[pschlute]

My understanding is OP is trying to understand why one would benefit from FF if you don't want shallow dof. The scenario illustrated pits the lost ISO vs the benefits of a large sensor.

Yes I think you are right. I happen to think he is overthinking things. There was a recent thread on here where folk were asked to guess which pics were FF and which were aps-c. The results were no better than chance.

Perfect portraits can be made using aps-c or FF, high ISO or low ISO, wide aperture or narrow, a great portrait lens or an old milk bottle. Technique is what is important.

[stevebrot]

Am I wrong? What do you think?

Take some photos with the intent to prove yourself wrong.* There are a ton of assumptions being floated here...enough to generate, perhaps, at least a hundred pages of opinions regarding format/focal length equivalence followed by as many more of rebuttals, all without a single photo being taken to test.


Steve

* Ironically, this is a core tenet of the scientific method.

[normhead]

My understanding is OP is trying to understand why one would benefit from FF if you don't want shallow dof. The scenario illustrated pits the lost ISO vs the benefits of a large sensor.

I's the same, ƒ8 on FF is the same DOF as ƒ5.6 on APS-c. The difference being you get a higher shutter speed with AP-c. The benefit to the FF is at base ISO you have more dynamic range.

1000 questions, same answer.

[photoptimist]

Let me put a concern of mine: if a 36x24 sensor can mimic the results of a 24x16 sensor with more benefits.

......


What do you think?

Consider this pair:
A K-5 w 50mm set to f/2.8, 1/200sec, ISO100
A K-1 w 75mm set to f/4, 1/200sec, ISO200

They'll have identical exposure, motion blur, DoF, and overall DR. However, the K-1 image will probably have better sharpness both because it has more than 2X the pixels and because the lens is being used closer to it's sweet spot of maximum resolution.

Overall, you'll find that the K-1's higher DR, better color accuracy and higher resolution really do offer some advantage beside shallow DoF. Whether that better DR and resolution is "worth it" to you depends on you.

[Serkevan]

Most of my pictures are taken in good enough light that one aperture stop is not going to make the shutter speed unusable. Going from 1/500 to 1/250 for a portrait is no biggie...

[othar]

If I set aperture at f/2.8 I would not have the depth of field I like, it would be shallower. So I will need to step down lets say one stop. But then I could not keep the ISO at 100 but I would need to step up at ISO200. Then the benefit of the 36x24 sensor having one stop more benefit in sensitivity is evaporated. Dynamic range of ISO200 of the 36x24 sensor may be in comparison with ISO100 of the 24x16 sensor.Am I wrong? What do you think?

Yes, you would need to stop down your ~75mm lens 1 or 2 stops (I don't know the exact calculation by heart) further down to get the same depth of field. It is a newer sensor so ISO100 on the K-5 will not really give you more dynamic range as ISO 200 or 400 on the K-1 (although pixel density is a little higher on the K-1) -> you won't see a real difference though. But you might benefit from more MP (36 against 15) with the K-1 (for large prints but also retouching and the like in PP).
While this might be an interesting intellectual game, there are other benefits of the K-1 that can give you a reason to buy it.

[swanlefitte]

My apologies to the OP. You touched on a forum nerve, I hope you get what you came for. Don't be put off by the minutia, read between the lines. You got an answer at soo many levels it hurts. pick the one that suits you.

I's the same, ƒ8 on FF is the same DOF as ƒ5.6 on APS-c. The difference being you get a higher shutter speed with AP-c. The benefit to the FF is at base ISO you have more dynamic range.

1000 questions, same answer.

I would love if you took the time to to do an "extreme" conditions test where it should be obvious between the formats. Maybe we need a Go Fund Me. If we could fund it, it would be great to see every condition people say it is obvious between the formats and see how well it holds up. I suspect we would see a gradient by conditions. Extreme parameters would yield clear results and non-extreme parameters would yield no statistical difference.

The OP's example is slightly extreme in that the low light forces the shutter to be 200 max to stop motion(I assume) while being able to open up to f/2.8.
Scientific controls must be established that
200 is sufficient to stop blur.
less than 200 cannot stop blur.
there is no shutter shock which causes said shutter of 200 to be lower.
The light cannot be turned up.
That ISO of 200 will affect picture quality more than shutter of 100.
The difference of ISO 200 to 100 vs shutter of 100 to 200 must be established.
Other.

We will then be able to possibly determine an advantage or disadvantage to this specific scenario.

[biz-engineer]

Equivalence of format subject here. Equivalence works until the glass isn't fast enough in low light, or until the glass doesn't resolve enough for the wanted enlargement.

I think it's useful to have an f/1.4 lens because it's "faster" and will work better in lower light. My only observation about what OP's said is that depth of field depends a lot on distance from the subject. So if all he ever wants to do is portraiture in a studio at a relatively fixed distance, then he can get a lens optimized for that at whatever maximum aperture suits that application. But for more general purpose stuff (e.g., walking through the "historic district" taking pictures of an old building down the street in the late afternoon) then a wider aperture would be a good thing.

