expected with any lens.

If the equipment seems OK in this first set of tests--and I increasingly suspect that it will--I would then move on to dealing with one of the remaining 3, in isolation. For example, using a tripod and manual focus again, take another set of images, this time of something that is not parallel to the sensor--e.g., a fence running diagonally. This will allow you to understand the effects of aperture on DOF.

A third test, also on a tripod, could evaluate how well AF is functioning under various conditions.

then, finally, you can work on technique, e.g., ways of holding the camera to minimize motion blur.

Dan

Do not be afraid to shoot wide open at long focal lengths. The f/2.8 70 - 200mm lens is definitely in most portrait photographer's camera bags. One doesn't buy "fast glass" and then shoot it at f/8 or f/11; one buys it to shoot wide open and to take advantage of the shallow depth of field it produces. In fact the "pro" glass is designed to be shot that way.

As with all things, practice, understanding your equipment, your subject and using strong photographic technique (there is a "right way" to hand hold for long focal length images) is important. It looks like you are getting there, based on the image you show in #30.

The other "rule" that one has to be careful with is selecting the appropriate ISO setting. The lowest ISO that works for the shot is usually best, but I will sacrifice ISO any day to ensure that I have the appropriate shutter speed and aperture. Blurred images usually should be thrown out, but images with digital noise that are sharp can generally be fixed in post processing.


https://live.staticflickr.com/65535/...650d579e_k.jpg

Nikkor f/2.8 70-200mm lens shot at a 200mm focal length using an aperture of f/2.0l ISO 640 and shutter speed of 1/500th second

Quote:

---

Originally Posted by Bray

I tried Dan’s brick wall test with the 70-200mm lens (at 200mm only) and found focus at f/2.8 and even f/5 to be soft. The focus wasn’t pin sharp until f/8 (although I didn’t test the apertures between 5 and 8). Both AF and MF were soft at f/2.8. Adding the 2x teleconverter, both AF and MF were soft at maximum aperture f/5.6. Acceptable sharpness was attained at f/8.

---

"Focus" at f2.8 or f5 cannot be "soft" by itself. It will either be correctly focussed or it will not be. If your image from a correctly focussed shot at f2.8 or f5 is "soft" that is a problem with the lens, or a problem with your technique. Even possibly a problem with the camera.. It may be the lens is incapable of providing you with the sharpness you require.

Quote:

---

Originally Posted by Bray

Practise photos revealed that the Auto and Tv exposure modes always try to set aperture to f/2.8 – which is too shallow for telephotos, and as discovered, my lens simply isn’t sharp at this aperture.
- Auto and Av exposure modes invariably select a shutter speed that’s too slow for handheld long-lens (ie. slower than the 1/focal length rule of thumb), which may be adding motion blur from either subject or photographer or both.

---

Welcome to the exposure triangle! There is no magic answer to this. If you want to take a picture of an object using a high shutter speed and a moderate aperture and a low ISO...then you need good light. Otherwise you need to make compromises.

Quote:

---

Originally Posted by Bray

All this leads me back to my original post: my belief that my depth of field was too shallow for manual focus at long distances.
For the long end of the 24-105 lens, I think I can put the unsharp images down to inappropriately wide apertures or slow shutters or both, whether selected by me or by the semi auto modes.

---

Sharp focus and DOF are two separate subjects. Often interlinked but completely separate. Indeed a large DOF can mask incorrect focus techniques.

Quote:

---

Originally Posted by Bray

- the auto and semi-auto exposure modes select apertures that are too wide or shutters that are too slow for long-lens photography

---

No. The camera is trying to give you the best exposure it can manage in the circumstances you present to it. It cannot perform magic.

You are doing the right thing by practising as much as you can. But remember there will be some scenes that cannot be captured as you would wish because of the available light.

One further thing to add. Every lens has its sharpest aperture. This is an aperture which renders the Focus Point at the sharpest the lens can deliver. It is called MTF. It is often 2 stops down from wide open but will vary especially with zooms.

But again, do not confuse this with DOF. A lens when stopped down will deliver a DOF wider than when wide open. But this has nothing to do with MTF.

Quote:

---

Originally Posted by pschlute

One further thing to add. Every lens has its sharpest aperture. This is an aperture which renders the Focus Point at the sharpest the lens can deliver. It is called MTF. It is often 2 stops down from wide open but will vary especially with zooms.

---

Thank for confirming my post #33, Peter, viz.

"It is well known that the great majority of lenses can be a little soft wide open and that they do sharpen up when stopped down to an oft-quoted f/4 to f/8."

Just to clarify, I am no longer blaming my long focal distance focusing issues on the DoF.

Quote:

---

All this leads me back to my original post: my belief that my depth of field was too shallow for manual focus at long distances.
... [rambling explanation of why I initially believed it was DoF causing the problem] ...
It now seems my long lens issues are caused by a number of factors, all compounding each other:

---

Perhaps I should have finished that last sentence with "..., not depth of field as initially perceived"

I am glad that you see progress. That's fantastic.

***

There is much quality information and excellent advice in this conversation.

Mostly always the advisors and the advice has been specific to: ONE particular matter.

Advice and commentary in a big bundle can be read “in a big bundle”. I advise against that approach.

I suggest that you isolate the advice into small bits and deal with it according to its subject content.

Above all else – this below, in my opinion, is the primary and overall guiding piece of advice which you should follow -

Quote:

---

Originally Posted by DanK

. . . you are posting about 4 things (I earlier said 3) that contribute to sharp focus: the AF system, technique (manual focusing, camera movement, [Subject Movement etc]), the quality of the lens at different apertures, and DOF. These are all different.
. . .
I strongly suggest you try to isolate these four issues.

---

WW