DOF question

Landscapes are one of my favorite subjects and I like to shoot FF because of the greater resolution but I tend to have more issues with DOF vs 1.6X crop.

Here's an example....

40D, 28mm, f/13, focus on post in front...

The smaller format camera with its shorter focal length is going to provide a greater depth of field than the larger format camera with a longer focal length (with both focal lengths chosen to provide the same framing with the cameras in the same location and both using the same aperture). That's an indisputable fact.

If you're trying to get everything in focus, you need to choose a target for focusing on that's further away than the fence. In other words, you want to find a focusing target at the hyperfocal distance.

For the 5D with 50mm at f/16, that focusing distance would be about 21 feet from the camera. According to this DOF calculator that would provide acceptably in-focus results from 10.4 feet to infinity.

With a 50D fitted with a 31mm lens at f/16 (the closest field of view match to the 5D/50mm combination), the hyperfocal distance would be 10.5 feet. That would provide acceptably in-focus results from 5.25 feet to infinity.

Read up on hyperfocal distance. I never set my lens higher (normally) than 8-11. Images start to get softer and I think all lenses have optimum aperture a few stops higher than it's widest.

Have to say I never mastered or did enough testing using the above method. I still need to learn more...

Sussex Wedding Photography
State Of Mind Photography

I wish people would stop pixel peeping and enjoy their works of art in their entirety..

yogestee wrote in post #11074882
I wish people would stop pixel peeping and enjoy their works of art in their entirety..

^^^^^The voice of reason

I have a 16"x20" print hanging on the living room wall that may be 50% of the frame shot with a Nikon D50 6MP, the print looks very good the file I sent to the print looks sort of crappy at 100%

Jim

he only provided those to illustrate his point that the DOF is different as some people may not be able to tell the difference from the original.

SkipD wrote in post #11074522
The smaller format camera with its shorter focal length is going to provide a greater depth of field than the larger format camera with a longer focal length (with both focal lengths chosen to provide the same framing with the cameras in the same location and both using the same aperture). That's an indisputable fact.

If you're trying to get everything in focus, you need to choose a target for focusing on that's further away than the fence. In other words, you want to find a focusing target at the hyperfocal distance.

For the 5D with 50mm at f/16, that focusing distance would be about 21 feet from the camera. According to this DOF calculator that would provide acceptably in-focus results from 10.4 feet to infinity.

With a 50D fitted with a 31mm lens at f/16 (the closest field of view match to the 5D/50mm combination), the hyperfocal distance would be 10.5 feet. That would provide acceptably in-focus results from 5.25 feet to infinity.

I appreciate the response Skip, and that certainly is the most accurate way of doing it, but its not like I have a measuring tape when I'm out shooting.

dariussutherland wrote in post #11074629
Read up on hyperfocal distance. I never set my lens higher (normally) than 8-11. Images start to get softer and I think all lenses have optimum aperture a few stops higher than it's widest.

Have to say I never mastered or did enough testing using the above method. I still need to learn more...

Sussex Wedding Photography
State Of Mind Photography

On FF I shouldn't need to worry about seeing the effects of diffraction until f/16 or more. Do you shoot landscapes?

yogestee wrote in post #11074882
I wish people would stop pixel peeping and enjoy their works of art in their entirety..

team haymaker wrote in post #11075199
he only provided those to illustrate his point that the DOF is different as some people may not be able to tell the difference from the original.

Exactly. I showed the crop to illustrate the fact that the silo was out of focus in the FF shot, that's all.

Anyone have any other useful "in the field" tips to getting lanscapes completely in focus on FF?

versedmb wrote in post #11078021
<snip>

Anyone have any other useful "in the field" tips to getting lanscapes completely in focus on FF?

This is how I do it. Quite simple really, with these few numbers written inside the lens cap of my 17-40L lens. Data from www.dofmaster.com and note that these relate to full frame; crop format is different.

HFD..........f5.6.....​..f11......f22
17mm......5.6ft.....2.​8ft....1.4ft
24mm.....11.2ft.....5.​7ft....2.9ft
35mm......24ft.......1​2ft......6ft

The reality of hyperfocal distance focusing is that it only really applies to wide angles and landscape photography. And because the real world use of depth of field is not nearly so exact as the numbers might lead you to believe, it is easily possible to estimate the inbetween settings.

One of the key things to know about HFD focusing is that the near point of the hyperfocal range is always exactly half the HFD, ie HFD 10ft, everything sharp from 5ft to infinity.

This is how I do it in practise - landscape with distant mountains and a nice rock formation in the foreground. Frame it up at 24mm, and visually estimate that the nearest rock I want sharp is 6ft away. I therefore know that the hyperfocal distance I need is double that at 12ft, and I will normally use AF (centre point, focus-recompose) to focus on something which I visually estimate is twice as far away as that nearest point. This is very easy to do, and completely avoids the need to refer to any distance scales on the lens, which are often not much help. Then inside my lenscap, 12ft corresponds pretty closely to f/5.6. Job done

Just one more thing. HFD focusing can be quite controversial, and one objection is that by definition what it does is put infinity right at the extreme limit of acceptable sharpness. If those distant snow capped mountains are maybe the most important thing in the shot, then you need to make sure they are very sharp indeed, rather than just sharp enough. There are various ways of addressing that, but one of the simplest is just to use a higher f/number than the one suggested, in the case above, set f/8 instead of f/5.6.

Here is the inside of the lens cap in question, same as the one on my 24-105L, which has also got a few regular depth of field reminders on there. I hope the numbers are readable, because when you notice that there is a lot of halving and doubling and squaring going on, it's easy to work out what the DoF is for 25mm and 200mm with a bit of mental arithmetic.

versedmb wrote in post #11078021
I appreciate the response Skip, and that certainly is the most accurate way of doing it, but its not like I have a measuring tape when I'm out shooting.

The key is to learn the approximate values for different apertures for selected focal lengths. The idea of jotting down notes to keep in your bag or even - like shown in a post above - in the lens cap is a good one. You can easily estimate the distances involved and that would be plenty accurate.

SkipD wrote in post #11079019
The key is to learn the approximate values for different apertures for selected focal lengths. The idea of jotting down notes to keep in your bag or even - like shown in a post above - in the lens cap is a good one. You can easily estimate the distances involved and that would be plenty accurate.

The key point about what I posted above, is that you don't need to be able to estimate distances too acurately, or depend on the markings on the lens focusing scale which are usually pretty unhelpful.

As mentioned above with HFD setting, whatever the subject in the foreground is that you want sharp, then just focus on something that is twice as far away. Use centre-point AF and focus-recompose technique (which I use for pretty much everything anyway). That's your HFD set.

The only bit of estimating you need to do is then take a stab at how far away that focus point is. Maybe the focusing scale will, with luck, have a number that you can read off, but if it's fairly close, then it's quite easy to guess accurately enough. If it's further away, then you don't have to be so accurate as DoF increases with distance. And if in doubt, use one f/number higher and you'll cover it anyway.

Hoppy1,

Thanks for the reply - just what I was looking for.

DOF Calculators all assume that the print being viewed is an 8x10 print from a distance of about 10". When you greatly enlarge one portion of the print, like you did. all DOF calculations obtained earlier are invalid. The only thing you really proved is that FF has less DOF than APS-C. The size of the Circles of Confusion, being magnified by the pixel peeping, are more detectable by the eye so you will see thing as 'out of focus' when they would otherwise have been acceptably small (to fool the brain into thinking it is still seeing a sharp point, not a disk) in the 8x10 print viewed from 10".

As egraphdesign said, "the print looks very good the file I sent to the print looks sort of crappy at 100%"