[Hidrieus]

You're thinking too much. Take some pictures at different apertures, select the best. Find out where you like each lens individually. And stop being so critical about what shutter and ƒ-stop to use. It looks like me like you've set restrictive parameters that are interfering with your ability to get the image you want. For a portrait, there's no reason to set the aperture at ƒ2.8, there's no reason to set the speed at 1/200. All you're doing here is causing yourself grief.

I have to stay at 1/200sec because my subject performs an act and does not stay still. f/2.8 is what I have found is most pleasing blurring but still recognizable background for the scenery my subject usually performs (indoors).

[StarTroop]

My requirements for a digital camera when I was looking to pick up photography as a hobby was basically just that the IQ must match or exceed the affordable film I was used to using. By that standard, in my opinion crop sensors cameras have already surpassed that expectation. So, from my perspective the relative increased DoF at equivalent focal lengths is a pure bonus, considering there is typically no issue or difficulty in achieving a proper exposure due to the limitations of a crop sensor versus a full-frame sensor. Never before have I felt like if I had only one stop more of usable dynamic range I would have pulled-off a difficult shot, but plenty of times have I missed focus due to using a wider aperture than I like to use. I'd rather increase ISO or rely on SR/tripods than open up aperture simply for exposure purposes, and I almost never intentionally blur backgrounds. In my experience, f/2.8 to f/8 is acceptable on any wide/normal prime in any situation that is a least dimly lit (like night street photography), which makes the DA Limiteds pretty much the perfect balance of form and function on the APS-C format.

[normhead]

I have to stay at 1/200sec because my subject performs an act and does not stay still. f/2.8 is what I have found is most pleasing blurring but still recognizable background for the scenery my subject usually performs (indoors).

If you can't change the parameters, then the only thing you can change is the lenses, experiment with different focal lengths. Indoors you really have to go to a higher ISO. AN FF camera will give you better noise performance at high ISO. But you're in a box. Higher ISO and good noise reduction software may be your best option.

Unless you have extremely high contrast in the space where you shoot, you should be easily able to go to 400 ISO without a noticeable loss in DR. That gives you a few more stops to play with.

[reh321]

Unless you have extremely high contrast in the space where you shoot, you should be easily able to go to 400 ISO without a noticeable loss in DR. That gives you a few more stops to play with.

If you have a KP you can go many times higher than 400 and still have sufficient DR.

[biz-engineer]

I's the same, ƒ8 on FF is the same DOF as ƒ5.6 on APS-c. The difference being you get a higher shutter speed with AP-c. The benefit to the FF is at base ISO you have more dynamic range.1000 questions, same answer.

I discovered equivalence work better than I orginally thought. And with lenses MTF generally drops 20% from center to edges, so it doesn't really matter how large is the sensor, you never get those 20% back, except by stitching panos that one can always do whatever format is used.

[mikesbike]

The extra or bigger pixels are gone.

Well, wait a minute- they are not gone from the area of the frame that is of interest. If the advantage is not present in every part of the frame, what good is it?

---------- Post added 10-14-19 at 05:03 PM ----------

Let me put a concern of mine: if a 36x24 sensor can mimic the results of a 24x16 sensor with more benefits. Suppose I have a 50mm lens on my K5. I want to shoot at f/2.8 and 1/200sec ISO100 for a portrait. I personally do not like on my K5 24x16 sensor too sallow depth of field for portraits. I want both eyes in focus, if the ear and the nose are in focus even better. So I do not go larger than f/1.8 in my 50mm. A f/1.4 50mm lens would be useless to me, I have tried them in other APS-C cameras and found the depth of field annoyingly shallow and the bokeh is just an undistinguishable mesh. So to replicate the before mentioned set with a 36x24 sensor I would need a pricier 75mm lens, probably available will only be a 80mm. Time kept at 1/200sec. If I set aperture at f/2.8 I would not have the depth of field I like, it would be shallower. So I will need to step down lets say one stop. But then I could not keep the ISO at 100 but I would need to step up at ISO200. Then the benefit of the 36x24 sensor having one stop more benefit in sensitivity is evaporated. Dynamic range of ISO200 of the 36x24 sensor may be in comparison with ISO100 of the 24x16 sensor.
Am I wrong? What do you think?

It seems to me, since your question reflects a desire to increase DOF, if you are considering going to a FF body, you are fishing in the wrong waters. A FF body is capable of reducing DOF compared to your APS-C body, not increasing DOF. In any case, as others have said, you could simply increase your ISO a bit and close down aperture a bit more for increased DOF. Your K-5 is a very capable camera for low noise and high retention of detail and resolution well up into the range of ISO. It also has one of the best sensors for dynamic range among APS-C models.